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GMC Data Report No. 348
Skarns anal ore deposits of the Whitehorse Copper Belt, Yukon Territory, Canada: Some aspects of petrogenesis and mineralization at the Arctic Chief, Little Chief, and Biack Cub South localities. t ~~ ~~ d ,! ~ S Y 'yyyr3fff fl a-- ~.e~ } 1 iGt} ~ s ~~~ ~ Sri :~~'F'~ j ~~~• • `~ ` ti~ Received 10 December 2007 Total of 127 pages in report Alaska. Geologic Materials Center Data. Report No. 348 SKARNS AND ORE DEPOSITS OF THE WHITEHOR5E COPPER BELT,- YUKON TERRITORY, CANADA: 50ME ASPECTS OF PETROGENESIS AND MINERALIZATION AT THE ARCTIC CHIEF, LITTLE CHIEF, AND BLACK CUB SOUTH LOCAI_tTIES ' _ (PART 1 OF 2) Thomas C. Mowatt (1) June C. Mowatt (2) October 4, 2007 (1 } Geologist, ..and Senior Associate, On-Line Exploration Services Inc., Anchorage, Alaska; c/o .Post Office .Box 1438, .Haines, Alaska 99827 USA (2) Geologist (Deceased, 1992) GMC DATA REPORT'. ~3 4 $ Page 1/127 PREFACE As reflected by the revised title, "Part 1 °' of the present report represents a somewhat more expanded version of "Part 1" of Mowatt; T. C: and J. C. Mowatt, 2007,. Investigations of Some. Mineralogical,. Petrological, Geochemical, and Geological Relationships at the Arctic Chief {West) Locality, Whitehorse Copper Belt, Yukon Territory, Canada; Alaska Geologic .Materials Center Data Report No. 344,.. Eagle River, Alaska, 136 pp: It was prepared in .response to queries, comments, points. raised, and. suggestions, .from a number of interested individuals who had read the original "GMC#344" version. This "revised" version is intended to present additional material,- discuss in more :detail interpretive aspects of petrogenesis and related mineralization at the Arctic. Chief ore deposit,. as well as other ramifications of our research. As well,. comparisons with other localities in the Whitehorse Copper Belt are discussed, as feasible...In particular, we also report here on .our. earlier recognition, and confirmation, of the- presence of periclase.(brucite) marbles in specimens from. the Little Chief and the Black Cub South ore deposits. To .our knowledge, representing the initial confirmed report of periclase (brucite) marble at either of these: other .localities. Which is noteworthy in itself, of course. Various ocher remarks are, put forward, here and there, in this .version, on topics/aspects which vuere .deemed deserving of the attention not given them, due to time factors, in our previous GMC#344 report.. This present report thus is supplemental to the somewhat more descriptive, fundamental treatment offered in Part. 1 of GMC#344.. While Part 2 of the latter, the "Data Supplement°, has been slightly modified accordingly, as well. Represented by a new "Part 2", under the revised title. Though remaining essentially as basic background information relevant to our investigations. This presents additional information, including sketch maps showing .general locations. of sample sites, abstracted field notes, results of 30x/60x stereo- microscope examination of samples, petrographic microscope .examination of selected materials as grains-in-oil, analyses and other comments. Due to convergence of circumstances (time/age, space/distance, .funds, "world. affairs"), this report has been prepared. solely by the first author. For the same reasons it 'has been neither edited nor reviewed independently (other. than informally via the above-.mentioned.. readers). Nor has S. M: Aleksandrov had the opportunity to do so either.. Many valuable written comments were offered to the first author by Dr. Aleksandrov :.during the course of his studies of samples sent to him representing various aspects of the Arctic Chief locality. Selected comments presented herein are set within full quotation marks. Though of course these are not .necessarily "attributable", strictly speaking, given the ever-present "context", language problems, etc. in such matters, as well as the overall circumstances attendant to working "across-the-miles". However, his recent paper "Gold Behavior during Endogenic and Supergene Alterations of Sulfides in Magnesian Skarnsn (published in Geochemistry International, volume 45; number. 2, pages 152-i69, 2007) affords direct access to some of his views. as related to magnesian skarns, and our investigations of the, Arctic Chief locality.. Thus responsibility for the contents of the present paper remains with the first author: Including,. in particular, for various "interpretations°, etc., based on previous communications with Aleksandrov. The first author may be contacted at the Haines, Alaska mailing address given above. AMC DATA REPORT 3 4 $ Page 2/127 ABSTRACT Investigations of certain. geological aspects of the .Whitehorse Copper Belt, Yukon Territory, Canada .were initially pursued during 1980-1982, and subsequently continued,- after a hiatus of some twenty-two .years, :during 2004-2007. Principal ultimate concerns were with regard to petrogenesis-and associated mineralization.. The initial work resulted in the (then) first-known recognition, and con#irmation, of the "magnesian-skarn" character of the. Arctic Chief (west) locality. Analytical procedures featured stereo-microscopic sample .examination, petrographic as well as ore microscopy, x-ray. diffraction, and x-ray emission (fluorescence) spectrometry. At this localiity (as weH as sites at Little Chief, and Black Cub South), a key feature, also initially recognized .and confirmed at than time, was the occurrence. of "periclase (brucite) .marbles", with "classic" examples of the type present.. Other: significant features at the Arctic .Chief characteristic of magnesian skarns -- initially identified as such -- included .rocks of "calciphyre° character, the presence. of a number of other magnesian minerals (in addition to pyroxene[s]) -- including forsterite, serpentine~> spine), phlogopite, Mg-chlorite, talc, ciinohumite(?) --, and the presence of typical "rhythmic banding", or its vestiges, in rocks, as well as in "ores". In addition, the {quite) speculative. presence of Mg-Fe borate minerals of the ludwigite-vonsenite series was indicated, though this remained unconfirmed at that time. ` Unfortunately, this .initial work remained unreported,. formally, at the time. The subsequent work (2004-2007). provided an expanded sample base. Some one hundred selected specimens were sent to S. M: Aleksandrov at the •Vernadsky Institute, Russia, for use in his own research... His subsequent definitive. work on them confirming, as well as significantly extending, our previous findings. Providing confirmatory. evidence for the formation of the borate mineral magnesian-ludwigite {pseudomorphously replaced by magnetite) at the Arctic Chief : As discussed in a portion of a paper by Aleksandrov in Geochemistry .International, {2007). The Arctic Chief (west) locality is demonstrably an example of a "magnesian-skarn". Additionally, our work, collectively, has shown .that. it features a version of "primitive-type zoning", formed under. conditions of the "hypabyssal periclase facies", as considered in the context of the model of skarn-formation devetop~~d andrefined by Aleksandrov- and co-workers. This .approach merits consideration regarding the nature and origin(s) of "skarns", particularly .with, regard to those associated with "host" rocks of "dolomite) dotomitic/ . magnesium-rich" character. It offers a conceptual, as well as substantively based, framework of .theoretical background, fundamental knowledge, and experimental work. As well, it affords ample evidence, from a wealth of experience and .analytical work, supportive of the validity of this. approach to the genesis of skarns. Including our work on the Arctic Chief.. Appreciation, -and utilization, of this model ought to be an essential aspect of investigations intended to further. the understanding of such geological occurrences. In turn, .potentially .yielding. insights of "more practical° value in the exploration for, evaluation of, .and production of mineral resources from deposits related to magnesian skarns. Such. as has been the case in many areas, worldwide (cf. Aleksandrov: 1998, and numerous other publications). Our. 2004-2007 investigation also resulted in the recognition of some interesting occurrences . of molybdenite, and. other mineralization, near the Arctic Chie#. Implications of any/all of the above points, local6y, elsewhere in the Whitehorse Copper Belt and environs, as well as elsewhere regionally, remain to be evaluated. 1 GMC C~ATA REPORT 3 `4 $; Page 3/127 PART 1: Introduction; studies, results, interpretations, discussion; summary and conclusions; acknowledgements; references. INTRODUCTION: A study of the Arctic .Chief locality/ore deposit, in the "Whitehorse Copper Belt", Yukon Territory, Canada (cf. Tenney, 1981; Watson, 1984; Morrison,1976, 1981; Heon, 2004; Meinert, .1986; Wheeler, 1961;- Kindle, 1964; Grabher, 1974; Dawson and Kirkham, 1996, Aleksandrov, 2007; etc.), was initiated by the first author ("TCM") and the second: author. ("JCM") during .1980-1982 (cf. Mowatt and Mowatt, 1982}. At the time, TCM was .employed as Supervisory Geologist, Alaska Field Operations Center, Bureau of Mines ("USBM"}; .United States Department of the Interior, Douglas (Juneau), Alaska. The intent was to attempt to add to the understanding of the nature of this "skarn-type" ore deposit,. by investigating various aspects of the mineralogy, petrology, geochemistry and geological relationships. The goal being public dissemination of such. knowledge as might be gained, per the Bureau's charge as "....... a research and information organization, concerned with matters related to mining and.. mineral resources...... ", as well as utilizing this, knowledge in other .USBM .mineral resources-related activities elsewhere,. especially in Alaska. Of particular interest were a number of key features of deposits elsewhere of "contact- metasomatic magnesian skarn-type". As recognized and elucidated over the course of a number of years by the ,extensive -- and intensive -- work of S. M. Aleksandrov ("SMA"), and " colleagues at the V. I. Vernadsky Institute of Geochemistry and`Analytical Chemistry, Russian (formerly U.S.S.R.) Academy of Sciences, Moscow, as weA as associates with affiliations elsewhere. According to Aleksandrov (2007, p. 153), ".....Korzhinskii (1955] regarded bimetasomatic and contact-metasomatic magnesian skarns as an individual petrochemical association, which.: is genetically related to the replacement of dolomites and magnesae, as was ,proved at .numerous deposits in Russia, China, and other countries". .Using this concept, and other fundamental knowledge, as a point of departure, this research .has made important contributions to the understanding of this aspect of geological .science.. As well as significant. additions to the recognition, definition, and development of related mineral deposits.. Including cooperative research on some localities in the Whitehorse .Copper Belt, Yukon Territory, Canada. As discussed in Aleksandrov (2007). The "REFERENCES" section of the present report affords access to further particulars of much of this work, and related matters. Featuring Aleksandrov's definitive monograph on the subject (1998), .and his recent (2007) paper. The first. author had the privilege of working with Dr. Aleksandrov, while serving as his professional host in Alaska on his .two "scientific/cultural exchange. program" visits to the U.S.A. (1973, 1979), These visits were made possible, jointly, by the Academies of Sciences of the U.S.S.R. and of the U.S.A. Thus began a collegial relationship which has continued since 1973 to the present time. Working together in the field (Seward .Peninsula and elsewhere in Alaska), laboratory. and office- proved most informative, and quite valuable. Hence the subsequent initiation of the USBM project in 1980. 2 ~M~ a~~A ~~P~~T 3 4 $. Page 4/127 in 1980 knowlege` and/or appreciation of the significance. of the work on contact metamorphic/ metasomatic "skarns" -- .especially. "magnesian skarns" -- and related. mineralization/ore deposits by SMA and hds associates was not notably widespread elsewhere. -Thus, implications of ,:~ this work with regard to understanding of the formation of skarns and related contact metamorphic/metasomatic mineral deposits,. as well as associated subsequent derivative types of deposits, were not widely appreciated outside the U.5.S.R., .and .other places where geologists from the U.S.S.R. had worked. Thus it was felt appropriate to pursue further the .possibilities of this. approach. to skarns and skarn-related mineralization/ore deposits, Especially in geographic areas where this had not .yet been done, or at least not. done to any appreciable extent. Rlaska certainly being one such area, and of course also the principal concern of the Alaska Field Operations Center, USBM. While the presence of known "skarn-type" ore deposits, featuring relatively.. well-exposed geology, existing nearby In adjacent, Canada (Yukon Territory, and Northwest Territories, in particular) afforded excellent .opportunities for the "investigative" ype of studies felt to be a requisite initial step in an envisioned research program. This latter to consist of delving. into.' the implications, .ramifications, realdtdes, value, "usefulness" of this (for want of a simpler yet informative term) "SMA approach/model" of skarn formation, etc. Fallowing the well-known mineral resources exploration philosophy. of "going to elephant country df one wishes. to find elephants", the "skarns" and associated mineralization of the Whitehorse area, Yukon Territory seemed a good, as wel! as convenient, place to start: The Whitehorse Copper Bedt and many of its localities were known to TCM from previous "visitation/information gathering"-type activities in that area while. GeologistfSupervisor for Mineral Analysis and Research with the Alaska Geological Survey, t97©-1974. These activities having taken place both before, and soon after, having met and worked with Aleksandrov in Alaska in 1973. With some decided "alterations" in professions! perspectives and appreciations having resulted from the experiences with, and knowledge gained from having fad the .opportunity to work collegially with this outstanding scientist. Visits in 1970, facilitated by the staff of New Imperial Mines Limited,. featured time, and some sample coNecting, at Little Chief, Arctic Chief, Best Chance, and War Eagle. Similar- visits in 1973, now under the aegis of Whitehorse Copper Mines Limited, included these .localities, as -weld as underground at the Little Chief. Thanks to the interest, generosity, hospitality of the knowledgeable fiosts on these occasions, the experiences were informative .and fruitful. Providing much. in .the way. of substantive "real world grist" for pondering upon. At the time, too; it was stimulating for an Alaskan geologist to experience this sort of activity in this part of Canada, given the relative dearth of such across the border. Opportunities to see, learn. As .graciously afforded do good-spirited and open .fashion by knowledgeable and interested .individuals: It is a pleasure to be able to acknowledge ahem. all -- .you know who you are --, collectively, here. As weld as express appreciation. {Writing this portion of thds report mostly from memory in the .year 2007, it is, hopefully, ample testimony to add of those Whitehorse area folks whohave been so cooperaYlve over the ears that. l have man e r y ag d to ecapture as much m the way of memories as !have. Or chose to return for yet "another round" an the Copper Belt do 2004. j 3 GMC DATA REPORT 3 4 ~8 Pa a ~5 127 9 / Some years. later, in -1980 the authors visited the then-still-reasonably-accessible, as well as exposed, known. deposits or occurrences along .the trend of this. "belt". From the War Eagle at the. north, to the Cowley Park area at the southern part. Access being provided accomodatingly by the fine folks at Whitehorse Copper Mines once again, Though names. and faces had changed some in the interim. While more than a few "field" features had .undergone ..some changes too. This work consisted of general reconnaissance, and limited.."character" sampling. at each site. Featured was another tour underground at the Little Chief.. While attempting to decide. upon "THE" site for our proposed initial detailed investigation. Features characteristic of "magnesian skarn" {per the usage of SMA) were noted in .several of the localities visited. Principal among these of course being the presence of appreciable proportions of constituent magnesium-rich minerals. Especially such as forsterite, diopside, spinet, serpentine, phlogopite, humite/clinohumite, talc, Mg-chlorite, periclase, bructte, Mg-bearing borates. As welt. as other key features of the lithologies present (textures, structures, overall compositions; "Iterations"). And the geological relationships; the "zonality"; the "positions" -- geochemicalty, lithotogtcatty, spatially,. temporally. These as ects are discussed further, in some detail, elsewhere in the course of this report. P By our criteria, "magnesian skarn" did in fact appear to be in evidence at Arctic Chief, and Little Chief, in particular.. "Likely" at Black Cub South (?). While perhaps (?) present, at least in places/to some degree, at Valerie, Best Chance, the Grafter area. By this- time, published findings of other investigators (eg. Grabher, 1974; .Tenney, published in 1981) had indicated, stated, or presented evidence supporting similar observations. Certain fundamental. aspects. of magnesian skarn, principally concerning the presence of a variety of magnesian minerals, and the "dolomitic" nature of associated host rocks, .having. been recognized.. Though appreciation of some related features, characteristics, remained somewhat vague. While other key .features such as periclase (brucite) marble, "calciphyres", "rhythmic banding" in rocks --..and in ore materials, Mg-Fe-borate minerals, had apparently escaped recognition, and/or appreciation of their significance. Though at that stage, the focus was more-compellingly on "keeping the mill fed" at Whitehorse Copper. Since, ore reserves -were "running out". A particular memory remains of some capable, knowledgeable "geo-type" individuals we had met on previous occasions. This. time chancing to meet .them, at the. southern end of the Belt, garbed in head-nets,. etc., and laden with geophysical equipment. Heading off. -- again -- into the "bush", pursuing possible: extensions of the Copper Belt_ "One more time". Concerns as to such. esoterica as the subtleties of "magnesian skarns", and so forth, not. exactly priority items just then. Quite understandably._ Adding, however, a certain aspect of "perhaps/possibly/maybe" to .our own activities. Though realizing that. the likelihood of making any contributions of positive significance, at least in timely. fashion, was probably rather small. Our .focus, of course, being somewhat different, though certainly not unrelated. So we did what we knew how to do. And wished our colleagues well As they did what they knew how to do; doing it quite well, from our perspective. One might be able to "find .ore". If ore happens to be where one happens to look. But if ore does not happen to exisf in that particular place, all the "sophisticated" knowledge accrued thus. far is unlikely to be of much help. 4 GMC DATA REPORT 3 4 8 : Page 6/127 Though. we continued to try to "add to the sum total of human knowledgen in our own: chosen "geo-speciality/sidelineA of endeavor. Since one never knows ..... As Einstein once chose to put it, "If we really knew what ii was we were doing, it would not be called research, would it?" No special effort was made at this, or subsequent stages of our work, to search 'for the: , dolomite, dolomitic limestone, or other magnesium-rich "original/precursoriaUhost" rocks - presumably requisite. as a/the principal source of the magnesium for the formation of the "magnesian skarn" minerals. It being deemed sufficient for the. purposes of our initial studies that the other criteria directly related to/evident. in the skarns/etc. ,themselves be present.. Though of course, where readily available, "apparently unmetamorphosed" (?!?) carbonate rocks were collected. Upon analysis (initially testing with. HCL; with confirmation. via. petrographic microscopy, x-ray. diffraction, x-ray emission. spectrometry) .those associated with. the Arctic Chief .and the Little Chief, in particular, included a substantial proportion proving to' be at least "dolomitic" in character. Vh/hile specimens associated. with the other , localities: were characterized by a relative paucity, to absence, of "dolomitic° .rocks (collected). This observation leading to another "observation°. Namely,. that a potentially important .aspect of the exploration for magnesian skarns and related mineral deposits ought to be ascertaining the nature of any, and all "carbonate rocks" encountered, with the view to following up especially. diligently.. on those .which prove to be appreciably "magnesian/dolomitic". Since "magnesian skarns" do of .course require some geologically. reasonable source of magnesium for their formation. While the majoroty of related magmatic materials are most commonly of °moderate/intermediate" to "low" basicity. le. "Granitics" -- granodioritic- quartz dioritic-granitic-syenitic-monzonitic-, etc. le. relatively low in magnesium content, inherently. Dioritic .materials such as may be present likely generally. reflecting. (variously)... .contaminated less basic .melt material. Though magmatic materials of "higher" basicity are known to be associated with skarns -- "magnesian" and otherwise. However these. are generally not of appreciable size, relative. to the larger ones which are more often associated with less basic (generally more "fluid-rich"; a factor in metasomatism) igneous activity. Thus it seems likely that "magnesian. skarns° of any appreciable masse presumably require appreciable magnesium from some "other than magmatic" source. The host rocks of course being the .prime .candidates: The nature of these most likely being the principal, geochemical determinant for the presence -- or absence -- of sufficient magnesium to facilitate. the formation of magnesian skarn, given the other appropriate geological conditions. As is manifest in .the literature, exemplified. by the materials in the "REFERENCES" section, and also discussed, variously, elsewhere in the present report, the presence -- or absence -- of magnesian skarn in a particular "contact metamorphic/metasomatic" geologic. environment/occurrence of skarnlike character has decided relevance in terms of the likelihood, and nature, of associated mineral deposits. .Extensive .experience worldwide: has indicated that magnesian skarns- are particularly "fertile' ground" for the formation of genetically related mineral deposits. of several kinds. Reasons for this are .related principally to the geochemistry, mineralogy; petrology (including textural features) characteristic of magnesian skarns, as well as the geologic circumstances attendant: to their formation and subsequent history/"evolution". Hence the (original) .presence of magnesian skarn (or recognizable subsequent modifications thereof) implies a reasonable 5 GMC DATA REPORT. 3 4 -8 Page .7/127 possibility, if not a distinct likelihood, that associated mineralizatian of possibly significant character might be anticipated to be present in those environs as well. ~ (n1980 .thee Arctic Chief locality seemed to afford the best opportunities to carry out the proposed initia{ investigation.. Accessibility, exposures, available information; cooperation: of property owners were .principal determining factors. While initial impressions of iithologies; mineralization, geological relationships were rather compelling. Among .other ,reasons, this locality seeemed to display certain decided similarities to some magnesian skarns. TCM had seen elsewhere, with SMA: Fundamentally the initial principal concern of the study thus- .begun in 1980 was. with 7egard to the nature of the skarns) present.- le. whether or not this was indeed-a demonstrable example of a magnesian skarn (per the. usage of SMA) .situation/occurrence. If so, as preliminary impressions obtained by TCM and JCM -- featuring. the .nature of the rocks -- ..had suggested, of: what particular "facieslvariety"? -What. key features -- mineralogical,..petrological; geachemical, geological -- did this locality. manifest? What relationships were recognizable/present? What implications might. this have with: regard to mineralization at the Arctic, Chief ore deposit? Ta other -- known, as well as, perhaps{?); otherwise -- deposits/localitiesloccurrences of mineralization in the Whitehorse Copper Belt? The neighboring area? And perhaps regionally, as well? Including .Alaska, of course.. While certainly not excluding "elsewhere"; either........ These considerations were addressed in -- though not restricted to -- the context of the concepts (featuring an emphasis on metasomatic aspects) which had been developed as the result of the work of SMA and associates. Featuring. extensive and effective applications elsewhere in the world, in terms of mineral resources: exploration; development; production, and uses -- some rather innovative. One of the more noteworthy aspects of their work having been the elucidation of previously unrecognized types of deposits of boron, and of tin. This resulting in some ~nnovaiive exploration, production and utilization methods. Raising reasonable questions as to possible implications/applications elsewhere (cf, Mowatt, 1984; Mowatt and Jansons, 1985). On the basis of the information and insights obtained as the result of working with SMA, the skarns of the Whitehorse Copper Belt were- of obvious interest; in terms. of .the geology per se, and relationships to miners! resources, known as well as potential At the time (1980), the ..definition(s), the recognition, of "magnesian" skarns as such; the. geological significance of their presence..-- or .absence --, and implications as to related mineralization, vuere topics remaining, in general, somewhat ill-defined.. "Geo-esoterica" whose- relevance, other than "academically", was yet to be determined. At the. time (other than in the U.S.S.R., 'and a few ether places) this aspect of "skarns" was not a topic of widespread apparent interest in geological science. A "skarn" was, essentially, simply a skarn..... A term meaning various things, to various people. And .more often than not, the "meanings" seemed rather. vague. [As an aside, the following remarks seem not inappropriate here: To a certain extent, with some notable exceptions {prominent among which was recognition by-other investigators {eg. Grabher, 1974; Morrison, 1981; Tenney, 1981; Watson, ..1984; Meinert, 1986} of "magnesian skarn" as such, in the .Whitehorse Copper Belt), in"many respects this state of affairs regarding "skarns° appeared not to have changed all that substantially .between 1980 and 2fl04, as it turnE;d out. Though by 2004, the technical literature (and TCM's personal library; thanks to SMA) contained even more numerous 6 GMC DATA REPORT 3 4 8: Page s/127 contributions on the subject by SMA, and associates,..including books. Cf. the REFERENCES section of this report; especially Aleksandrov, 1998; and, now,. 2007. The 1998 reference is "the book" the definitive treatise on the subject: "Geochemis t of ry i` r F rmation in D mi Ska n and Ore o olo tes . The 2007 paper (Aleksandrov, S. M., 2007, "Gold Behavior during Endogenic and Supergene Alterations of Sulfides in Magnesian Skarns"; .Geochemistry Internatiorial, v. 45, no. 2, pp. 1.52-169, Pleiades Publishing Ltd. {S,pringer}), though with a broader theme, offers a concise yet informative summary of the approach/"models espoused by Aleksandrov. As well, this paper features the. initial publication, :and discussion, of the results of our work on the Arctic Chief, by way of an example. In the context of athought-provoking presentation of the subject given in the title.. With clear implications as to .the matter of magnesian Skarns, their significance, "fertile. ground" aspect, .etc.] STUDIES: initially, field investigation and sampling of bedrock outcrop/pit .wall exposures, .associated "rubble-crop", and .related "float" materials .were carried out by TCM and .JCM at .the. Arctic Chief locality in 1980-1981. This was done in the context of consideration of various key features, and relationships, of minerals and rack types, and their "position" (geological, geochemical, temporal and/or spatial) as developed. and elucidated by SMA et al. This study was carried out by two experienced geologists, equipped with knowledge of, familiarity with, appreciation -and consideration. of this "SMA models. However, following the "keeping of an open mind" philosophy inculcated by various mentors and colleagues overthe .years, it was recognized as "only" a model..The "method. of multiple working hypotheses" t, remaining a paramount concern.. Striving at all times for .that al{-too elusive.. spectre termed "objectivity". Rea{izing that our backgrounds since having become familiair with "the SMA model", and also having experienced its apparent applicabilty/value/utility elsewhere. via first hand experience, .had in al! likelihood .resulted in at least a certain "predilection", if not exactly a distinct bias: Hence the approach adopted was relatively straightforward.. The principle concern .was to endeavor to "a{low the rocks, the geology, to speak for themselves", as it were. Though admittedly we had the perspective, advantage, of appreciable familiarity with a certain.. "dialect" of the .language, per. Aleksandrov's work, and knowledge gained by association with him. Thus of course it was rather satisfying to recognize that our own findings, during the course. of this study, strongly supported the relevance/appropriateness -of the "SMA model"_ At aeast with respect to the Arctic Chief locality. In a word, it "fit". It "worked"., According to what the rocks; the geology, appeared to demonstrate themselves. Subsequent analyses of samples ("many") were carried- out at TCM's laboratory at the Alaska Field. Operations Center, USBM, facility in Douglas (Juneau), Alaska.. Analytical capabilities featured stereo-..and petrographic microscopy (transmitted. and reflected light), x-ray diffractian ("XD"), x-ray. emission (fluorescence) spectrometry ("XRF"), and fire-assay. (ltseems relevant tv note .that toward the end of the 1981 field season, TCM and JCM visited the "Cantung" mine in the .Northwest Territories, just east of the border. with the Yukon Territory. Serendipitously, the.Mine Superintendent happened to be a former acquaintance of SMA and TCM from their 1973 work on the Seward Peninsula, in the Lost River region. 7 GMC DATA REPORT. 3.4-8 Page 9/127 W: Fotheringham, Mining Engineer,-having been in charge. of work being -done evaluating the. tin deposits. at the Lost River mine and. environs in 1973. As well. as proving an excellent, .amiable,. knowledgeable. and informative host at that time: Bill,, once again the good host, and well-remembering Aleksandrov .arid. our work together in 1973, provided a memorable and enlightening underground tour of this impressive operation. The two fortunate guests seeing, learning much. A most informative .experience. Providing appreciable food for thought. Affording valuable perspective. Also facilitating some "high- grading" of specimens of Likely interest.. "Skarns" being..:... "skarnsH (?!}.] COMMEPfTS OF! RESULTS .FROM THE 1980-1982 STU®Y: Gleaned, insofar as feasible, from an. incomplete collection of various items exhumed in 2004 from personal .materials long-stored-away.. (See remarks below regarding the regrettable "affair of the missinglfost report".) Featuring battered and tattered copies. (TCM, JCM) of .aged field notes, sketch maps, "rough-drafts", the odd scrap of paper resurrected. from an old book, etc.; also some .long-retained "paperweight"-type pieces of "choice' .specimens, other sundry oddiments. Supplemented by thoughts recaptured, variously, from personal memory. Perhaps first and foremost, the matter of the exposures of those splendid. white-lighf grey. rocks at the Arctic Chief. Gleaming and sparkling -- "basking°? -- in the-Yukon summer sunshine. Eye-catching, .even from afar: Essentially unforgettable. Well-nigh irresistible to a -field geologist. Beautiful .rocks, these. In a variety of ways, actually. "Marble(s)", apparently. Indeed, as it turned out on closer .examination. In fact the not- unanticipated "periclase (brucite) marble". This of course a key to the "magnesian-skarn" ( character of these rocks --; to the ("hypabyssal periclase facies") type of magnesian skarn so-represented; to the nature of this locality/occurrence/deposit. Pere SMA: publications, personal communications, .and remarks quoted ,elsewhere in the present report;.. as welt as now, discussion in his 20Ct7 paper; as well as our experiences together in the field. The formation of -the mineral periclase in these rocks. is of course an aspect of decided petrogenetic significance (cf: Turner,. 1968; Winkler, 1979; Aleksandrov, 1998. Among. .numerous others; over the years.:..... ). While the brucite-after-periclase relationship similarly is an important key to events subsequent to the .formation of the periclase, during the further .course. of the evolution" of a/this magnesian skarn locality. For details of this, see Alexandrov, .1998, 2007, as examples, among others, from his publications. An additional significant nuance .regarding .the physico-chemical conditions indicated by the formation of periclase in dolomitic host rocks during contact metasomatism .was stressed by Aleksandrov, in a letter to TCM, November 15, 2004: "I see in Russian translated the book Helmut G. F. Winkler who ive T cr staltiz ed g y gabbro .magma as 12000; syenitic = .9000 and .800-7000. far granitic, that. are similar with data F, G. Smith. From Winkler's data. T host rocks is .1500. (?) only. The rvzetasomatic process of alteration of dotoenite started in Kato intrtasian under action magrtiatic Si .and At-bearing solution and give primitiese skarn zonaltty as first stage process (300-4000), but not 1504:). The reaction CaMg[CO3}2 ---> MgO + CaCO3 + CO2 is 600-?--C/1Km depths. (see fig. 1, 14, 19 and 32 in my book)" . [Emphasis by TCM] 8 GMC DATA REPORT 3 4 $ Page_lo/127 Qur initial recognition at the Arctic Chief was based upon hand-fens, +/- .acid-bottle; specimen examination in the field. "Marbles", comprised predominantly of calcite; associated with appreciable. proportions of "brucite pseudomorphing/replacing periclase". This latter feature often rather `evident, even with the unaided- (though of course somewhat gknowledgeable") eye; especially obvious on weathered :surfaces of some of the rocks. While "letting the rocks speak. for. themselves". Rather apparent,. in this case, if` one happens to be "attuned to their language". Is .fortunate enough. to be properly equipped to recognize, interpret, -the features fairly clearly displayed. And. strives to "keep an open mind". Bringing certain recollections (TCM) of :1973, working' in the field on the .western .Seward Peninsula, Alaska. Quoting Dr. Aleksandrov, on one particularly memorable occasion: ` (("!s periclase marmor. If you want to see. periclase marmor, here it is. If you do not want to see periclase marmor. Weil......... But, is periclase marmor." - While displaying a chunk of light grey rock, with a certain. knowledgeable flourish. Since Aleksandrov was, after all, my guest, 1 .elected. to at least look. See. Possibly even' learn (?!). Whi)e our "otherwise-pre-programmed as to skarns", as well as somewhat "politicized", colleague of that day shrugged ~ skeptically and wandered off.)) ~ Memories of that toregaing double-bracketed bit- of {somewhat short-sighted) "geo(political)-byplay" remaining with me ever since. From a personal. first-hand introduction -= education -- provided, in 1973, on an upper flank of Brooks Mountain, in the Lost River region. Followed, some years later, by recognition of similar features, in the field at the Arctic Chief. Duly followed by laboratory confirmation under the microscope(s). Further confirmed dia x-ray .diffraction. and x-ray emission (fluorescdnce) analyses. of numerous specimens. Interesting rocks, these. With much information to offer. If afforded-the. opportunity to "speak .for themselves". Mineralogy recognized featuring calcite, +/- dolomite; .brucite (pseudomorphous after periclase; not. infrequently with associated relict periclase present as well);. -minor/trace amounts (varying among specimens) of spines, forsterite, magnetite, phlogopite, serpentine, ; tale, "hydrotalcite", amphibole, pyroxene, (+/- ?). The "carbonates" featuring crystalline "marble-like" textures, with traces of variously-.well-developed/-vague, not infrequently "patchy", mineral- and textural banding in places. Many truly exemplary -- "classic/textbook" -- examples of periclase (brucite} marbles were examined in specimens collected from this7ocality. (As Weil as in some "characteNgrab samples" from several sites elsewhere in the Copper Belt). As SMA was to observe, -even. more years later (2005), the Arctic Chief indeed. features. "splendid" periclase (brucite) marbles. Hitherto unrecognized by other investigators., to our knowledge. If recognized,. not .reported, to our: knowledge. If the tatter is actually the case, ane might. speculate as to, perhaps, the degree of appreciation regarding the fundamental petrogenetic/geochemicat significance of the formation of the minera! periclase, as well as its subsequent replacement by brucite, in these -- or any -- rocks. Not to mention. the relevance to mineral deposits. 9 GMC DATA REPORT 3.4..8: Page 11/127 This .apparently "initiaC recognition" -- with subsequent full confirmation by SMA in the course of our 2004-2007 study -- of periclase.. (brucite) marble at the Arctic Chief (west) suggests .that .perhaps further reinvestigation/reconsideration is merited of these,. as well as associated rocks, "skarns", and mineralization in the area, the region, and elsewhere. As also indicated by our (1980) recognition, and confirmation (via petrography, x-ray diffraction), of a number of examples of periclase (brucitey marbles in the "character/grab samples" mentioned above, ,.from sites at both the Little Chief and Black Cub South localities.. Such periclase (+/- brucite) marbles -- and associated/related. materials -- perhaps (likely} {urking, as-yet-unrecognized/undetectedl(unsought), ..elsewhere, in this, and. other, regions. With attendant. implications, scientific and "otherwise", regarding any. such yet-to. be-recognized occurrences. Among which implications,"practically speaking", recognition -- distinction as such. -- of periclase (+/- brucite) marbles (and/or dolomite/"dolomitic" carbonate rocks as well): perhaps representing a potentially useful "exploration guide/tool". The presence of dolomite/dolomitic carbonate rocks in a particular. area affords at least the geological/geochemical possibility of magnesian -skarn in the vicinity. While the presence of periclase. (brucite) marble strongly .indicates, if not essentially assures, it. The. tatter indicative of metasomatism/metamorphism of appropriate .character, sufficient to have resulted in magnesian skarn formation from precursorial dolomite/dolomitic carbonate rocks.. Such periclase (brucite} marble .characteristically representing the "outer .zone of the contact aureole" (Aleksandrov, 2007) of such. skarn. Definitive of the "hypabyssal periclase facies" of magnesian skarn, per SMA et al. Should, additionally, rocks of "calciphyre" .character also be recognized, this would afford further .information as to the likely "whereabouts" of any: associated "mineralization"/ore ( deposition. "Clues" as to "where to look next" in the vicinity,. surface and subsurface. As related to the matters of "zonaiity", "positions", as manifested in/by magnesian skarns. As discussed elsewhere. in the present report. In addition to these "splendid" marbles, there were also other. variations on the theme-of "carbonate" rocks to be found at the Arctic Chief. Those somewhat "marble-like" rocks we termed "calciphyres" in the field. Confirmed as such in the laboratory: In addition to predominant calcite (+/- some dolomite}, characterization of other minerals -- microscopically, supplemented by XD and XRF -- in these specimens revealed, variously, forsterite, pyroxene, spinet, .serpentine, phlogopite, chlorite, ciinohumite (?), .amphibole, magnetite; +/- talc, magnesite. -With relationships,. textures characteristic of "calciphyres". Banding, of (varying) "rhythmic" character, likely attesting to metasomatic activity of non-equilibrium character, manifested. All of these .factors indicative of the "magnesian skarn" nature of .this locality. As well as consistent with the concepts developed by SMA.and colleagues. As the rocks continued to "speak for themselves": Though in a certain particular.. "dialect", apparently. Also recognized was similar ("rhythmic") banding in "ore" specimens. Featuring in these materials magnetite, +/- .sulphides, (+!-?); these alternating .with associated "bands"!"foyers" of, variously among samples, forsterite, serpentine, phlogopite, clinohumite(?}, amphibole, +/-?. Further attesting to .the "magnesian skarn" character of this deposit. As well as presenting significant. evidence as to the genesis of these "ores". A key ~ feature. Per the SMA "model". 10 GMC DATA REPORT 3 4 ~~ _ Page 12/127 These characteristics interpreted as indicative of/evidence for metasomatic replacement of pre-existing ("banded") calciphyres. The carbonate portions of the precursorial rocks having been. preferentially replaced -- predominantly/completely -- by magnetite, initially. (The sulphides now. present in the. ores having been deposited later, as "overprinting" during subsequent/continuing "postmagmatic"/"retrograde" metasomatism.) While the silicates such as forsterite, etc.,. originally present in the calciphyres were .partially/completely. altered to other magnesian. silicate minerals, such as serpentine, phlogopite, clinohumite, +/. i h i in I rh hmic bandin remainin as "relict structure" haven been W th t o or g a yt gy g "inherited", and now manifest as repeatedly alternating bands of ore minerals. and bands of silicates. The mineralogies having changed, while evidence of metasomatic replacement remains in the form of the "relict structure" of the rhythmic banding, as well as by the continued silicate mineral character of the "non-ore" bands-in the "newer" rocks. Also.. present (though admittedly recognized, eventually, principally because we searched most diligently, hoping to find them), in some marbles and calciphyres collected in this initial study, were some. rather small. "needle-like/-shaped" black crystals..Suggestive of, possibly, a member of the Mg-Fe-borate mineral series "ludwigite-vonsenite"(?). Such morphology being a characteristic feature of ludwigite (cf. Ramdohr; lJytenbogaardt and Burke; Aleksandrov). Ludwigite being a mineral characteristically occurring in magnesian skarns. In our specimens, these crystals unfortunately too few for definitive XD analysis. X-ray emission (fluorescence) spectrometry of bulk sample and partial-concentrate materials (the samples. proving not readily amenable to sufficiently effective concentration of enough of these small- "needles" -- even though magnetic -- for meaningful XD or XRF analysis) indicated relatively high.. iron contents. Suggesting that the black mineral. could. be magnetite. Apparently corroborated by the magnetic character of some few of these .grains obtained, recognizably, as "separates", after .appreciable effort. And of course magnetite is not uncommon -- rather characteristic, actually -- as a pseudomorphic replacement of Mg-Fe-borates. As indicated in the literature by Ramdohr, Uytenbogaardt and Burke; .Aleksandrov. All affording, at the time, the (quite) speculate+re possibility .(subsequently... confirmed, in another specimen, by Aleksandrov [2007]) of original needle-shaped crystals of Mg/Fe- borate having formed as a mineral of the "ludwigite-vonsenite" series in these rocks. This recent confirmation providing additional evidence supportive of the magnesian skarn nature of the Arctic Chief locality. As well as providing .further insight. into :other petrogenetic and geochemical particulars of its character. The geochemistry .and mineralogy -- as well as ,mineral/ore deposits -- of the element boron being another .aspect of magnesian skarns having been studied, extensively and intensively, by SMA and, associates over the years. During the 1.980-1982 study, it appeared that similarities of the Arctic Chief to the .Brooks Mountain Tin Creek, etc. localities in the Lost River' re ion western Seward.. Peninsula, 9 Alaska) were rather .intriguing. This impression enhanced by samples and photographs. from otherlocalities furnished by SMA during the course of our ongoing association since 1973. As well. as confirmed in a letter from him in 2005 (quoted elsewhere in the present report), during the course of his .subsequent study of materials from the Arctic Chief Iocaliiy. (As Dr. Aleksandrov once observed wryly, though with his usualsense-of-humor, in a somewhat different, though not totally unrelated context, after watching a rock specimen break.... I'~ the "wrong way" under his hammer in Alaska: "Every country ----, same result".......... ) 1 1" GMC DATA REPORT 3 4 ~8~ ~ Page '13/iv Thus, in summary: The "rhythmic-banding".......... in rocks, and in ores.. The mineralogies........ The plethora. of mineralogic, petrologic, geochemical indications as to the apparent "magnesian skarn" character of the Arctic Chief........ As gleaned from the "collected works", on-going correspondence, and first-hand personal .experiences working with SMA....... As manifested in the rocks of the Arctic Chief locality... Further including, as a matter of "position" (geologically; spatially, as observed in the field), the apparent relationships (displayed at various scales, .from hand specimen. up to deposit dimensions) of: igneous rocks, ..generally of granodioritic-quartz dioritic-dioritic character; "(calcic-)skarn" materials --- pyroxene, garnet, +/- ; relative to the principal "ore" occurrences of magnetite and other- ore-minerals; -the (generally) more "distal" calciphyres; .relative to the further-distally-positioned periclase (brucite) marbles; .these .constituting the "outer zone of the contact aureole°. Manifesting the sequence of geochemical evenFS, petrological processes, .and geological relationships recognized and elucidated by SMA and co-workers; the- "position(s} ; and .the "processes" attendant thereto. An initial lesson from Dr. Aleksandrov in the field in 1973 was that "tt is a matter of position". Easily remembered, but. less readily deciphered; let alone "mastered°. Though certainly well worth the effort, as it turned out: Professionally as well as personally, .over the years: As our initial study at the Arctic Chief showed, "it fit; it worked; it made. sense". -Sort of an "order out of chaos" experience for the first author, over the years, with. regard to "skarns". At least a "relative" degree of order; appreciation; .comprehension; .understanding. Recapitulation of the "evidence": Periclase (brucite) .marbles. Calciphyres, with predominant calcite (+/- dolomite); as well as, variously, forsterite, .:.pyroxene, clinohumite (?), magnetite, chlorite, phlogopite, serpentine, spinet, +/-. Pseudomorphs ("possibly?", at the time of the earlier study) of magnetite- after "boraces"; later (2007) confirmed by Aleksandrov to be Mg-ludwigite . Ores of magnetite, forsterite/serpentine/phlogopite, +/- sulphides. Rhythmic banding in rocks, and in ores. "Zonalityn; "position"; artd -the character thereof. Spatially, geologically and geochemically. Exhibited at various scales. Relationships (and nature} of successive "magmatic" ---> "posimagmatic" events/minerals/etc.: (le. "prograde", and "retrograde", respectively.) Representing "recognition", by the criteria used by us _in 1980-1982, of the Arctic Chief locality. as a "magnesian skarn" occurrence/-related. deposit. With attendant implications as to geological, petrological, geochemical, and mineral resources considerations. The principal geochemical determinant for the sufficiency, or paucity, of the required magnesium for magnesian skarn formation being the nature of the "precursorial" host rocks intrutled by -the related igneous material(s). As now manifested, in particular, by the geochemical, mineralogical,- petrological character of the °outer zone of the contact aureole" at the Arctic Chief deposit (and, evidently, at least portions of the Little Chief and the Black Cub South localities as well). 12 6MC DATA REPORT 3- 4 ~ Fage 14/127 Namely, those. "splendid" periclase (brucite) marbles, derived from dolomite/dolomitic host .rocks; under conditions of the "hypabyssal periclase facies" of "contact-metasomatic magnesian skarn" formation. Manifested similarly, and. complemented by, the nature of the other rocks, .relationships, in evidence as well. These. rocks merely. "speaking for themselves°. Though with a certain decided eloquence. Per "standard procedures" in the agency, a U: S. Bureau of Mines "Open-File Report" was prepared dealing with the .results of thisi 980-82 work: The "final-draft" of this report (cf. Mowatt and Mowatt,1982); together with fifes, rock and .mineral samples, petrographic specimens, and related analytical data, were left with the Juneau office of the Alaska Field .Operations. Center, upon TCM's resignation from ahe USBM in mid-1982. Unfortunately this report, as well as .the related sample materials, files, and analytical data, subsequently. "were Iostlwent missing"..Not -- heretofore -- "standard procedure" (?), Likely similarly disappearing completely, upon abolishment of the U. S. Bureau of Mines by the U. S. Congress, ca. 1995.. "Geopolitics"...... in one guise or another(?). However, "science marches on"....... As the, saying goes. Some people being "obstinate". CONTINUING STUDIES:. Results from the ongoing work by SMA and colleagues continued to appear trr the technical Literature. Summarized, in particular, by the publication of Aleksandrov's comprehensive book "Geochemistry of Skarn and Ore Formation in Dolomites". initially appearing in 1990; in aRussian-language. version; an updated version was published, in English, in 1998. This .monograph (the "(SMA; 1998]" .book) providing a valuable, as well as timely, integration and summarization by an increasingly well-known, respected investigator. An acknowledged authority, with extensive experience (of fundamental research, as well as "applied", nature) with this complex subject. The breadth as well as depth of the work of Dr. Aleksandrov and his. colleagues most impressive; and seemingly ever-expanding in scope.. It was a privilege to retain our relationship. A continuing education; an ongotng "post-doc". In combination with continuing correspondence, exchange of books,. papers,. data, samples; photos, .ideas, etc. with. SMA over the intervening years, the- "synthesis" afforded by this particular book spurred TCM to revisit the Arctic Chief locality in 2004, upon retirement and relocation to :Haines, Alaska. Though admittedly a certain level of fingering. professional frustration, as well as personal "annoyance", rE:garding the unfortunate "disappearance" of the previous efforts of 1980-1982 might well have provided an additional motivating factor. Scientists generally dislike losing "hard-won data"; among other fundamental concerns. Further strong incentive was. the opportunity. afforded to work with Aleksandrov once again. Though this time, "across-the-miles". Providing him information, samples, literature, etc.. from yet .another locality; to add to the many others he'd already studied. As well, adding to the first author's knowledge.The subsequent work in Canada and the USA was "unfunded"; carried out at the personal expense of TCM. Sort of an ad hoc "post-doc"; as it were; though a rather "low budget" one. As well as an acknowledgement, atestimony, a "professional courtesy", as it were, to a valued colleague -- and mentor; ,friend -- of Jongstanding. 13 GMC DATA REPORT 3 4 ~8 . Page i5/i2~ '~_ With the view to rexamining this "mined-out" ore deposit, in hopes of confirming -- or improving upon -- the information ,obtained in our earlier "lost" study. Fie{d sampling was done =- again -- by TCM during the. summers of 2004-2006. The "retired" field geologist/ "sampler" ..for this project reaching the age of seventy. in 2006 (?!). Now.. truly a "mature°, as well as experienced geologist. Though perhaps na longer quite as agile -- nor nearly as well-funded -- as in days.. of yore. But "motivated". As before, samples of bedrock (outcrop/pit walls), as well as associated "rubble-crop" and. related "float" materals-were obtained. Taken, insofar as feasible, from the same general ; areas of the Arctic Chief as had been sampled during the previous work. While working. principally from memory in this regard. While emphasizing the "west" pit this time, for reasons of economy, efficiency, while seeking optimum "representative" sampling of the spectrum.. of materials, and relationships,. "positions' ; afforded at this .fine locality. A substantial collection -- rocks; related field information, photographs -- resulted.: All of the "many" samples collected were subsequently examined further,. in preliminary fashion (essentially- "triaged", as it were),. by TCM in Haines. Utilizing hammer,. chisel, hand lens, acid bottle, and a 30x/60x stereo microscope on rock surfaces (freshly-broken and otherwise). In someselect cases, also examining grains-in-oil :materials using a personalty- owned petrographic microscope. Deferring to SMA --.the acknowledged authority -- for decisions as to thin-/polished-section petrographic analysis, etc., as he saw fit The "low- budget" .circumstances of the. "project" essentially precluding petrographic-section....: preparation and analysis by TCM, inany case. Selected "triaged° materials. (some one hundred-plus specimens,. in alq were then mailed to S. M. Aleksandrov, at the V. I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, for examination, evaluation, and further analysis as he deemed appropriate to his own. ongoing research. This latter work included hand specimen, petrographic microscope, ...microprobe analysis, etc., of representative materials of particular interest. As well. as .his astute observations, insightful comments, definitive interpretations. Following sections of this present report deal with results of these examinations, .evaluations, analyses; summaries, comments and interpretations. (While Part 2 of this report, the "Data Supplement°, .presents additional. information: sketch maps showing general locations of sample sites, abstracted field notes, results of 30x/60x stereo-microscope examination of samples, petrographic microscope examination. of selected materials as grains-in-oil, and other comments, :principally by .TCM.) COMMENTS (TCM) REGARDING THE PAPER. "Gold Behavior during Endogenic and Supergene Alterations of Sulfides in Magnesian Skarns" BY S. M. ALEKSANDROV, PUBLISHED IN GEOCHEMISTRY INTERNATIONAL, 2007, VOLUME 45, No. 2, pp. .152-169: In the context of the present report, first and foremost among comments which might be put forward is that, in portions of Aleksandrov's paper, the results of our work, ,variously, on the Arctic Chief locality over the years are nicely summarized, and utilized. Representing the initial publication of any of this information in .the open literature. 14 GMC DATA REPORT. 3 4 8~ : Fage. 16/127 In addition to :material from other cited sources, his., paper uses the results of our investigations to present the Arctic Chief as one of several mineral deposits selected to exemplify aspects of the broader concerns discussed. The known occurrence of valleriite at this and other nearby deposits is particularly relevaiii, given the rote of such: hydroxisulfide minerals in several aspects of the geochemistry of gold (as well as platinum-group elements),. as discussed in this significant paper. As evident. from its .title, this paper overall is of a more general nature. Quoting. from .the informative Abstract, "The paper presents materials on the genesis of gold deposits of the magnesian-Skarn association......: The materials presented in the paper characterize the behavior: of gold in the endogenic and supergene processes at magnesian skarn deposits.n In addition,. as essential background information antecedent to dealing with its principal topic, the "introduction", and the immediately following: "Genesis and Zoning of Magnesian. Skarns", sections of the paper, pages 152-153, offer a valuable and concise summary of magnesian- skarn per se, from the viewpoint of a recognized authority. on the subject. !n the "Introduction", in the first two paragraphs, besides commenting on the mineral resources aspects of magnesian-skarns, also offering same other rather cogent observations in the process. Observations which, from personal experience, seem quite appropriate. Since they concern themselves with matters of fundamental significance to geological science.- In pursuit of increased "sophistication, efficiency", etc., as scientists we continually need. to remind ourselves not to do disservice to the "basics" in the. process. Lest,. among other things,. we fail to "let the rocks speak for themselves", as it were. A fundamental tenet of geological science perhaps at times followed somewhat less conscientiously than. might be desirable. ( The "Genesis and Zoning. of Magnesian Skarns" section offers a veritable tour-de-force in one page, nicely summarizing the accrued knowledge, experience, and perspective of many years, many localities/deposits, many rocks, and much thought on a complex subject. Leading into the following section by ending as follows: ".Sulfide ores, including those-.with gold, in hypabyssal skarns are eery diverse and are deposited during. the postmagmatic stage, selectively replacing compositionally diverse metasamatic zones of the contact. aureoles. TP~is can be illustrated` by the example of the Arctic Chief Cu-Au deposit, Yukon Territory, Canada........" -The next. section; "Arctic Chief Skarns and Ore Mineralization", pages 153-156, then proceeds to develop this theme, utilizing information obtained from other sources, principally Tenney (1981}, and Meinert (1986), as well as the results of-our own studies. Among others, one important point in particular seems worthy of special note here in this commentary. On his page154, Aleksandrov observes: "The magnesian skarns of the Arctic Chief deposit occur not only at contacts. with the (main] intrusion but also around. injections of diorite melts into dolomites (Fig. 2}. The rocks preserve their zoning. and inclusions of Mg- ludwigite in the forsterite calciphyres but contain no magnetite ors mineralization" [associated directly with the. latter,. smaller/minor `injections', ie.]. 111ustrative of this; his Figure. 2; on page 156,, offers a fine drawing of a rock specimen.. This specimen happens to be the one designated "TM-04-10-12-22-B-104" when it was ~ collected in the field at the Arctic Chief on Octoberl2, 2004, at sampling locale "22-B". 15 GMC DATA REPORT 3 ~{ 8 Page 17/127 Described (TCM); upon recagnizing, then collecting, .this particular specimen in the field: "Ah yes.. He (SMA) ought to like this one." Subsequently, in his "triage'' phase of analysis terming. it a °VERY N1CE SPECiMENn, among other comments (cf. Part.2 of the present report).-:This specimen was subsequently sent in its. entirety to Aleksandrov. Studied, depicted .and .discussed by him. Who also apparently found it a `nice-enough', if not indeed a "very. nice specimen". Collected in the near vicinity of a larger skarn/apophysis/lens of tongue-like aspect, fieatur•ing zoned igneous and "skarn" materials. within carbonate host rocks,. with green, blue, +/- "rusty"-/copper-staining .present in places along its margins. This larger feature is a rather "gaudy°/spectacular one; well-photographed, 2004 and later. Subsequently, in 2006, sampled in detail as "TM-06-8-22-2-........fl. All of which,. samples as well as selected photographs, were duly sent to Aleksandrov for his use. The :location (mentioned, -and depicted, in Heon, 2004, "Sheet 2") is at the northern edge/margin of the entrance cut of the Arctic Chief (west) pit, exposed up on the side/wall of the cut. In the vicinity of the core/crest of a tight/overturned fold in the. carbonate host rocks. Below map #3 lie. TM-04-6-9-3 locality). [Cf. maps, descriptions, etc. in Part 2 of this report, the eparate "Data Supplement".] Other comments on this specimen in earlier letters,. SMA to TCM: "Ludwigite is in serpentine-bearing marble TM-[04]-10-9 2-22-8-104... May be in contact .with marbles you can see kotoite Mg9(603}2? ......." "....... (The best you can see in TM-04-10-12-22-B-104 --- [the sequence] around. diorites' injection in marbles:. exchanged ["altered"] diorite--clinozoisite rim-- (~ pyroxene , skarn--banded ludwigite-bearing forsteritic calciphyre--banded periclase (brucite) marble.)°. According to ifs caption, this Figure. 2 illustrates "diorite injection in dolomite and zoning 'in magnesian skarns"........... Recognized as-such in the field, too. Collected with precisely this intent, .this specimen is used as an example -- "in miniature/microcosm", as it were -- ' of the general relationships ("positions", "zonality~) typical of magnesian skarns, at various. scales from. hand specimen, as here, through "deposit scale". Per the "model" for the.."geochemistry of skarn and ore formation in dolomites" as developed and set forth by Aleksandrov and his associates.."lt is all a matter of position", as the mentor here once confided to me, in the field, early on ............ Providing further. illustrative bonuses, as observed, and .depicted, this informative specimen also features "rhythmically.. banded forsterite calciphyres", and "disseminated crystals of magnesioludwigite". In addition to the other compositional and textural features characteristic of magnesian skarns so nicely displayed in this one specimen.. Collectively, "the rock speaking. for itself", as it were...... Though an appreciation, comprehension,.. understanding, of the °language" is, admittedly, important to this....... This .Figure, this specimen, the evidence afforded, .supplemented by Aleksandrov's comments, sufficiently. informative to merit. incorporation in the present report. A "key" item. Thus this ` I Figure 2 and its entire caption are reproduced below: 16 GMC DATA REPORT. 3 4 $'~ Fage ls/12~ l 56 aLEKSaNDROv . 11„1,,:11 ,~,>~ ,~,~;,//..%, ~:__ -- -~ ,~:' Zo r r - -- \,I,ILd~I,\1 ~\\\\ \\~\\\ 4~1+1,r llr \, 1 ~~ 1 n~ t'1~~~11 ~ 1~ ~\` ~` 1,,1 "'FoCa' 1'~~ `~' %D elf*r ~\\~.~\Lt\111 ~ti 11 ~~\tl~\111'~~n~f\1~~~\\ __ ~/i/ \\ \\\ \~'\\ \\\\\.\ \\\` \ \\\\ \\~ \\\\\\~~i~////~~ jl\ \`~ 111 lriaili irrrrrr/n////'Ilill\\\t'i~~~I,fia~~c'~i~~S ~',,~/,/~Iti\~\\\a l /r// 1 /71111///r/~!'il~ill(~\\-~ 111*r\~:~.\ •~~~,/ \ ~`\_=- 1 r //tirrr~rrr/'1~; \\\ 21\\\ \ 1~ ~~i'4Ci22~~ -_~ Fig_ 2. Diorite injection in dolomite and zoning in magnesian skarns. arctic Chief deposit (sample ofT.C. Mowatt). (1) Diorite replaced by zoisite (Zo); (2) phloDopite-diopside skam (Ph); (3} diopside s?carn (Di); (4) r;tythmlically banded farsteri[e calciphyre (FoCa}; (5) disseminated crystals of magnesioludwigite (Ld). Magnification 2.5x. t 1 f ~ CMCDATA REPORT 3.4 8 Page 19/127 The remainder of the Aleksandrov paper deals in some detail with the broader topic of concern, as to gold (+/-PGE), sulfides, and magnesian skarns. Providing much material. worthy of further attention. Especially :the. role of "hydroxisulfides" of the valleriite-tochilinite, etc. genre. Note. especially. p.160, comments re/ "brucitization", etc.; also similar. observations elsewhere throughout his paper. All with implications. of fundamental scientific, as well as "applied", .significance. Summarized weU in his "Conclusions" section. In terms of the aspects of magnesian skarn, petrogenesis, mineralization, etc., under- consideration in the present report,. some observations come to mind. The fundamental importance of the initial formation of magnesian. skarn. Key to the. entire sequence of subsequent events, processes, results discussed in the Aleksandrov paper. An :.example of the concept/notion of .magnesian_ skarns as "fertile .ground" for formation of associated mineral deposits. In this particular. case, the potential for the subsequent/eventual formation of hydroxisulphides such as valieriite, -.etc. Thus providing attendant further geological/geochemical possibilities. And so on........ As discussed in his paper. The pathways, geochemically, mineralogically, of :chemical elements. of principal concern, including. "precious metals" as well as essentia! other components of the required "carrier" minerals, during the sequence propounded by Aleksandrov. These being critically dependent: upon the overall magnesian skarn physico-chemical environment, during .the magmatic! prograde as welt as subsequent postmagmatic/retrograde stages of the evolution of such skarns. The "overarching" genera! mineralogical!petrological/geochemical// "PTC" .aspects of the evolution of a magnesian skarn per se are complex. Likely. subject to perturbation(s), if not outright significant change(s), during. the. course of geological events and accompanying.. ( pressure/temperature/geochemical environment(s) -- ie. the "PTC" conditions -- attendant to the formation and continued evolution of ..any given/particular magnesian skarn occurrence. While the "fates" of associated "minor/trace" elements such as gold, platinum-group. elements, key base-metals, as well as other "minor" constituents.(featuring of course sulphur, H2O/"OH", +/-) required as essential major canstituent components of sulphides- and hydroxisulfides, .are intimately connected to this evolution of the predominant geochemical components constituting the major constituents of,the "magnesian skarn" materials, as well as the overall geochemical. environment in which the skarn exists. Which latter of course varies with time, along with the evolution. of the skarn occurrence; and geological "vicissitudes". Thus the uttimate formation/behavior of discrete "micron-/sub-micron-sized" particles of precious metals, their relationship to such hydroxisulphide minera{s as may be developed, are dependent upon the previous initial formation of magnesian skarn, and subsequent. essentially ".normal" evolution of skarn and associated mineral. phases. Essentially, much, if not-indeed all, is contingent upon this......... In turn, further .growth in mass., of these "seed" particles,. possibly leading. eventually to "nugget" formation, though perhaps directly related to:.this-- in part/for some period(s) of growth/time -- eventually reaches another stage. At which dependence becomeslis, rather, princeally -- essentially entirely -- upon the subsequent .(rather than, directly, the prior) "physico-chemically"- determining course of geological events, and accompanying. geochemical responses of these "seed" particles. t8 GMC DATA REPORT 3 4 8 Page 2o/12z - -- At which juncture the direct effects of magnesian skarn-related processes and materials in this. aspect of the scenario essentially have come to an end. Merely lingering on as a "{egacy"; having served .basically. as a "template" of sorts. An essential template. Rroviding a/the key element: affording "fertile ground"; providing "opportunity/iesu. The title "Gold Behavior during Ehdogenic and Supergene. Alterations of Sulfides in Magnesian Skarns" seems particularly Weil-chosen. It conveys the essence, of the matter. This: paper offering athought-provoking treatment of a subj{sct of appreciable interest in geology! geochemistry. A subject of long-standing. interest; discussion; research; controversy. Regardless of the ultimate outcome of the pursuit of this particular concept; as presented, in terms of furthering the- understanding of "nugget" formation,, the presentation does -- at least -- indeed. serve to convey some of the "singular" aspects of magnesian skarns. Without- which singular aspects, the scenario discussed in the Aleksandrov paper would be most unlikely. Hence, again, the demonstration of one particular facet. of the "fertile ground" aspect of magnesian skarns. There are other facets, including especially those of (other) chemical, textural, temporal nature as well; the physical geochemistry involved .is complex .indeed. The .implications. these facets present by their mere existence in a magnesian skarn. geological setting, the "fertile ground" possibilities inherent, would seem to merit due consideration.- This is an important paper. As suggested previously, above, it is "thought-provoking". Stimulating. A valuable. contribution. to the technical literature. For the discussion of the chemistry/geochemistry per se, as well as other more peripheral concerns regarding geological science;. including of course mineral resources. As a bit of a digression' here, one intriguing line of thought .thus= provoked° has to do with the ( sort of "legend" that seems to develop in many mining districts. Interestingly, seemingly most commonly those in the "north country". Perhaps in this case attributable to thoselong dark cold winters "up north". Giving folks something different to .think about, tack about, if nothing else. While; on the other hand, perhaps .there just might in fact be some .other factors involved.. Such as geochemistry, "cryogenics°, etc.. (?). The genre featuring .various whisperings, mumblings; or "more substantially°(?}, rumors, stories, tales..:...... Ail having to do with the supposed, alleged, sometimes trongly avowed, "once upon a time° observation(s) of large -- or at least of unusual size -- particles of "visible" gold during the course of milling-type operations somewhere in the area. Some such "reports° featuring .alleged "nuggets" in .ores, concentrates, etc. generally otherwise, devoid of recognizable-size material of that nature. The Whitehorse area of course has by no means been immune to the growth of this sort of "legend", Nor. perhaps the growth of "nuggets" either -- per Aieksandrov, R. W. i3oyle, etc. papers -- over. the years (?), Since the recovery of "free gold" in the course of the milling process at the Little Chief site has been reported, substantiated. While details of certain other such related stories tend to vary with tine source of the information, being shared generally only ,after the recipient. has been sworn. to secrecy, Though inevitably, or so it seems, .not infrequently there appears. to be at least .some semblance of credibility to the story. A "grain of truth", as it 'were (?). Just sufficiently enticing...... Featuring. "reports" of fair-sized gold being noted, recognized (perhaps even,. at times -- perish the thought -- "short-circuited") by keen,. attentive folks in the mill Not necessarily always folks formally assigned such removal of recognized sizeable gold from the circuits. Hence of course maintaining that certain .element of surreptitiousness so vital to - ( perpetuation of any such legend worthy of the name. 19 GMC DATA REPORT 3.4 8,:` Page: 21/127 "Covert operations" of a sort, in the milt. By the keen, the alert. "Souvenir. hunters". Or merely an informal/ad hoc variation of a program of "on-the-spot .awards" for.' superior performance on .the job. In this case, presumat~ly for "attentiveness". Whatever........ (??). In light of the material presented in Aleksandrov's paper, perhaps (?) some "considered reconsideration" of tales.. of "nuggets in the skarn/at the mill", etc.. just might be merited. Since Whitehorse has been shown to Jae "valleriite country" (Petruk et al, 1970; Harada et ai, 1973; etc.). All of which would be .merely one more "interesting" aspect of the line of reasoning put forward. in Aleksandrov's rather intriguing discussion: .While of course the present author of these comments is not unqualified to raise the issue, or offer perhaps-dubious commentary. Since, among other things,. he happens to be, at least relatively speaking, a "Variag" in the Whitehorse country.. Aleksandrov once having told me about the "Variag". The "Viking"; "!he man from out-of-town with -all the answers". Seems this phenomenon is known worldwide. Be .the visitor from Ottawa or Washington,: D. C.; Moscow or Magadan. Or other points "out there"; even such unlikely spots as Haines, Alaska:,.... But, now, "end of semi-serious.- digression". Leaving the foregoing "nugget question" as a somewhat open -- "thought-provoking" -- one, in alt of its many nuances, to return now to the main thread of the present report. To our knowledge, our work, as presented in Aleksandrov's cogent discussion, .represents the first such treatment (at least published, in the open literature) of the Arctic Chief .from this particular viewpoint of the genesis of skams and related ore formation. As such, it offers a somewhat different perspective-.than apparently has heretofore been brought to bear on this subject, at this particular locality/deposit, or in the Whitehorse Copper Belt, or in the .region. This would seem to be a perspective meriting more extensive .appreciation, consideration, application than previously has been the case. Aleksandrov's .comments regarding .the Arctic Chief, based on information/data derived from the other sources mentioned above, as well as our own; .demonstrate the apparent applicability, "utility", relevance of thds "model" to this particular :locality/deposit.. As well, in the context of .this approach, and its demonstrated usefulness elsewhere, suggesting possible implications with regard to skarn and ore formation in this` region too. The "SUMMARY AND CONCLUSIONS" section of the present report, below, also offers' a bit more commentary ("grinding-of-the-axe"?) on this theme. With regard to the analytical and interpretive: details, Aleksandrov's findings confirm, are in agreement with, the results, tentative and otherwise, of our initial .work carried out in 'i980- 1982 on the Arctic Chief (see above).. Not. too. surprisingly, of course, given the. background of the professional relationships among the investigators. -The subsequent work since 2004 confirming those earlier .observations, in general, as well as in most all of the details. As well as, importantly, providing confirmation of the formation of Mg-ludwigite at the. Arctic Chief. While adding. a substantial, increase in -the level-of-confidence in the previous analyses and interpretations of two of his "students", ,with S. M. Aleksandrov as the Principal Investigator this time. Including utilization. of microprobe and other capabilities at the. V. I. Vernadsky Jnstitute of `Geochemistry and .Analytical Chemistry, Russian Academy of Sciences. Providing definitive results from our cooperative efforts. 20. GMC DATA R~f'ORT 3 4 ~~8 Page 22/127 Featuring the salient contributions of S. M. Aleksandrov, some selected observations, comments, etc. resulting from our 2004-2007. study of the Arctic Chief are presented. in the l following portion of this report. These are intended to offer additional perspective, insights, supportive- information,. some relevant details, etc., in the context of our research. The matter of the nature ("magnesian" vs. "non-magnesian") of the host rocks, and of -the associated skarns, appears to merit an additional brief comment at this point.. Various observations, over the years, in the papers cited. previously above (viz. Grabber, 1974; Tenney, 1981; Morrison,1976, 1981; Watson; 1984; Meinert, 1986; Wheeler, 1961; Kindle, ..1964; Dawson and Kirkham, 1996; Heon, 2004), have, in one fashion or another, collectively shed appreciable light on the subject. The material compiled and presented as to "majorhost. rack type", and associated "skarn minerals" in Watson nicely summarizing the data, and rather clearly showing the direct relationship, in the deposits of the Whitehorse Copper Belt, as discussed elsewhere in the present report. The Arctic Chief is certainly a fine example of a "magnesian" skarn situation. ;While the Grafter Extension, visited. by TCM per the suggestion of Mike Burke (YGS) in 2004, .affords, apparently, a relatively small but nicely displayed version of an essentially "non-magnesian" skarn situation (cf. Neon, 2004).. This latter occurrence, as presently exposed, offering a ready opportunity for further detailed study of the rocks, and .their relationships, "in miniature" as it were. Even .upon somewhat cursory field examination (TGM), a number of significant features were evident. "Granitoid" intrusives; "alteration(s)"; endoskarn; "inclusions"; -exoskarn; carbonate -host rocks, with some "interesting° features. Though some apparent "complications" -- possibly noteworthy -- were observed in this sequence as well, ( The section .immediately below presents some of the. general comments, observations, results, interpretations, etc. shared with TCM by SMA, during the course of this investigation. As such, they represent definitive "counsel" as to the topic(s) of concern. Essentially an abbreviated "Short Course" of sorts, on the subject: !f not in fact a cogent "Mini-treatise". A fine .overview, synopsis, in any case. Offered from -- by any reasonable. measure -- the "premier consultant" in this particular field. "Gratisn.......... ;scientist to scientist. Cooperating. Collaborating. Sharing. Learning. !n our particular case, as has been ongoing since 1973. Exemplifying -- epitomizing -- "scientific/ cultural exchange": Though "supplemental" reading(s) -- especially Aleksandrov, 1998; etc. -- is/are. certainly recommended. to those interested in delving into this aspect of geological science further. GENERAL OBSERVATIONS, C®MMENI-S, ETC. f36' S. M. ALEKSANDR®V. Selected purtior~s of a letter from SMA to TC~i, Sept. 14, 2004: "What t say about san>ptes? Of co~crse this is magnesian skarn. t read. article [sent by TCfti with an earlier letter] by L. Meinert about Whitehorse copper belt deposits (1986), that contain its characteristic analytical data fcr rock- forming and ore-minerals and composition of intrusive rock (see all tables ire his article). [Bold emphasis by TCM] 21 GMC DATA R SPORT ~ ~:$ Page. 23/127. As first result I think that temperature of skarn formation after .dolomites. in contact with: intruded granodiorite melts (content 58.3% SiO2) was- near 1000C (after F. G. Smith).. The granodiorite is product of assimilation of .country rocks by over-heating granitic _ melts (see my articles :.from 90's years). The absence in skarns. of monticellite zone are given possibility to suppose .its belonging to hypabyssal periclase facies of dolomite progressive metasomatism in magmatic stage (see fig. 16, 17, and 18, 24 in my book,1990}. its zortality is: granodiorite contact//pyroxene skarn :with spinel --- (+/- forsterite skarn). --- forsterite calciphyre --- periclase {brucitized) marble. --- host dolomites. All early pyroxenes are diopsides (Di > 90 mo!%}, but all safites are secondary {postmagmatic new formed} and. content Fe-component more as 10 up to 14-20 mol % hedenbergite. Forsterites are high Mg. May be are black magnetite? Diopside +spinel paragenesis on postmagmatic stage transformed in (into] a little Fe-content phlogopite as also forsterite +spinel rocks too. In the same time formed clinohumiteafter .forsterite in calciphyres. (Note: valleriite in this time of process is absent, it is low temperature mineral. Only at bast stages clinohurnite is .altered into brucite and magnetite, fullylosing F, and .appearance of sulphides may be doing its reaction withformation of hydroxosulphides.) Near intrusive rocks .took place development postmagmatie secondary calcskarns after part pyroxene zone of Mg-skarn rocks with appearance salites, vesuvian?. Mg-amphiboles (actinolites .after salite}, garnet andradite-orossuiare composition .and woilastonite near granodiorite (fig. 63 in book). Mg-spinel is transformed .into gahnite. After granodiorite.. appear garnets of grossulare composition :and Fe-bearing. epidote as endoskarn minerals m postmagmatical associations. Sulphide mineralisation is next at the. fast ore step after secondary calc skarn (ar7d greisen): At low temperature, minerals you can.- see are brucite (after periclase), serpentine (after forsterite) and Mg-chlorites (after phlogopite). The presence of valleriite (in ores at Arctic Chief up to 30% !?, and North Star, see Meinert's article. Also see data of K. Harada, 1973, about Little Chief; Yukon and W. Petruk et ai, 1971} .........:.... The name valieriite is going for honor Swedish mineralogist. Prof. G. Wailerius (1683-1743, see Dana, et ai, Sulphides}. About genesis and role tochitinite-valleriite. Are common. low temperature .minerals in all pyrrhotite or mackinawite basic rocks (Mg-skarns,. kimberlite, gabbro, dunites, etc.). and in its are tochiiinite-or haapalite (as Ni-analog in pentiandite ores). The presence: in these rocks of Cu-sulphides is given start for formation vatleriites (for example, Chamberlain, J. A., De(abio, R. N., Mackinawite and valleriite in the Muskox intrusion. Amer.. Mineral., 1:955, v. 50, #5-6, 682-695). Its. formation .after Au, Ag, Pt, and. Pd-bearing sulphides assume appearance free micron [size/scale) particles of noble metals in mass of hydroxosulphides. The presence this shirt [coating] are giving big difficulty far sulphides flotation in extraction process and evoke loss of Au and Pt: r 22 GMC DATA REPORT' 3 4: 8 Page 24J127 Probable these particles in hydrothermal and supergene conditions are easily soluble and redeposited an larger metal grains as first steps for growth of nuggets. For Yukon climate is actual the presence of permafrost effect. This is promoted to {facilitates] increasing in many times concentration Au in rest solutions in ice freezing up to oversaturation and pass electrolytical reaction with redeposition as "new gold" of intermetat compound -(see valleriite article). .New data.. about sulphides: (with Au and Pt) from Mg-skarns of world. and vaNeriite-tochllinite will be published in Geochemical International in 2004. (#5, see Lebedinoe. Yakutia and others and #9) and 2005 (#3 and oth.) and I will. be send its for ybu.n "A few questions from me to you, Tom, if You ps:rmit: 1. What are spatial (geographic) correlation lode and placer Au deposits in 1rVhitehorse belt? 2 Are or not any boron minerals in deposits in the copper. belt? 3. In copies of article that you sent me, are very often data about presence in skarn hematite or specularite, that are: very seldom for- Mg-skarns. Probable this is Mg-Fe-borates: fudwigite or hulsite and its magnetite pseudomorphases? 4. From publications I know about presence Mg-Fe-borates (fudwigite? or hulsite?) on Swift River near Seagull batholith (southern Yukon). In contact zone Tho-npsan, R. M. from Univ. ( of B. C. (see introduction in Petruk .article) and Gower, L A. have described Mg-Fe-borates in sphalerite ores {American Mineral., 1954, v. 39, #5-!z.° .Selected portions of a letter from SMA to TCM, November 15, 2004: "All enclosed. materials by p. Tenney and others are- fully interesting to me. I am sure, that ore-bearing magnesian skarn may be mare widely distributed in western Canada .(see article about borates in North America). ®f course, it is necessary to remember, that near - contact with granitoids talc-skarns mini=_rals .can .have altered/replaced Mg- skarns and mask its presence, but magnesian minerals (forsterite, clinohumite, phlog©pite and pericfase} are c®nstantly present in marbles. {Emphasis by TCM.] Thank you for description to 'deposits near Arctic Chief in Whitehorse ore bait. About molybdenite: it is one last sulphide on gold skarn localities. I encountered it in phlogopite rocks in Eastern Chukotka, in altered ranodiorites in Yakutia,' and in rox ne- rn - 9 et ~y a ga skarns vdith Bi-sulphides and Au in Hoi-Kai North Korea. Greene mica-like minerals in skarns may be lip onite or phlogopite." 23 GMC D _ Pa 5 AT e 2 12~' AR EP 3 0 RT 4 8 9 "About temperatures of initial granitic. melts: It in normal dry granitic melt with 72% SiQ2 ~ (T melt is near 820C -after F. G. Smith:~Physical Geochemistry", who is giving data about T melted dry magmatic rocks from gabbro - 1250G up to pegmatite). is a little more. for melting exocontact pyroxene skarn.- For it T.must be near 1200C (See articles #28, 31, 32, 33 ). [[ln SMA °BIBLIOGRAPHY"/publecations list,. sent in a recent letter to TCM, See "REFERENCES section of present report.]j. For assimilation .basic host rocks is necessary ...presence high-heated granitic melt. What are any data? e in rnlted h f F 1 se rn Russ a t a s a t o book He mut G .Winkler wh' ive T 0 9 crystallised gabbro magma as 12000, syenitic = 9000 and. 800-700C for granitic, that: are similar with. c€ata F. G. Smith. From Winkler's data T host rocks is 1500 (?' only. The metasomatic process of alteration ®f dolomite started in halo intrusion under .action magmatic Si and 0~1-bearing solution and give primitive skarn tonality as first stage process (300-4000), but not 1500). The reaction CaMg[CO3}2 ---> Mg® + CaC03 + C®2 is 6t)0-7--Cf11Cm depths 4se~ fig. 1, 14, 19 and 32 in my book}. [Emphasis by TCM]. it is before the complication of tonality skarn column on stage' of melting near-contact rocks, that dem n m re hi h T and be com ni d wi h a earn w z n in lumn: a d o g ac pa e t pp ace ne o es co monforsteritic and enstatitic as plus Mg from melted part of exoskarn. The thickness of high magnesian zones = 1/2 the same [thickness]. melted skarns. This process impossible on contact with SOOC granitic melt. As you think about this? From my practical work f see, that near contact with skarn .after. dolomite, granites may {. transformed irz granodiorite.:....... up to .gabbro under assimiiiation of skarn material! Or .may. be leucocratic granites, too. Ali progressive Mg-skarn processes have place on contact with magmatic rnel s. After consolidation intrusion, took place regressive transformation the ..mineralogy of early formed skarns.H - "The presence Mg-Fe boraces on Whitehorse and other- area is .possible. t send you copy of Thompson. & Gower article." "! send you my bank in English (15th Nov mb r ,bibliography (articles published. ~ in English), and a .copy of my former .essay abo~~t ludwigites in first edition of " >, o h i r Ge c em stry , that eceived good compliment from W. T. Schaller many years ago.. Selected portions of a letter from SMA to TCM, nRarch 15, 2005: "'you are doin h I r t o a 2 investi a ion ar g g t d su orted ma nesian skarn natdr g p e of p q Arctic .Chief!!! Bt is good ;start for future regional observations, in Canadian 1 deposits!" .......... [Emphasis by TCMj 24 AMC DATA REPORT 3 4 -S Page` 26/1P7 "~irs# c®mmentaries for your samples: Common look - as also in Sro®ks Mountain and Tin Creek [Seward Peninsula, Alaskan in Arctic Chief r®cks. ( [Emphasis by TCM] You can see rhythmically-banded. textures, that inherit,. and in magnetite ores. (The .best you can see in TM-04-10-12-22-b-104 -_- [the sequence] around diorites' injection in marbles: exchanged ["altered"] diorite--clinozoisite rim--pyroxene skarn--banded ludwigite-bearing forsteritic calciphyre--banded. periclase (brucite) marble; in TM-04- 10-12-22-a-134 and -131 and -102. --- banded phlogopite--magnetite ores,' in -126 -- - serpentine/forsterite.. rhythm in magnetite;. in TM-04-6-9-4-2 --- is forsterite-- calcite rhythm, etc....). [Underlining emphasis by TCM] These textures have origin on progressive stage of metasomatic exchange of dolomites and reflected in ores-- see. book [SMA, 1998], .pages. 77-87. It is non-equilibrium process. My .first question: what is .position these little finger-like. projections of diorites in marbles .find. on contact with big {main) intrusive massif? It [`projection/s'J is shown in a few of your samples! You can see similar [features] in a few figures in book [SMA,1998J from skarn areas. Next my second question: Magnetite is absent near -those injections in marbles. What is position. magnetite ores in .metasomatic contact? .They are oNy in immediate contact zone of big intrusion? to your collection is splendid periclase marbles, but in literature are not this information, !n maw samples in marbles and forsterite-calcite environment are a bit to big -.black crvstais of LUDWiiGITE {see TM-04-10-12-22-b-115; -23 110 -23-108, etc. See Brooks Mountainf This fully are not in literature about Whitehorse copper belt+. [Underlining in above is .original in letter from SMA; bold emphasis added by TGM.J Third:- In .your collection I can not see monomineralic forsterite skarn, only calciphyresl You check up this. fact? The presence the last [monomineralic forsterite skarn] is possible after magmatic melting of the pyroxene skarns (see exchange. types of zonality --- see it in book [SMA,1998J). About. typical. lime skarn (TM-04-08-09-2) [ofJ pyroxene-garnet. composition:.. What is its position. with magnesian skarns?)believe that it has postmagmatic origin from Si-bearing marbles. What, haw much, are .sulfides in this type skarns?? Or absent? In forsterite marble (TM-04-6-9=5-1) is spinet .The part of pyroxenes is-Al-bearing. In this situation is formed late phlogopites in rocks and ores ............. 25 6MC DATA REPORT 3 4 ~ Page .27/127 Conclusion: Contact aureole at Arctic Chief was formed in normal dolomites. Its tonality is near the primitive type, but it is [in/of] the hypabyssal periclase facies (see..pages:.3t-37, and fig. 24, in book [SMA,1998]) in the..time of progressive metasomatism of these rocks. Thee first postmagmatic ore miners! in marbles is iudwigite; after forsterite formed clinohumite (TM-04-6-9-4- 2) and phlogopite -after spinet. The part magnetite is inherit textyre of calciphyres, other - the -same with phlogopite - fr®m pyr®xenic skarns. All sulfides are late. (Emphasis by TCM.] in Whitehorse copper belt are (many] deposits and prospects.- .........: [How many/what proportion] a# [these] are seated in dolomitic rocks? If only part of [this total], what are the differences in the composition of skarns and ores composition in not-dolomitic environment?" [Which of course is another matter/study yet to be deaK with. {TCM}] Selected portions of a letter from SMA to TCM, June 16, 2005: "Answers. to your questions: 1. For study (investigation) ail .pure da~lornites, periclase marbles and forsterite ~- spines calciphyres [it is] very useful to see its weathering starface. You can see ail silicates as praminences, but in place of brucite wii6 be caverns! it is important to watch!!! jEmphasis by TCM. Remindful once more of the personal/learning experience on Brooks Mountain in1.973, recounted previously, above.] 2. About magnetite ores in skarns. Yes, it is common in direct contacts with main intrusive f bodies, but near. magmatic injections in marbles are rare. Presence iron you can see as iudwigite or late sulphides (pyrite and pyrrhotite). Magnetite is often replaced of silicates in skarns: Alt iron is coming from .solutions in time of postmagmaticatly exchanged iron-rich minerals in basic intrusive rocks.. Only from leucocratic granitic magmas Fe is going on magmatic stage and. giving magnetites of syngenetic with the formation of magnesian skarn tonality {see book [SMA,1998]). 3. Monominerafic forsterite skarn zone [indicates] magmatic :stage replacement of magnesian skarns near intrusive rocks by melt. Half thickness. of monoforsterite 'zone =thickness melted skarns. 4. 'typical skarns are formed after postmagmatically .changed silicate- bearing carbonate rocks. After pyro~enes is formed zoning garnet. `Arsenopyrite'? in sulphide ore can be loetlingite -FeAs2!!! Check it!!' [Emphasis by TCM] 5_ The CaC03 marbles in contacts with granodiorite melts are n®t transformed -into skarns Ca is assimilated by melts and involved in Ca- beating minerals - plagioclase, hornblende and etc. C®2 increases." .[Emphasis by TCM] Selected portions of a letter .from SMA to TCI~, June 25, 2005: ~ 26 GMC DATA REPORT _3 4 8; Page z8/iz~ "About dykes and its composition. In last letter I note about leucocratic hornblende quartz monzonite dyke.. It is possible that monzonite from massif will be more basic! If this so /well them you -can think that monzonite magma of massif is result of assimilation of host rocks and' f 1 rimer melt was mor cl e e os to rani i c m i ~' p Y g t c o os Lion and .was su erheated. Last d kes fro p m p Y deepest magmatic camera must be leucocratic. In book [SMA, .1998} {Fig. 13) is silustrated this, and similar ..with Arctic Chief. Locality. [Emphasis by TCMj. (fn text, epidote = clinozoisite). Plus, see green amphibole with plagioclase in ..quartz-monzonite dyke- TM•04-10-12-23-108; 1`10•with pyroxenes and quartz." Selected portions of a letter from SMA to TCM; ,lanuary 11, 2006: "I am believed that .Arctic .Chief and othi~r deposits in 'Whitehorse ore. belt are best objects for investigation position and zoning Mg-skarns and ores in its. The- understanding. of genesis and mineralogy must be given the key ia~ exploration {discovering} new ore bodies in skarns and marbles .and its.. relation with placer accumulation of gold in Yukon region ire alL [Bold emphasis is by 7CM; underlining is by SMAj In my works i only want to demonstrate (show) that. skarns after dolomites are sources many metals and raves [materials} in any parts of al( world. Of course in past and to-day its was mining and without this understanding, but aplay [applied} geochemistry may be given: goc>d results for its prognose." [Emphasis by TCMj Selected portions of a letter from SMA to TCM, May 11, 2006: "Your commentary in {attars, best. slidea [photographic} from quarry, and, 'of course, the good-.samples itias given me the possibility to support the magnesan skarn nature of (this) Canadian Fe-Cu-deposits ' in Whitehorse ore belt." "Your last samples is very best: its illustrated ®f rhythmically-banded structure. of rnetasomatites !!!" [Emphasis by TCM] ®ther selected comments (SMA}: `Periciase marble' [ie. marble featuring brucite after periciase, and calcite, +/-} is the predominant `host rock' representec4 in the [rnac~yj specimens studied. [Emphasis by TCMj Forsterite and low-F ctinohumite occurs. in calciphyres. Rhlogopite-magnetite ores. 27 GMC DA3'A REPORT 3 ~ S~ Page. 2..9/127. Zoisite occurs after plagioclase-pyroxene zone (or diorite in rocks studied.. In comparison with. the areas such as lost River,: Brooks Mountain, Tin ( Creek, etc. on the western Seward Peninsula, Alaska, [where `SMA.- and TCM worked :together in 1973 and 1979] at i;he Arctic :Chief locality -the situation appears to be not as complex. [Emphasis by TCMj OBSERVATIONS ON SPECIFIC. SPECIMENS (S. M. ALEKSAN®ROVj: TM-fly-5-25-1-Q: "Probably in this specimen is ludwigtte in the marble part near contact with forsterite- magnetite ore. .........." "Marble with ludwigite (??????) as black needles . ...........:" "I will be send you new [[rnicroprobe]j analytical data for sample #TM-05-5-25-1-Q {marble with Ldw?????? and + magnetite ore......._.... )„ [An excerpt from aletter-from SMA to TCM, May 11, 2006 states: "All black needles are pseudomorphoses magnetite after boraces .......:...:."j "Other minerals in this specimen: Mg-bearing magnetite- {>90°/a FeO, and 1.5% MgO) Dolomite- (22% MgO, 30% CaO) Serpentine- (36% MgO, 3% Fed, 45% SiO2} Phlogopite, altered to clinochlore- (with MgO, SiO2, and AI2O3) Talc- (MgO, SiO2) .Are [also] Fe-Mn species dolomite/ankerite." Selected portions of a letter from SMA to TCM, June 16, 2005: "Ludwigite is in serpentine-bearing marble TM-[flaj-10=1'2-22-8-104, very tittle. May be in contact with marbles you- can see k®toile Mg3(B®3}2??? [Emphasis by TCMj Near monzonite plag and prx -- transformed into zoisite and calcite; and prx -- into Mg phtogopite: All periclase in marbles fully. transformed to brueite, .with calcite; its form is pseudomorphic after periclase. In these. rocks are a few grains of .forsterite and ctinohumite: In magnetite ores forsterite is transformed into serpentine near catciphyres, or into. other silicates --- into Mg-phlogopites (after dtopside). Mg-pyroxene is in TM-04-10-12- 22-A-137 and actinolite....:... 22-B-.117, amphibotes....:... 22=A-101.. Green amphibole with plagioclase in quartz-monzonite.- dyke- TM-----23-1.08, 110 with pyroxenes." ®ther comments on selected specimens (SMA): 2 t3 GMC DATA REPORT 3 4 8 Page 30/127 I'I TM-D4-TO-1 2-23-1 1 1 Skarned zone on contact .with dike. Content anorthite, `pyroxenes (fassaites} and garnet. The t icat in contac m n - t a esian karn la ioclas~e oxene com ositi n and YP 9 p 9 Yr o secondar -il p p Y I Yl ! transformed in into salite- arnet bearin associations. [ 1 g 9 Microprobe analysis: P-67-1. Salite, plagioclase (anorthite), garnet (grossularite 70%, andradite 30%), pyroxene. TM-04-10-12-22-B• 104: Forsterite-bearing Brucite (after. periclase) marble, with calcite, serpentine and: phlogopite. .Microprobe analysis: P-67-2. Forsterite, serpentine, Brucite, phlogopite. TM -04-10-12-22- B-1 19: Brucite-periclase marble. - Microprobe analysis: P-68-1. ,Brucite with relicts of periclase, .and dolomite + spinet hydrotalcite (after. spine!) and magnesite. TM-04-1 D-1 2-22-A-1 1 3: Brucite-periclase marble, with Forsterite and clinohumite. Microprobe analysis: P-68-2. Brucite and periclase, some dolomite. TM -04-1 0-1 2-23-B-1 1 5: Brucite (after periclase) marble with forsterite. TM-04-1 0-1 2-23-1 1 0: Plagioclase rock with hornblende and pyroxene (dike?). ( TM-04-1 D-1 2-23-109: clinohumite calciphyre wittl magnetite. TM-04-8-9-2-Z: Vesuvianite (idocrase)-pyroxenic typica8 barren skarn. TM-04-1 0-1 2-22-A-1 30: Magnetite ore with phlogopite. TM-04-10-12-23-108: Plagioclase rock with amphibole (dike???). TM-04-1 0=1 2-22-B-1 41 Magnetite ore with serpentine. T M -04-1 0-1 2-22-A-1 31 Magnetite ore with phlogopite; magnetite is prismatic. TM-04-1 0-1 2-22-A-1 34: Magnetite ore with phlogopite; magnetite is prismatic. TM-04-1 0-1 2-22-A-1 32: Magnetite ore with phlogopite; magnetite is prismatic. 29 6MC DATA REPORT 3 ~ 8' Page .31/127 TM-04-1 0-t2-22-A-1 35: Magnetite ore with. phlogopite; magnetite is prismatic. TM-04-10-12-22-A-137:. Diopsidic skarn :with prismatic magnetite. TM-04-1 0-1 2-22-A-1 33: Phlogopite-magnetite ore. TM-04-10-12-A-126: Rhythmically-banded serpentine-magnetite ore. TM-04-1 0-1 2-23-106: Rhythmically-banded serpentine-magnetite ore. Serpentine after forsterite. TM-04-1 0-1 2-22-B-1 1 4: Rhythmically-banded serpentine-magnetite ore. Serpentine .after. forsterite. TM-04-1 0-1 2-22-A-1 01 Actinolite in magnetite ore. TM-04-1 0-12-22-B-1 1 7: Actinolite after diopside, in magnetite ore. TM-04-1 0-1 2-22-A-1 21 Phlogopite in magnetite ore. ( - TM-05-10-T3: Rhythmic-banded marble with sulphides. SOB>!iE ®l3SERVATI®fVS (TCIVi); The .foregoing (2004-2007) work of S. M. Alek~androv` -- analyses, results, observations, interpretations, comments, etc. -- provides definitive characterization, and .elucidation,. of a number of key aspects. of petrogenesis and associatedlrelated mineralization at the .Arctic Chief ore deposit .Affording insights previously not perceived-- or if perceived, apparently not fully appreciated -- at this, or other/similar localities within the Whitehorse Copper Belt, or elsewhere in this region. While, additionally, offering definitive confirmation of the comparable interpretations developed, :and conclusions put forward -- though somewhat more tentatively, by two of his "apprenticeslproteges." -- during the course of our earlier (1980-1982) study. The results of which, regrettably, remained ,unpublished, unremarked upon, since. that lime. This research,- collectively, c~nvincingiy revealing a number of .features of ;appreciable ..geological significance. These having been apparently unrecognized prior to our studies. In particular,shedding some new light", as it were, on the Arctic Chief locality. With atfendant implications .elsewhere in the Copper Belt; perhaps regionally, and elsewhere. t - 30 i ~~fG DATA REPORT 3 4 8 Page 32/127 ' ~II _- As well, our collective studies of the Arctic Chief have provided additional evidence -- yet one more example ;--supportive of the approach to magnesian skarns, and associated mineralization, developed by Aleksandrov and his associates, over the course of many years of extensive, as well as intensive, investigations. Affording an important perspective for further consideration. Our initial (1980-1982) studies at the Arctic Chief entailed fieldwork and sampling. of the -gamut of .materials, and field- relationships; available for studyfexposed at that time. This .included .the "calc-skarn" materials, .and the "late dykes", as well as the (variously) "carbonate" rocks and the "ore" materials. Selected representatives (a substantial number) of the spectrum collected were analyzed in the laboratory (utilizing optical microscopy, in transmitted as weir as reflected light; x-ray diffraction; x-ray emission .spectrometry), as appropriate. Results of this are presented, discussed, variously; in the present report, above. Due. #o .constraints of time, distances, budget, our subsequent (2004-200 .work was focussed 'principally on the "carbonate" rocks 'and the "ore" materials. These considered to represent/fieature the major portion of the' significant "keys" to the aspects of petrogenesis and mineralization fundamental to. this locality, and other similar occurrences.. Though some attention was. again devoted to investigating the "calc-skarn" materials, as well as the "late dykesn, as convenient, andfor deemed appropriate. This included "fieldwork and related sampling. Subsequently, a number of "selected/triagedn representatives being .mailed to Alseksandrov for his information, and use as he deemed appropriate. ( Results of these later, somewhat "more limited" efforts, regarding calc-skarn and dykes are presented, variously; in the present report. Essentially "supplementaln, as it were,. to our principal concerns at this stage of our rather lengthy -- though interrupted/perturbed. -- "over the course of the years studies here. ` Featuring a number of comments, etc. by SMA, interspersed among the others in the selections from the "SMA to TCM" correspondence (the "Aleksandrov -short course/ treatise"}, presented. above in this report. .While most of the first author's observations on these -- and the other -- collected materials: are to be found in Part 2 of this repo~~t, the separate "Data Supplement" addendum. Somewhat scattered about, among results of .fieldwork, photography, sample collecting; preliminary examination, subsequent 30x/60x atereo-microscope examination, petrographic microscope examination of selected materials as grains-in-oil, and other comments. With regard. to another issue {just one of many) of "reality-related", "less-clearcut", geological character. Namely, those not at all uncommon situations (eg. the V~/hitehorse Copper Belt, as summarized in lNatson, 1984) in the realm of sedimentary petrology/stratigraphy, featuring "interbeddingn; and/or variously "impure" lithologies vvithin beds. Vrlith 'a range of possibilities thus afforded as to the "nature of precursorial host rocks", vis-a-vis skarn formation. and. associated mineralization. "Geological trash cans", sedimentary rocks; to varying extents of course. "pure" being a relative .term in the lexicon .for these materials: Variously' °muddy/argillaceous/dirty" carbonate rocks as a retevant example. featuring various proportions of fine/very fine/"clay-size°(<2microns e.s.d. constitu n { )_ a ts. Generally consisting principally of silicate minerals, such as one or more. varieties of "clay minerals»; 31 GNIC DATA REPORT 3 4 $ Page 33/127 variously weathered micas, feldspars; quartz, +/- etc.. While: other complications are. not unlikely, in .terms of chemical/mineralogic composition, dtae to diagenetic,` alteration, effects. Combined with "interbedding" of sedimentary deposits, somewhat complicating matters of interpretation, °prediction", of skarn-type/details thereof. from a given host rock... assemblage. Certainly "variations", "ranges", are not unlikely... Though remaining, principally, a .function `of "the nature. of the host rock(s)". This of course relevant to the comments in the present report as to the importance of the nature of the precursorial host rocks with regard to skarn formation, etc. Implications including characteristics, and genetic aspects, of calciphyres, and talc-skarns, in particular. It should be pointed. out that the characteristics of "calciphyres", as put. forward. in the foregoing discussion of these rocks in an earlier portion of the present report (COMMENTS. ON RESUbTS FROM THE 1980-1982. STUDIO have. been subject to alternative interpretations, past and present. Such principally having to do with presumed inhomogeneities (viz.. sedimentary layering, and/or interbedding; and/or "impure/dirty" lithologies) within the precursorial host rocks. Though in the case of "calciphyres" as treated by the present authors, the extensive, as well as intensive, detailed ..work of Aleksandrov arnd his associates (cf. the REFERENCES section of this report; especially Aleksandrov, 1998) seems to relegate proposed alternatives of this sort to a "less-likely" status, if not in fact refute them. Appreciable evidence. having been developed indicating metasomatic processes, at the elevated temperatures /"PTC" conditions attendant to the associated igneous/metamorphic environments clearly present, as responsible for the formation ofthe features observed in thESe rocks. While the similarities of spatial "position, "zonality",.which are common to magnesian skarns also suggest origin(s). other than due to the more inherent vagaries of sedimentology/ stratigraphy. ..The matter seems somewhat more complex, as to the "calc-skarnsn. Though not dissimilar. As mentioned in various comments by Aleksandrov elsewhere in the present paper; dealt with in more detail in a number of his other publications. The "nature of the host rocks" remaining a/the key factor. In one guise or another. Some "asidesp, from a "friend of skarns, etc.°: .The Arctic Chief locality represents a fine example of contact-metasomatic magnesian skarn, and associated mineralization. Manifesting rather well various key. characteristics of its petrogenetic, and related ore deposit; aspects. As such,. it has afforded we three investigators much in the way: of opportunities in terms of geological research. Appreciably furthering .our individual, and collective, levels of knowledge. Enabling us to develop the interpretations presented in this report, While it is fully appreciated that, in all likelihood, there .remains much more to be learned here, at this fine locality, Thus, while carrying .out fieldwork, sampling, etc. chores, over the years, the first author also found himself becoming increasingly. "fond" of the Arctic Chief and environs. From the admittedly perhaps somewhat bias8cf point of .view of this former (among other things) Professor, .this locality .seems well-deserving of further studies.. Preferably of "thesis-type". Bringing to bear youthful vigor, <~gility; "new ideas/methods"; etc. With the view to extracting as much information as feasible from this wondertul site. As well as exposing. another generation of geologists to this locality, its features. As a -fine example of its kind. to hopes of continuing the always-tenuous thread of knowledge, as focussed in this case on the principal theme addressed in the. present report. 32 GMC DATA REPORT 3 4 8, Page 34/127 With the-view to further advancing the state of knowedge as to this particular realm of geological science. i3uilding upon the previous efforts. here, and elsewhere. Adding to the Burn total of human .knowledge regarding the. subject matter of concern. Before the inexorabilities ofi t time and exposure to the elements --..natural, as well as "cultural/anthropogenic" -- take their inevitable toll here. .Which unfortunately .has occurred recognizably betvreen earlier and morerecent experiences at this excellent example ofi the type. These fine rocks, etc., are too good to merely go to waste. Without at least studying them -- the rocks .and. ore- materials, the relationships at thin locality. -- further. As thoroughly as at a!I feasible. Extensively, intensively. All sorts of possibilities came to mind as to "opportunities/ avenues of research investigations".which .might be pursued. here... The list expands each time one gives the matter any. thought at all. A "Geology Museum", the."AC"; as is the. Whitehorse Copper Belt, for that matter. The mere notion of "exploiting" these `"splendid" periclase marbles, or .other "eloquent" ..rocks hereabouts,. for. cement material, rip-rap, decorative stone, fireplace rock, road. metal, landfill, etc.; or of using the site as a "dump"; or whatever, is disquieting.. To say the least. Such possibilities probably ought not to .even be mentioned . While of course, to this writer, "selective exploitation", such- as re/ geological specimens in particular, on the other hand, :seems to' represent a legitimate, somewhat "higher", ,use. Pursuing this thread in another .direction. Surely numerous individuals in the Whitehorse area, as ..well. as elsewhere, who have had considerably .more .experience working on -- and "in° -- the. Copper Belt than the present writer, potentially have a great deal to offer as to_ various aspects of the work presented in this, or other such, reports.. Likely much of such ...valuable "info" not "published"; nor even "diss€;minated". Experiences, perceptions, notions, ideas, whatever. Perhaps even data, etc. !n the context of this "new. millenium",in which we now find ourselves, in particular.. as ( regards mineral resources, economies, "world affairs", etc., it would seem to behoove us to not overlook potential further contributions. of "skarn-related" mineral deposits. The accrued .experience, .knowledge, examples, of such, as epitomized by the .Whitehorse Copper: Belt,' and elsewhere in the region, ought to merit some serious efforts at "solicitation; unearthing; collection;. compilation". With the view to assembling as all-encompassing a "corpus" of . information, knowledge regarding. the subject, .the region,. as is reasonably readily attainable. Perhaps facilitated, initially/early on, by some. sort a# "geo-forum" affair/seminar/etc. Whitehorse representing an obvious choice of venue.: Featuring, .insofar as feasible, utilization of `the. available "geo-materials" themselves. The localities; such as remain reasonably .accessible, with the geology, the rocks, similarly accessible. Providing opportunity for the sites, their constituent materials, to "speak for themselves". To geo-types, young and otherwise. Hopefully. catalyzed by those other "geo-materials". Those knowledgeable individuals alluded to above. The ones with the extensive, and intensive,. fiat-hand experiences on the Copper .Belt. Featuring those erstwhile New Imperia6 fViines/Whitehorse Copper Mines types - - now "alumni" -- in particular. Among others, certainly. Just some ideas. "Geo-phantasy", .perhaps. From yet another of those "Variags". The "Vikings"; "the ones from out-of-town with all the, ar3swers" (S. M. Aleksandrov, personal communication,1973). Which the Whitehorse Copper .Belt has seen so many of, suffered so .much from. Yet -- generally -- graciously accomodatec, humored, over the years. For which this particular example of the ilk- o°ffers grateful, acknowledgement, sincere appreciation. t -------------- -------- ------33--------- -- ------ - ---------:. GMCDATA REPORT 3 4 $ ' Page 35/i2i .SUMMARY AND CONCLUSIONS: The. present report is` intended to convey the. following points: These investigations were pursued in the context. of concepts regarding skarns .which have been developed and elucidated overmany years. As summarized and presented by S, M. Aleksandrov in his definitive monograph "Geochemistry of Skarn .and Ore Formation in Dolomites" (1998), and also .dealt with in .his numerous other contributions. to the technical .literature.: Including his. recent :(Geochemistry International, 2007, v. 45, No. 2) paper, entitled "Gold Behavior during Endogenic and Supergene Alterations of Sulfides in Magnesian Skarns". A portion of this paper features the- initial publication of our cooperative work on the Arctic Chief, and. results, interpretations. This locality serving as one of several deposits exemplifying key features relevant to his topic. Provide a statement of the recognition and. confirmed occurrence of periclase (brucite). marbles at the Arctic Chief (west) locality. As .well as recognition and confirmation of" similar occurrences at the Little Chief and Black Cub South localities in the Whitehorse Copper Bett. Comment on the significance of the formation of periclase (brucite} marble, in terms of the results of .experimental petrology,. known phase .relationships, mineralogy, geochemistry,. etc. Note the importance of this, in the context of these localities, and elsewhere. Emphasize. that the formation of periclase, as well as its (partial to apparently complete) replacement by brucite,. both provide substantive insights as to petrogenesis, geochemistry, geological relationships, and mineralization, of potential value in a number of ways. Observe that this apparently "initial recognition" of periclase (brucite) marble at the Arctie Chief (west), as well as at the Little Chief and the Black Cub South,. suggests that perhaps further reinvestigaiionlreconsideration is merited of these, as well- as. associated rocks, "skarns ; and mineralization in the area, the region, and elsewhere.. Such periclase (+/- brucite) marbles -- and associated/related materials , -- perhaps (likely), lurking, as-yet-unrecognized/undetected/(unsought), elsewhere,: in this, and other, regions. With attendant implications, scientific and "otherwise", regarding any such .yet-to- be-recognized occurrences. Among which implications,"practically speaking", recognition -- distinction as such. -- of periclase (+/- brucite) marbles (and/or dolomite/"dolomitic" carbonate rocks as well) perhaps .representing a potentially useful "exploration guideu. .Provide as well the initial ,reported recognition of the presence of "calciphyres" at the Arctic Chief (west) locality. "Marble-like" rocks. of predominantly carbonate composition, featuring a number of key mineralogical, geochemical, and textural characteristics, as well as _ spatial relationships, indicative of a magnesian skarn situation. Displaying typical banding of (variously) "rhythmic"..character, attesting to metasomatic activity. Note also the initial reported recognition of similar ("rhythmic°) banding (°inherited") in °ore" specimens; featuring .magnetite, +/- sulfides, (+!-), and associated ~'~ "bands"/"layers" of forsterite/serpentine/phlogopite, +/-. Further indicative of .the "magnesian skarn" character of this mineral deposit. While also affording significant evidence as to the .nature of the deposition. of the ore material(s). 34 GMC DATA REPORT 3 4 $ Page 36/127 Provide the initial reported recognition, and confirmation by Aleksandrov; of the formation (with subsequent pseudomorphous replacement. by magnetite} of Mg-Fe borate mineral{s) -- "magnesian-ludwigite° -- in rocks at the Arctic Chief (west) locality. This is of relevance as additional evidence as to the "magnesian-skarn" character: of this locality,- and is also, of decided. interest in a number of other ways. Thus; to our knowledge, this-.work has resulted in the first recorded .elucidations, and confirmations, of the presence -- individually; and as a geological "spectrum" of significance as well -- of periclase (brucite) marbles, associated calciphyres, rhythmic banding in rocks, and in ores, as well. as -the occurrence of -Mg-Fe borate mineral(s) of the ludwigite-vonsenite series, at the Arctic Chief (west), or elsewhere in the Whitehorse Copper Sett and environs. Compositionally, texturally,. spatially manifesting the sequence of geochemical. and geological events, relationships, recognized and elucidated by Aleksandrov. and co-workers; the "position(s)°, and thee."processes" attendant thereto. As recorded in, evidenced by, the rocks and the ores. Featuring; as a matter of "position" (geologically, :spatially,. as observed in the field), the apparent relationships (displayed at various scales, up to deposit dimensions) of: igneous rocks of granodioritic--quartz-dioritic--dioritic character, "(calcic-)skarn" materials --- pyroxene, .garnet, +/- ; relative to the. principal ("ore") occurrences. of magnetite and -other ore-minerals;.. the. (generally) relatively more "distal" calciphyres; relative to the further-distally-positioned periclase (brucite} marbles, these' representing the "outer. zone of the contact. aureole". Individually, and collectively, these factors provide clear evidence of the magnesian skarn" nature of this locality. As .well as being consistent .with the concepts .developed by .Aleksandrov and colleagues. Supporting a suggestion, here, far consideration of the foregoing, in the overall context of "skarns", related .mineralization, etc. Advancing a recommendation for "reconsideration" of (at least some/certain aspects of) "skarn° -- and related ore -- .formation. As well as implications -- geologic, petrogenetic, geochemical; mineral resources: Per Aleksandrov (1998, 2007, and numerous other contributions to the technical literature).... The Arctic Chief (west) locality is demonstrably an example of a "magnesian-skarn". As our work. has .further shown, in particular. it features a version of "primitive-type zoning°, in this case developed/formed under the geological conditions of the "hypabyssal periclase facies", as considered in; the context: of the modE,l of skarn-formation. elucidated and refined by Aleksandrov. and co-workers over. a period of many years. This model merits attention regarding the nature and origin(s) of "skarnsn, particularly with regard to those.. associated with "host" rocks of "dolomite/dolomitic/magnesium-rich" character. The composition of the precursorial/host rocks being a principal geochemical factor. The model affords a valuable conceptual, as well as substantively based, .framework of theoretical background, fundamental knowledge, and relevant experimental .work. As well, it offers ample. evidence (the Arctic Chief, as just one more .example), from a :wealth of experience.. and analytical. work, supportive- of thF: validity of this. approach to the genesis of skarns. 35 GMC DATA REPORT 3 4 $ Page 37/127 Appreciation:, and utilization, of his approach ought to be an essential aspect of investigations d to further the understandin of such eol ical occurrences.. In turn, potentially intende 9 09 9 yielding insights of "more practical" value in the exploration for, evaluation of, and production of mineral resources from deposits relatedto magnesian skarns. Such as has been the case in many areas, worldwide; as attested to by the experiences of Aleksandrov and `associates. The presence -- or absence -- of magnesian skarn, or'subsequent modifications thereof, in a particular "contact metamorphic/metasomatic" geologic environment/occurrence of skarnlike character has decided relevance in terms of the likelihood,-and nature, of associated mineral deposits. Extensive ..experience elsewhere has indicated, essentially demonstrated, that magnesian skarns are particularly '`fertile ground" for the formation of related mineral deposits of several kinds. Including, possibly, precious metals} "nugget" formation. Further pursuing the theme, to our knowledge, this work, per Aleksandrov's discussion in his 2007 paper, represents the first such treatment {at least published in the open literature} of the Arctic Chief from. this. particular viewpoint. of the .genesis of skarns and related ore.. formation. As such; it offers a somewhat different perspective than apparently has heretofore been brought. to bear on this subject, at this particular locality/deposit,, or in .the Whitehorse Copper .Belt, or in the region. Or in many other: areas This would seem to be a perspective meriting more extensive appreciation, consideration, application than previously has been the case. Dr. Aleksandrov's comments regarding the Arctic Chief, based on information/data derived from -the other sources he cites, in addition to our own, demonstrate the apparent applicability, "utility", relevance of this "model" to .this particular Locality/deposit. As well, in the context of this model, and its demonstrated.' usefulness elsewhere, suggesting possible implications with regard to .skarn and ore formation elsewhere in this region too. Possible relevance to the formation of placer depositsbeing.. among these implications. Our 2004-2007 investigation also resulted. in the recognition of some interesting .occurrences of molybdenite, and other .associated sulphide mineralization, in the Arctic Chief area. Aspects of this are discussed in this report, Part 2, the "Data Supplement" addendum. .Implications of any/all of the above points, locally, elsewhere in the Whitehorse Copper Belt and environs, as welt as regionally, remain. to be evaluated. As may be appropriate, pursued further. (Per our late lamented colleague R. S. Dietz, who once told me that. he "always liked to try putting a ,little different spin on things".) Communication. regarding this work should be addressed to: Thomas C. Mowatt Post Office. Box 1438 Haines,. Alaska 99827, USA ~ (907) 766-3770 36 GMC DATA REPORT 3 A ~ Page 3_/127 ''~ ACKNOWLEDGEMENTS: Acknowledgement of the "scientific/cultural exchange programs".between the governments of the.(then) U.S.S.R. and the U.S.A. (n the case of the. authors of this report, a most successful. ` example of such efforts. In many ways. Would. there were more efforts of this'sort ;........ Stanislav M. Aleksandrov is gratefully. acknowledged for all he has done for the authors over the years. Personally as welt as professionally representing one of the more significant individuals in our lives. and careers. Sincerely appreciated, ail of it. Thanks, Stan...:........ 1980-1982 Study- June. C. Mowatt; Geologist, (deceased December, 1992), is remembered as wife, and. valued professionalcolleague, of TCM for some thirty-three years. An astute scientist,. demonstrating skill and dill ence in the .field and under round , laborator ,and office as ects of numerous Y 9 ( 9 ) p collaborative eolo ical endeavors includin this stud . 9 Y 9 9 .The cooperative members of the staff of New Imperial Mines responsible for "hosting" those informative "visitations/tours" during 1970 are acknowledged, with sincere appreciation. The generous cooperation and assistance furnished by staff of Whitehorse Copper Mines. Ltd. during subsequent 1973 "tour/visitation" occasions, as well as the. later 1980-1982 study,- .. is gratefully acknowledged. This featured .valuable office, field, and underground sessions with a number of individuals -- geologists, engineers, and others. Dirk Tempelman-Kluit, Geologist, Geological Survey of Canada, then on secondary assignment to Whitehorse, was most helpful. Sharing time and ideas,.. observations and insights; providing encouragement and assistance. All strong determining factors for us at the time.. Colleagues with the U. S. Bureau of Mines (1975-1982): John Mulligan, Mining. Engineer and Chief, Alaska Field Operations Center: appreciation -for support and collegiality over the years. Uldis Jansons, Geological Engineer: valued colleague since 1961. Among. other.. positions; formerly Chief Exploration Geologist with Cyprus Anvil Mining Co., .Faro, Yukon, for a number of years. Subsequently (1976 - cm) with the U. S. Bureau of Mines. Tom Pittman, Mining Engineer: valued colleague. Kevin Weir,. Laboratory Technician: appreciation for. excellent attitude, admirable aptitude. 2004-2007 Study- Sonya A. Mowatt provided invaluable, encouragerent .and support; as well as assistance in field- . work, sample=collection/hauling, "bear-watching" services, .literature searches, computer work, Russianlanguage knowledge, etc. Not to mention patience and understanding. "JED"....... 37 GMT DATA REPORT 3 4 8 Fage 39/127 Sharon Prien, of the ARLIS Library, Anchorage, Alaska, once again provided invaluable assistance and support. Efficiently providing reference materials, inter-library loans,. theses,:.. copying services, etc. in timely -and useable -fashion. All greatly appreciated. The welcome assistance of Mike Burke, Geologist, -Yukon Geological Survey, Whitehorse,. has ; been most helpful Our "inital contact" in 2004. Continued cooperation, sharing of knowledge, insights, and. personal accessibility are greatly appreciated. Mike was also responsible for providing the essential element of an introduction to Jim Coyne. The subsequent work during 2004-2007 would not have been. possible withou# the continued. interest, cooperation. and amiable hospitality received .from Jim Coyne, Kluane Drilling Ltd., Whitehorse, representing the. present owners of the Arctic Chief and some other localities. (Special thanks to Jim and Mike for their informative and valuable °tour-guiding" .services during initial .revisits to the Copper Belt in 2004.) Rick Zuran, Consulting Geologist, Whitehorse, generously provided time; .shared knowledge; offered perspective, helpful comments, and insights. I The knowledgeable staff. of the Yukon Energy, Mines. and Resources Library, Aimee Ellis, .Manager, provided assistance, .guidance, and a wealth of information, as well as a place of refuge in which to work.. The courtesies extended are greatly appreciated.. Ron Brockway, Geologist; colleague and friend. Acknowledged for, among other things, demonstrating by his fine example the level of information to be had "merely" by investigating rocks with the stereo microscope. Providing a .most valuable tool; as well as sharing techniques, perspectives, insights. Thanks, .for it all, Ron........:.. Special thanks to James E. Adler, Geologist. President,. On-Line Exploration Services, lnc., Anchorage, Alaska. Valued friend and colleague of many. years. With appreciable and varied experience in matters related to geology, mineral resources, and. mining. Combined with a special blend of astuteness, acumen, and attitude; as well as an impressive wealth of knowledge related. to things geologic -and otherwise. Making him a resource in himself. Association with Jim, professionally as weft as personally, remains stimulating, pleasurable, and rewarding. John W. Reeder, Geologist. Curator, Alaska Geologic Materials Center, Division of Geological and Geophysical Surveys, Department of Natural Resources, State of Alaska, Eag{e .River; Alaska. Valued colleague and friend for many years. As well a personal acquaintance of S. M. Aleksandrov, from °the Seward Peninsula jays". One of a kind. In keeping with-thee facility, and its contents,-entrusted to him. Like Dr. Reeder himself, the "GMCn :represents an extreme) valuable asset to the State of Alaska; and to all concerned with the geological Y sciences; energy, mineral and water resources; agricultural, engineering .and environmental concerns, Where else would one choose to deposit samples and data. for safe-keeping, as well as availability, and, hopefully, perhaps further use to others? While Alaska and the..Yukon Territory .are- of course "next-door-neighbors", geologically and otherwise. Thus, with. special acknowledgement and appreciation, for -many things.:.:: Thanks, John...... The continued. interest and support of the Berkeley Blue Group, is acknowledged with appreciation. Associates B. Barclay and B. I. G. have provided invaluable .assistance; commentary, perspective, etc. Your knowledge and abilities never cease. to .amaze.,........ - 38 6MC DATA REPORT 3 4 8 Page. 40/1,2 Special acknowledgement to P. M. P. d'le Phrogge, Geologist, retired. Friend and colleague of many years. Generously donating time and talents, as "a perpetual post-doc". A "man of few words", but a fine "sounding board°. Diligent, reflective. Keen of eye and mind. Doesn't miss much. A "good shipmate". Thanks, Max....,... Roman Rudnytsky, Pianist superb. For valuable musical "accompaniment" during the course of this project.. Recorded. As :well as, on two memorable. occasions, in concert. In Haines, Alaska, of a1lplaces.- Thanks especially for the "Colonial Song", Roman........ V. L Vysotsky, "Russian. Bard". Appreciation for providing a motto......:... REFERENCES: Aleksandrov, S. M., 1998, Geochemistry of Skarn and Ore Formation. in Dolomites; VSP BV, P.O. Box 346, 3700 AH Zeist, The Netherlands; 300 pp. (Note -also the "References" section of this book for other relevant publications by Aleksandrov and colleagues.) Aleksandrov, S. M. , 2007, Gold Behavior during t=ndogertic and Supergene Alterations of Stalfides in Magnesian Skarns; Geochemistry International, v: 45, no. 2, pp. 152-169, Pleiades Publishing Ltd. (Springer).. Boyle, R. W., 1957, An Occurrence of Native Gold in an Ice tens: Giant Yellowknife Gold Mines, Yellowknife, Northwest Territories; Eccmomic Geology, v.46, pp. 223-227,' Dawson, K. M. and R. V. Kirkham, 1996, Skarn Copper, i n Geology of Canadian Mineral Deposit Types, (ed.) O. R. Eckstrand, W. D. Sinclair, and R. I. Thorpe,. Geological Survey of Canada, Geology of Canada, na 8, pp. 460-476. Dick, L. A., 1980, A Comparative Study of the Geology, Mineralogy, and Conditions of Formation of Contact Metasomatic Mineral Deposits in the Northeastern Canadian Cordillera; Unpublished Ph. D. Thesis, Queen's University, Kingston, Ontario, Canada. Grabber, D. E., 1974, Skarn-Ore .Relationships in a Contact Metasomatic Cu-Fe Deposit, Little Chief Mine, Whitehorse, Yukon Territory; Unpublished M. Sc. Thesis, University of Wisconsin. Harada, K., K. Nakao and K. Nagashima, 1973, Valleriite from Little Chief Mine, Whitehorse copper belt,. Yukon, Canada; Mineralogical Journal, v. 7, No. 2, pp; .221-227: Heon, D. (Compiler), 2004, The.Whitehorse Copper Belt, Yukon:. An Annotated Geology Map; YGS,Open File 2004-15. Kindle, E. D., 1964, Copper and- Iron Resources, Whitehorse Copper Belt, .Yukon. Territory; Geological Survey of Canada, Paper 63-41. Meinert, L. D., 1986, Gold in Skarns of the Whitehorse Copper Belt, Southern Yukon; in Yukon Geology, Vol. 1, Exploration .and Geological Services Division,. Yukon, Indian and Northern Affairs Canada, pp. 19-43. 39 . GMC DAtA REPORT 3~ 4 8 . Page 411127 Morrison,. G., 1976, Granitic_Rocks and .Associated Mineral. beposits of the Whitehorse: Map- Area,. Yukon Territory; GeoL Association of Canada, Annual .Meeting,. Edmonton, Alberta. Morrison,. G. W., _1981, Setting and Origin of Skarn Deposits. in the Whitehorse Copper Belt, Yukon; Unpublished Ph. D: Thesis, University cif Western Ontario,. London: Mowatt, T. C., 1984, A Preliminary. Investigation of Contact Metasomatic Mineralization from the Cassiterite Creek and Brooks Mountain Areas, Western Seward Peninsula, Alaska, with Regard to Unconventional Deposits of Tin; U. S. Department of the Interior, Bureau. of Mines, Open File Report (unpublished). Mowatt, T. C. and U Jansons, 1985, .Preliminary. Investigation of Acid-leachable. Tin Mineralization, Western Seward .Peninsula, Alaska; U. S. Department. of .the Jnterior, Bureau of Mines, Open File Report No. OFR 32-85. Mowatt, T. C: and J. C. Mowatt, 1982, An Investigation of Some Mineralogic, Petrologic, Geochemical and Geological Relationships at the. Arctic Chief Ore Deposit, Whitehorse Copper Belt, Yukon Territory, Canada. (Final-Draft Copy of U. S. Department of the. Interior, Bureau of Mines, Open File Report. "Lost" by the now-defunct USBM.). Petruk, W., D. C. Harris and E. J. Murray,. 1970, An Occurrence of Valleriite .from New Imperial. Mine, Yukon; Canada Dept Energy Mines Resources -Mines Branch, Division Report MS PP 70-1, 6 pP• Ramdohr, P., 1980, The Ore Minerals and Their Lntergrowths (Second Edition, Two .Volumes); Pergamon Press, New York. Tenney, D., 1981, The Whitehorse Copper Belt: Mining, Exploration and. Geology (1967= 1980); Bulletin 1, Geology Section, Yukon .Region, Department of Indian and Northern 'Affairs, Canada. Thompson, R. M. and J. A. Gower, 1954, A Magnesium Borate from Isere, France, and Swift River, .Yukon Territory, with X-ray Powder Data .for Some Anhydrous Borates; American Mineralogist, v. 39, No, 5 and 6, pp. 522-525. Turner, F. J.,1968, Metamorphic Petrology; McGraw-Hill Book Company,.. New York.. Uytenbogaardt, W. and E. A. J. Burke, 1971, Tables for Microscopic Identification of Ore Minerals (Second Revised Edition); Elsevier Scientific. Publishing Company, New York. Watson, P. H., 1984, The Whitehorse Copper Belt. - A Compilation; Exploration -and Geological Services Division -Yukon, ..Indian and Northern Affairs, .Canada, .Open File, 1:25,000 Scale Map with Marginal Notes. Wheeler, J. O., 1961, Whitehorse Map-Area, Yukon .Territory 105 D; Geological Survey of Canada, Memoir 312. Winkler,. H. G. F., 1979, Petrogenesis of Metamorphic Rocks; Springer Verlag, New York (Fifth Edition)... i 40 GMC DATA REPORT 3 4 $ Page 42/227. ISSN 0016-7029, Geochemistry International, 2007, Yol. 45, No. 2, pp. 152-169. ®Pleiades Publishing, Ltd, 2007: Original Russian Tex ®S.M. Aleksandrov 2007, published in Geokhimip4 2007, Nn. 2, pp. 180-19$. 1 Gold Behavior during Endogenic and Supergene Alterations of Sulfides in 1l~Iagnesian Skarns S. M. Aleksandt-ov Uernadsky Institute of Geochemistr~> and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991 Russia Received March 29.-2005 Abstract-The paper presents materials on the genesis of gold deposits of the magnesian-skarn association. It is demonstrated that sulfides are precipitated at these deposits late in the course of the mineral-forming process and often contain visible and fine gold. Post-sulfide mineral-forming processes resulted in the widespread development of hydroxisulfides: tochilinite and valleriite in high-Mg rocks and borate ores affected by serpen- tinization, brucitizatin, and szaibelyitization. The newly formed hydrosulfides inherit gold from the replaced sulfides. The endogenic or supergene decomposition of tochilinite and valleriite in endogenic and supergene; environments stimulates the dissolution of the fine-grained gold and its remobiliiation, first, by hydrothertnal solutions and, subsequently, by meteoric waters. The possibility is discussed of the later regeneration of gold as a consequence of electrochemical processes or at geochemical barriers. The deposition of "newly formed" gold in weathering crusts and placers is discussed, along with the significance of this process for assaying the potential of the weathering crusts and placers. It is emphasized that a significant role in this process is played by cryogenic processes, which can increase gold concentrations in naturally occurring solutions and facilitate its later regeneration. The data presented in this paper are compared with data on gold and PGE deposits of other genetic types, which are hosted in ultramafic rocks and carbonatites, i.e., rocks petrochemically similarto mag- nesian skarns. It is demonstrated that the occurrence of hydroxisulfides in the ores is a significant geochemical and technological problem during the exploration for sulfide ores and their mining and processing. The magne- Sian skarn ores of the deposits discussed in this publication were determined to be a significant source of both primary and placer gold and, perhaps, PGE also. The materials presented in the paper characterize the behavior of gold in the endogenic and supergene processes at magnesian skarn deposits. DOI : 10.1134/5001670290702004 8 INTRODUCTION applied significance for the exploration and revision of skarn mineral deposits. Contact metasomatic mineral de osits local' tzed to p Ma nesian skarns are formed via the metasomatic .magnesian skarns are characterized by a broad spec- g tram of mineral resources: large deposits of iron, boron, transformation of dolomite in contact with. magmatic tin,.. tungsten, beryllium, lithium, base and precious melts.. No calcic skarns develop after dolomites during metals; etc., as .well as economic deposits of sellaite, the prograde stage, and when more mafic and ultrama- fluorite, phlogopite, brucite, nephrite, minerals utilized fit melts are emplaced, skarns at their contacts consist in the ceramic industry and as abrasive materials, gems, of attyssophobe high-temperature minerals (larnite, and coloredstones. Marbles and calciphyres are used in spurri.te, and others). Calcitic rocks and even dolomites cement production. This genetic group of skarn depos- are transformed. during the postmagmatic stage into its still remains, however, poorly examined, as also is talc skates (wollastonite, salite, hedenbergite, and gar- -the potential of these deposits as sources of gold and net types), and rocks with rhodochrosite compose their accompanying PGE. manganoan varieties. The main reason for this is the still inadequate scar- Sulfide ore mineralization is precipitated-late in the city of information on the chemistry and litholo of postmagmatic ore-forming stage and. is typical of all gY types of skarns. This research is centered on magnesian the host carbonate. rocks, which are often combined in skarn gold deposits in eastern Transbaikalia (Zheleznyi .geological. practice under collective names of lime- Kryarh, Bystr-inskoe, and Kultuma ore fields); Aldan .stones or marbles, without determining their Mg con- Shield, Norilsk, and the northwestern Baikal area in .tents, their affiliation with certain types, and the charac- Russia, at the Hol Kol and Suan region deposits in ter of their metasomatic alterations. Consequently, even 'North Korea,. and the Arctic Chief in the Yukon Terri- at thoroughly examined deposits, there is often no clear tory, Canada (the samples of ores and skarns were made classification of their carbonate rocks. with limestone or available for. us by courtesy of T.C. Mowatt of the dolomite, whose distinguishing is a problem of great United States Geological Survey). GMC DATA REPORT. 3 4 8 ls2 Page ,43/127 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS l53 ~ We also used our original. materials, as well as those for example, itt the Asian onion of the Pacific Ore P of other researchers on magnesian sk b arns m Central. Belt. Asia and the Carpathian-Balkan region, which were determined to contain sulfides with gold also. These Compared to normal granites (with 72 wt % SOz), the data. were compared with materials on genetically dis- rocks of the succession granodiorite -- diorite ---- tinct occurrences of precious metals in high-Mg rocks. gabbro contain more mafic minerals (biotite, pyroxene, A feature common forall of these deposits is the devel- amphiboles, and magnetite),. which are able to concen- opmenE of post-sulfide mineralization in the gold ores trace ore elements during .magma crystallization and in the form of hydroxisulfides: tochilinite and valleriite. alterations by postmagmatic-processes, which modify the original compositions of magmatic rocks and can ..produce ore mineralization. - GENESIS AND ZONING OF MAGNESIAN SKARNS Magmas of intermediate basicity, with Si02 concen- The types of skams recognized according to the trattons specified, above, are higher temperature than granites. The data in [16] on the melting temperatures lithological compositions of. the replaced rocks differ of anhydrous magmatic rocks. as -a function of their not only in their mineralogy but also in many other silicity indicate that rocks of intermediate composition genetic aspects. .Because of this; Korzhinskii [1] regarded bimetasomatic andcontact-metasomatic mab e- melt at 1220--1025°C, normative granites melt at approximately 800°C, their leucocratic varieties melt at Sian skams as an individual .petrochemical association, even lower temperatures, and dunites melt at >1300°C which is genetically related to the replacement of dolo- . mites and magnesites, as was proved at numerous deposits Skarns develop in dolomites during. the heating of in Russia, China, and other countries [2-7]. the host rocks under the effect of transmagmatic fluids Pcograde-stage magnesian skams replace~dolomites before the emplacement of the melts. Consequently, at contacts with magmatic melts of various composi- contact skams are formed at temperatures close to those tions (from granites to dunites) [5]. They are character- of magmatic melts; which assimilate dolomite marbles ized by clearly pronounced metasomatic zoning, which that have already been metasomatized. This. is reflected reflects the introduction. of magmatogenic Si, Al, and, to the mineral assemblages of the .rocks and in the partly, Fe. Intrusive rocks and their injections occur in absence of chill zones in the intrusive rocks in contact direct contact with the outer-contact rocks, contain wtth magnesian skarns.at the deposits discussed in this their xenoliths; and were not skarnified during. this .Paper. metasomatic stage. The skams with gold ore mineralization considered The developing metasomatic aureoles have different here are hypabyssal [5], and hence, their metasomatic complicated inner structures, which were controlled by aureoles are characterized by primitive zoning: grano- the P-T parameters under which the hypabyssal skams diorite // fassaite and/or diopstde skarn (+_ spinel) -- developed, from the periclase-free metasomatic facies forsterite calciphyre (± spinel) ---- (±bntcitized peri- to the. gehlenite-merwinite and even spurrite-larnite clase marble) -- dolomtte marble. This'zoning can be facies. The :magmatic replacement mechanisms- of more complicated in contacts with dioritesandgabbro, dolomites are also different: they can be infiltration- with the appearance of zones made up of high-temper- controlled, when the magma near the contact does not ature abyssophobe minerals (periclase marbles and change its composition, ordiffusion-controlled, associ- monticellite skams) [ 17-19j. These magnesian. skams ated with an increase in the basicity of the magma (from ubiquitously contain no quartz-bearing associations, granodiorite to - gabbro) and/or its alkalinity (up to which occasiona!!y occur in the overprinted calcic nepheline Syenite) as a consequence of the assimilation skams and their greisenized varieties. Theskam bodies of the host rocks by the magma [7]. are localized in the contact zones of the intrusions and Existing data on .economic copper. and gold skate marbles and/or form steep veins, stockworks, .and deposits [8, 9] indicate that these deposits are genetically chitntteys up to >400 m long in the latter [5]. related mostly to intrusions of elevated basicity. The Si02 c Sulfide ores, including those with gold, in hypabys- con entrations in grattodiorites and diorites vary from. 59.5 to 49 wt %, and these rocks contain 2.5-5 wt % MgO sal skams are very diverse and are deposited during the , 6:5-11 wt % CaO, 5.8-10.1 wt % Fe,103, 4.8-2.6 wt % posttnagmatic stage, selectively replacing composition- ally diverse metasomatic zones of the contact aureoles NazO, and 2.5--0.6 wt %KZO, respectively. - . . This can be illustrated by the. example of the: Arctic The spatial restriction of gold deposits to the outer .Chief Cu-Au deposit, Yukon Territory, Canada. The contacts of intrusions of this composition is clearly pro- materials on this deposit were provided for us by cour- nounced in the Altai-Sayan region; eastern Transbaika- test' of T.C. Mowatt of the United States Geological Iia, Central Asia [8, 10, 11), Canadian Cordilleras [9, 12, Survey. His collection of ores -and rocks. re resents P I3 ,and the Roc Mountains. in the United States 14 ~ ky [ ~~ ma esian skams from de 't ' ost s to the Whi - ~ P tehorse cop as well as in several other areas around the world where .per belt in the upper reaches of the Yukon River where gold-bearing magnesian skams were found [14, 15], as, , gold placers are also known. GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 AMC DATA REPORT 3.4 8 ~~ Page 44ri2~ i ~ . l 54 ALEKSANDROV ARCTIC CHIEF SKARNS _ the prograde metasomatic stage in dolomites, also AND -0RE MINERALIZATIQN . occur in the periclase marbles and calciphyres. In contrast to magnesian skate deposits in Russia The magnetite ores are. of postmagmatic`genesis, as [l-8 and others], their analogues abroad were studied follows from the selective replacement of the carbonate relatively poorly. Literature data on the Whitehorse belt. constituent of the calciphyres by iron oxides and the are scarce [I2,' 13). It is known that primary lodes preservation of the early." forsterite. The, rhythmically mined in 1967-1982 yielded 10 million tons of ores banded structures of metasomatites and ores were dem- thatcontained 121600 tons of copper, 9.7 tons of silver, onstrated [3, 5, and others] to have been produced by and 7.7 tons of gold. The dumps of underground and the thermodynamically unequilibrated process of do]o- opencast mines (~9 million tons) are thought. to contain mite replacement. According to LR. Prigogine's theory, -1.5 tons of Au, whose contents in the slimes can be as high this is reflected. in the spatial self-organization of the as 250 ppm. These 32 deposits (including minor ore minerals.. A necessary precondition of this. process is occurrences) are under exploration and considered the higher rates of the mineral-forming reactions than promising as prospecting targets far Cu, Au, and Ag. the inflow rates of sndogenic fluids into the skarnified The ore mineralization is hosted in Triassic rocks dorm- dolomites- [3, 5]. Hated by dolomites, whereas the quartzites; arkoses, graywackes, and youngerporphyry dikes are barren [12]. Closer to the intrusion, the mineralogy of the mag- netite ores that replaced the near-contact pyroxene zone ~ The gold contents in sulfides from the Arctic Chief of the aureole changes. The ores there contain variable and related deposits vary [12, 13]. Chalcopyrite from the (uP to significant) amounts of phlogopite, which partly Arctic Chief deposit occurs in association with gold of the or completely replaced the spinet-~iopside skarns. The composition 92.29-88.02 wt % Au, 11.52-7.40 wt % Ag, barren. varieties of the latter are in physical contact with `_ . .and 0.21-0.40 wt % Cu and contains 0.2 wt % Au, and the intrusion. The metasomatic zoning of the Arctic the bomite and chalcosine contain 0.04 wt % Au each. Chief skarns is generally characterized by the inherit- Valleriite, a younger hydroxisulfide; from the North ance of the Mg/Ca ratio in each zone (excluding that of Star deposit contains 0.05 wt % Au, i.e., as much as in magnetite) from the pristine dolomites. The structures the bornite (0.05-0.06 wt %), whereas the chalcopyrite and compositions of all zones correspond to the P-T contains no Au at all [I3]. conditions. of the periciase hypabyssal facies [5]. The deposits of the Whitehorse copperbelt (Arctic The magnesian skams of the.Aretic Chief deposit ~, Chief, Little Chief, North Star, and others) are occur not only at .contacts with the intrusion but also restricted to the western contact of the intrusion and are Found injections of diorite melts into dolomites (Fig. 2). hosted by metasomatically altered. dolomites .(Fig. 1). The rocks .preserve .their zoning and inclusions of In the aureoles of the massif of biotite-hornblende gra- Mg-ludwigite in the forsterite calciphyres .but contain nodiorites and diorites, these rocks are transformed into no magnetite ore mineralization. magnesian skarns, whose genesis and mineralogy are During the postmagmatic stage, the zones of the still known inadequately poorly. Geologists paid much contact aureole of magnesian skarns are replaced by attention, to the composition of the Au- and Ag-bearing Cu ore mineralization [12, 13]. The results of the exam- magnetite ores, newly formed Mg-bearing minerals, including endogenic borates, and, later; calcic associa- ination of skarn and ore samples .from T.C. Mowatt's [ions. The latter developed in the. pyroxE<ne zone in collection (-100. samples) allowed us to partly bridge , intrusive rocks in contact .with the skarns and in the this gap. , vein diorites. The overprinted associations of the pert The dolomites of the Arctic .Chief deposit are. claw marbles consist of brucite pseudomorphs and, in monomineralic and wereprogradely transformed dur- the calciphyres,.of clinohumite, which locally replaces. . ing the magmatic stage into snow-white periclase mar- forsterite, is syngenetic .with the ludwigite;. and con- bles affected by brucitization. Theycomposethe outer fates <25 mot % of the vonsenite end member. The zone of the contact aureole of the granodiorite massif PYroxene zone contains phlogopite and younger saute , whose contact zones consist of hornblende diorites (which bears 15-22 wt % of the hedenbergite end mem- . Closer to the intrusion, marbles give way to a zone of ber [13]), vesuvianite, and tremolite. The calcic skarn forsterite calciphyres with locally occurring boron min- . minerals developing after the intrusive rocks are cling- eralization, which was not found by previous research- zoisite, epidote, and scapolite. Analogous transforma- ers. The Mg-Fe borates are aggregates. of ludwigite tions of the mineralogy of rocks are also typical of the ..crystals. contact zones of many magnesian skarn deposits [5] These rocks give way to magnetite ores. At the - and are commonly identified in the American Iiterature with postmagmatic-stage , calcic skarns proper [23]. boundary with the calciphyres, these .ores contain for- . At deposits in the Whitehorse belt [12, I3] -the latter sterite and show a clearly pronounced .rhythmically ~ . banded structure with repeatedly alternating monomin- , are barren substratiform bodies of saute-garnet compo- sition. They are bimetasomatic in enesis and la eralic bands of forsterite and magnetite. Note. that anal- - g rep ce silicate-bearing dolomite intercalations in the carbo- ogous structures, which were produced already during Hate sequence. GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 6MC DATA REPORT 3 4 8 Pa a 45/I27 9 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS t55 -f- -{- ++ + + + + + _~ Whitehorse: ,... + + + + + + + / 0 200 m / // + j // -~ + -•;. =. -~ -~- i,, j j// Legend ,e,ee + + +/ii ~/ii//+ X102 ++3 4-56 e °e°eeee ~-- -~- ~ j//~ :/// oe°e /// /// / -{-- + ~-- eeeee + /%~~//~~/// :.~.. ~- -~- -F- 2 ///////// ~ . + + ~ -. Whitehorse copper belt + + + -{- -k- j%/ ~j, // / ..Legend. + -}-..~ = /// + ~. -I- // + ®. I Alaska Aktf6aesiRC~ ~" 7ertioxiu _L ~~ Fairbanks /• ~, + --t- // ~ T ~ -~- ~: 0 2 ~ ~ -~ + + // + + + e011 3 ~ t + + + + + + -: T 4 / Yukon Territory '~ ~ . ~ ...F 1. 0 0 ~.Whiteborsc~• T ,eeeee + .+. + / 't \ ~ 000 O O O O PACIFIC ^~. 0 0 0 0 0 0~"~... ~::. . OKEAAt ~~ 0 0 0 0 0 0 . .British Colombia o e o 0 0 0 0 0 0 0 0 0 0 1 2 3lan ~~ eeeeeeeeoeee 0 0 0 0 0 0 0 0 c.o 0 o c. 0 0 0 0 0.0 0 0 0 0 0 0 0 u eee ee eee ee eee ee t t ~. ~. - ~p~ ~ 0 0 0000000000o~oooeeoooooooooe 000 eo 0 0 0 0 0 0 0 0 o e o 0 0 0 Fig. 1. Whitehorse copper belt and the Arctic Chief deposit in the Yukon Territory, Canada [17]. (a) Whitehorse :copper belt. (1) Triassic dolomites; (2) Triassic temgenous rocks; (3) conglomerates; (4) Jurassic intrusive rocks (granodiorites and contact- fades diorites); (S~ Jurassic ska;ns with ore mineralisation; (6) Quaternary basalts. (b) Map and cross section of the Arctic Chief .deposit..<I) Dolomites; (2) quartzites; (3) diorites and granodiorites; (4) skams; (S) orebodies;{6) postmineral porphyry dikes. Min- eral deposits in the proximity of the town of Whitehorse: { 1) Arctic Chief; (2) Little Chief; (3) North Star. GFACHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 - 6MC DATA REPORT 3 4 8 Page 46/127 156 ALEKSANDROV ..s, --- 1~ ~ rs,l l\\,\\ \ ~\\\\ i u\ j ~ s u ~111,ILd il\, \\\\\ \\\.\\\ ~4 ~~,~,,~~~,~ \ ' \ \ ' \ ` ~ , ~ ,i ~\ \ i~FoCa~~~I`\ :r11„\\~`\~,ils,iii`i ~\\ _ * \\~ . 11\ , ll 1 \~ `\\ ` \ \ ' / /'~ _ \ ~ \ 1 ~ 11\ 1\ \ \ I\ t ii 1 \ 1\ i„\ \\\\\\ 11,1\\\\~\\\\~I I\\\\\\ \\\\ /~/i \~ 11 i~ S \ \ \ \ \ \` s \\\ 1 ri/// ~ ~!~i~~i ~l `~\\ \~\~\~ ~~\~~ ~~~~.~ ~` / 4 / /r „ ,,,,/ r,11\ 1 ~, 'Ir/ //,r/ rOrrr~i \' \\1 21\\\\\ :\.'4cm,==- r Fig. 2. Diorite injection in dolomite and zoning in magnesian skams. Arctic Chief deposit (sample of T.C: Mowatt). (1) Diorite replaced by zoisite (Zo); (2) phlogopite-diopside skam (Ph); (3) diopside skarn (Di); (4) rhythmlically banded forsterite calciphyre (FoCa); (5) disseminated crystals of magnesioludwigite (Ld). Magnification 2.5x. Sulfide ore mineralization at the Arctic Chief and SKARNS AND .ORE MINERALIZATION other deposits in the Whitehorse belt is overprinted IN CONTACTS WITH. GRANITES- anio the skams and magnetite ores.. It consists of lean There are still scarce publications dealing with the pyrrhotite disseminations in marbles and calciphyres Qold potential of magnesian skams genetically related and of pocket-disseminated Au-bearing pyrrhotite- io granite intrusions. Available data shed light onto the chalcopyrite and Ag-bearing botnite ores .with chal- compositional features of the skams and the P-T con- cosine mmagnetite bodies. The ores also contain elec- ditions under which the metasomatic zoning developed. tram, native Ag, and subordinate amounts of tennantite, in the exoskarn aureoles and which controlled the origin tetrahedrite, and Co-, Bi-, and Te-bearing minerals. The of certain mineral assemblages that predated the sulfide chalcosine in association with electrum contains up to mineralization and were coeval with it [5, 8, 17-19]. 0.54 wt % Te [12,13].. The ores sometimes contain molyb- denite (T.C. Mowatt, personal communication in 2004). The lowest temperature .types of skams are geneti- cally related to intrusions of leucocratic granites and The younger mineral-forming processes resulted in alaskil:es -into dolomiies. The inner structures of their the replacement of the Mg-bearing minerals by brucite, bodies correspond to the primitive type of metasomatic serpentine, and talc. These processes at the Arctic aureoles with the complete inheritance of the Mg/Ca ratio Chief, Little Chief, and North Star deposits were of each zone from the pristine carbonate rocks. related to the development of valleriite after the gold= Searing sulfide-magnetite ores [13, 20, 2I]. Skams in contacts with granites. are often greis- enized, a feature that is weakly pronounced or is abso- The oxidation zone of the sulfide ores locally con- lately absent in contacts with`more basic intrusions and twins supergene cuprite, malachite, azurite, and iron is mineralogically .accentuated by the occurrence of hydroxides. The position of the Whitehorse-belt in the F-rich minerals (sellaite, fluorite, and fluoborite) that are permafrost zone with acutely continental climate in the associated with Sn and rare-metal (Be and Li) and with - intense physical youngerAu-sulfide ore mineralization [3, 5, 17; 22]. Yukon .Territory caused the more weathering of the rocks and ores than the chemical During the postmagmatic stage, the mineral compo- alterations of their minerals. sition of magnesian skams is modified, and associated It can- be conchrded that the skarn deposits of this... types of magnetite and borate mineralization are mining district in Canada show genetic and mineralog- formed in these rocks, Together with: phlogopite and ical features of their ores and rocks, including the pres- humites. This process is followed by the variably pro- ence of Mg-Fe borates, are similar or analogous to gold nounced replacement of the metasomatites and nearby deposits in Transbaikalia, Aldan Shield, and the.Rus- intrusive rocks by overprinted calcic skams [2, 5,.22, Sian Far East,- which are localized in metasomatically 23]. This replacement can be seen most clearly in the altered dolomite sequences that were intruded by mag- compositional modification of the spinet-pyroxene mas of moderate basicity [5]. Tracing the genetic links zone to contact wish intrusive rocks. The metasomatites of the gold-sulfide ore mineralization in magnesian are transformed into associations of Fe-rich pyroxenes ( skams with magmas of other composition, it seems to (salite), clintonite, tremolite, vesuvianite, andradite- be necessary to consider the setting of the ore mineral- grossular garnet,, zoisite; and even wollastonite; which ization at contacts of dolomites with granites or ultra- are often accompanied. by scheelite mineralization and basic rocks. high-Fe borates (vonsenite and paigeite) [2; 5, 22]. The GEOCHEMISTRY INTERNATIONAL - 'Vol. 45 No: 2 2007 GMC DATA REPORT 3 4 8 _ Page. 47/127 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS 157 near-contact magmatic rocks contain newly formed wollastonite, garnet, epidote, and axinite. The outer zones of the metasomatic aureole (phlogopitized skarns, forsterite- and clinohumite-bearing calciphyres, brucite-periclase marbles, and dolomites with borate mineralization) are preserved. This confirms that the earlier replaced magnesian and newly formed calcic skarns belong to the magnesian assoc~atton. It should be mentioned that magnesian. skarns and their surrounding, carbonate rocks are often "greis- enized" in contact with leucogranites. The F-bearing mineral assemblages are associated with cassiterite and Li-Be ores, which predate the sulfide mineralization. The ores of these deposits .are known to contain not only arsenides and various Cu and Fe sulfides but also -Au and Ag tellurides and economic concentrations of native Au, Ag, and Bi, which are localized in both the skarns. themselves and. their greisenized zones, for instance, mica-fluorite rocks.. . Deposits of this. type in Russia are Lupikko in the Pitkjaranta ore field, -Karelia, Arkinskoe, and other deposits. in the Argun area, eastern Transbaikalia, mag- nesian skarns with ore mineralization in: Khabarovsk region (Vostok II) and the Voznesenskoe ore field in Pri- morye in the Russian Far East. The greisens typically contain cassiterite, Li micas. and Be-bearing minerals, including helvite. Fluorite and sellaite develop (often in economic amounts) in dolomitic marbles. Many of these deposits are accompanied by genetically related gold placers. , Sulfide and gold ore mineralization of greisenized magnesian skarns in contacts with leucogranites is characterized by the following features. According to E.N. Nefedov (personal communication), he found gold grains at Lupikko in the Pitkjaranta ore field, Karelia, in mica-fluorite rocks, in which gold grains are spatially restricted to the cleavage planes of biotite and occur in association with Ni- and Co-bearing loellingite and Bi minerals. The gold inclusions were formed after the arsenide and are rimmed by younger tellurides.. The magnetite ores contain. graphite (?) in association with. Ioellingite, sphalerite, and chalcopyrite and show evi- dence of valleriitization of Cu sulfides (Gerbets I deposit, Pitkjaranta), a process quite usual at deposits of this tYPe• nanuc Cu-Ni posimagmattc vein-disseminated pyr- rhotite and chalcopyrite ore mineralization (Table 1) with PGE, Au, and Ag. Diffusion skam found in the area affiliate with the shallowest depth melilite- .and spurrite-merwinite association [25] and are surrounded by periclase marbles (replacing dolomites) in the. peripheries. These skarns are also accompanied by sul- fide mineralization. 'The magnesian .skarns developing .after dolomite xenoliths in the dunites of the Ioko-Dovyren Massif in _ northwestern Baikal area should also be attributed to the low-depth metasomatic facies [24, 26]. These skarns also show evidence of both infiltration and diffu- sion prograde metasomatism, 'with the former expressed in the transformation of the dolomites into monomineralic forsterite and periclase rocks in contact with dunites [24], and the latter is responsible for the development of a more complicated metasomatic zon- ing in dolomites: dolomite -- periclase marble --- forsterite calciphyre --. zones of abyssophobe skarns. The abyssophobe skarns belong to the monticellite and gehlenite-rnerwinite associations [26, 27]. The adja- cent hybrid melts were characterized by decreasing basicity and crystallized in the form ofplagioclase pert= dotites [24, 26]. Both the skarns .and the ultrabasites of the. Ioko- Dovyren Massif contain. sulfide ore mineralization (pyrrhotite, Co-pentlandite, chalcopyrite, valleriite, and other minerals) accompanied by gold and PGE. This is not the only example of deposits of thistype in Siberia. These deposits are known in Transbaikalia (Chiniiskii and Konder massifs) and elsewhere, .but their gold potential is still.known relatively poorly. PRECIOUS METALS IN THE ORES OF COPPER-NICKEL DEPOSITS AND CARBONATITES Ultramafic rocks. accompanied by Cu-Ni deposits in the Norilsk district, near the town of Monchegorsk, in eastern Siberia, and elsewhere (28, 29] and carbonatites with Au--Cu ore mineralization (Kovdor. in Karelia j30], Loolekop in South Africa [31], Jacupiranga in Brazil [32], and others) are petrochemically compara- ble with magnesian skarns and surrounding them calc- phyres [30, 31] _ .Similarly to .skarns, they. often have rhythmically. banded structures [33], which reflect the thermodynamically unequilibrafed crystallization pro- cesses [3, 5] of carbonatites in hypabyssal environ- menu. Analogously. to skarn deposits, they are character- ized by .the development of ore mineralization.. in a high-Mg environment, similar or identical mineral assemblages and the succession ofpost-sulfide modifi- cations of the mineral composition of the host rocks, including their serpentinization, and the occurrence. of endogenic hydroxisulfides (predomirtantly valleririte [30, 31, 34-38] and, more rarely, tochilitine) in these rocks. SKARNS AND ORE MINERALIZATION IN EXOSKARNS AT ULTRABASITES The highest temperature type of hypabyssal magne- sign skarns develop in dolomites at contacts: with ultra- . mafic intrusions. The inner structures of their aureoles are largely controlled by the types of magmatic replace- ment of the carbonate rocks. For example, at deposits in the Norilsk district, infil- tration. monomineralic :forsterite skarns adjacent to monomineralic periclase rocks developed. at contacts of dolomites and ultrabasites [24]. The skarns bear eco- GEOCHEMISTRY INTERNATIONAL GMC DATA RFP(lRT 3 4 S Vo1.45 No.2 .2007 Page 48/1.27 158 ALEKSANDROV Table 1. Composition (wt %) of sulfides in outer-contact disseminated ore, Norilsk deposit Compo- nent 1 2 3 4 5 6 7 8 9 10 11 S 37.39 37.81 34.45 34.35 34.50 34.73 34.12 34.65 34.86 36.40 33.55 As 0.04 0.04 0.04 0.09 0.00 0:00 0.11 0.06 4.08 0.00 O.Ol' Fe 61.98. 60.43. 30.89 30.67. 30.59. 29.92 29.80 30.21 25.23 2.45 2..16 Cu 0.20 0.06 -33:11 33.63 33.22 34.13 33.88 34.23. 26.83 O.10 1,42 Zn 0.06 0.08 0.06 0.07 0.00 0.00 0.02 0.02 0.00 0.01 0.01 Ni 0.87 0.92 0.09 0.00 0.03 0.03 0.01 0.05 12.21 60.77 62.62 Co 0.18 0.11 -0.00 0.01 0.00 0.04 0.05 0.01 0.15 0.02 0.00 Si 0.06 0.08 0.40 0.23 0.25. 0.29 0.23 0.25 0.02 0.00 0.00 Ca 0.02 0.02 0.34 0.00 0.01 0.01 0.00 0.00 0.01 0.01 0.02 Mg 0.12 0.25. 0.33 0:49 0.43 0.58 0.41. 0.46 0.06 0.07 0.08 Al 0.00 0.02 0.17. 0.07 0.09 ` 0.13 0.08 0.10. 0.00 0.06 0.06 Total 99.92 99.82 99.88 99.62 99.12 99.86 98:71 100.06. .99.45 99:89 99.93 Lauon proponton Fe Ni co Cu ~M ' S 0.935 0.015 o.oo 0.97. 0.95 i.00 .0.992 0.01 o.oo 0.00 0.93 1.00 1.03 0.00 o.oo 0.97 2.00 2.00 .1.02 0.00 o.oo 0.99 .2.01 2.00 1.00 0.00. o.oo 0.99 1.99. 2.00 0.99 .0.00 o.ao 0.99 1.98 2.00 1.00 0:00 o.oo 1.00 2.00 2.00 1.00 0.00 o.oo 1.00 2.00 2.00 0.83 0.38 o.oo 0.78 1.99 2.00 0.04 .0.91 o.oo 0.00 0.95 1.00 0:04 1.00 o.oo 0.02 1.08 L00 Note: (1, 2) Pyn-hotite, (3-8) chalcopyrite, (9) Ni-bearing chalcopyrite, (10, 11) millerite. Microprobe analyses, analyst V.G. Senin, Ver- nadslry lnstitute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. In carbonatites, the former mineral replaces Cu-bearing form of large: nuggets,. which have never been found. in sulfides (mackinawite, pyrrhotite, chalcopyrite, and oth- the primary rocks, whose concentrations of precious ers), while the latter replaces pyrrhotite (author's data). metals are at the Clarke levels. An .example is unique Evidence of analogous processes can be observed in Placers in the Urals and the Konder deposit in Kha- sulfide-bearing metasomatically altered dunites of barovsk region. Mount Jurnbo, Washington, United States, which con- fain Cr-ludwigite mineralization. In these rocks, chal- GENESIS AND COMPOSITION OF SULFIDE ORE copyrite is also. replaced by valleriite Cuo,$ZFet,oyS2 MINERALIZATION 77A10_23)(OH)2 1.6(Mgo 23 [39J. , . The deposition of sulfide ore mineralization takes t t It was mentioned above that dolomites n con act place m skarns dunng the latest postmagmattc stage of "with uitramafic intrusions also contain magnesian the :mineralizing process [2, 5, 22, 28, 40]. Dolomites at skarns. Their sulfide ores commonly .contain Ni, Co, some of these deposits contain anhydrite as a possible intermetallic compounds of PGE, and Au (including source of sulfur. This does not rule out the significant native Au). role. of magmatic sulfur, as also follows from its isoto- These facts testify that the ore. deposition processes plc composition in sulfides from these deposits [SJ: ~ in ultramafics and carbonatites. and Their subsequent The ore minerals` are S-undersaturated pyrrhotite, h drothermal alterattons are eochemtcall com ara- y g Y P arseno 'te or 1~ it 'te pyn .Joel mg e, chalcopyn , cubantte, and ble with analogous processes in magnesian skarns. This bornite at subordinate amounts of Fe, Cu, Zn, Ag, Bi, also pertains to the endogenic and supergene transfor- Sn, Te, and Se sulfides containing Au in the form of an orations of minerals containing precious metals in these isomorphic. admixture and as a native .metal. The ores rocks. contain younger As and Sb sulfosalts [4; 22, 28, 413] Supergene-processes responsible for the migration and native Ag and Bi. Pyrite is rare but is occasionally and possible regeneration of gold and PGE dunng the contained in the marbles and overprinted calcic skarns denudation of hyperbasites, phoscorites, and carbon- ( in the outer and inner contact zones. atites are still known relatively poorly. These metals are Sulfides of Fe (pyrrhotite and more rare troilite and known to occasionally occur in placers, often in the mackinawite) and Cu (chalcopyrite, bornite, cubanite, GEOCHEMISTRY 1NTERNATIONAL Vol. 45 No.2 2007 GMC DATA REPORT 3 4 8 _ Rage 49/127 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS 1.59 and others) are typomorphic of all zones of the magne- Sphalerite often'is barren of gold, but marmatite Sian skarn bodies and often replace earlier magnetite.. contains 0.06 wt % gold when occurring in ludwigite Loellingite and arsenopyrite additionally ..replace ores at the Titovskode deposit and 0.05 wt % gold at the Fe-Mg boraces of the ludwigite and paigeite series [28] Ba~ita Bihor deposit, Banat, Romania. _This rs likely or are contained as disseminations and pockets in phio- caused by the occurrence of 2 wt % Cu in ZnS in the gopite and in pyroxene (salite), tremolite, vesuvianite, form of emulsion chalcopyrite dissemination, and garnet skarns. Other sulfides, sulfosalts, and native chalcopyrite contains. variable Au concentrations, metals are disseminated in all of the metasomatic rocks which are. sometimes as high as 0.25 wt % in greis- or compose stringers in them. The highest concentra- enized skarns with aikinite, bornite, and Bi-bearing lions of Bi minerals were found in overprinted calcic minerals at the Karadjhal deposit. in the Digilenskie skarns, for example, at the Ho] Kol deposit in North Mountains, in Kazakhstan. Low Au concentrations {no Korea [2, 5, 22,40, 42,.44]. more than 0.04 wt %) were detected in chalcopyrite Literature on gold deposits of various genesis con- lain information on the occurrence of Co, Ni, and PGM from valleriitized borate ores from the Zapadnoe deposit in the Bystrinskoe ore field, eastem Transbaika- in sulfide ores. Gold and PGE coexist in mineralized lia, and O.OI wt % in sulfide-bearing calciphyres of the magnesian skarns in Siberia (Gornaya Shoriya, Norilsk Lebedinoe deposit in the Aldan Shield_ mining district, northwestern Baikal area, Transbaika- chalcopyrite rn the. ores from calciphyres of the. lia, and Khabarovsk krai) [5, 28, 43, 45] in Russia and, Baits Bihor deposit in Banat, Romania, contains 0.02- in Europe; atthe Banat, Romania; Rhodope Mountains, O.1S and 0.30 wt % Au, whereas this mineral from sul- Bulgaria; and elsewhere [41, 46]: fide-bearing spinel-fassaite skarns of the Traversella deposit, Italy, contains no more than 0,05 wt %. Gold (up to 0.10-0.22 wt %) was. detected in .chalcopyrite GOLD IN ARSENIDES AND SULFIDES from the ludwigite-bearing calciphyres of the Grizzly Our- data on the gold potential of sulfide ores at Gulch, Little Cottonwood Canyon, Utah, in which chal- copyrite is` associated with pyrrhotite and Ag- and Bi- many magnesian skarn deposits both in Russia :and . elsewhere (28] make it possible to identify the occur- bearing minerals and is replaced by valleriite. Gold (0.02-0.07 wt %) is contained in chalcopyrite from the. rence modes of precious metals in them. The Loellingite su.anite-ludwigite ores of Blind Mountain, .Nevada [28]. contains variable amounts of Au, up to 0:24 wt % at the Thrs mineral from the $essie and Maple .occurrence, ~. Titovskoe borate deposit in the Cherskii Range and . Alaska, contains variable Au concentra- Lost River 0.33. wt % Au in the greisenized skarns of the Lost Alaska, United States. At other deposits, River Mine , lions, from 0.05 to 0.17 and even 038 wt %. , Au concentrations are .about 0.04 wt % or below the Pyrite from the Taror skarns contains 0.04--0.09 wt % Au, detection limit of microprobe analysis. Arsenopyrite and this mineral from Gijhdarva, Tajikistan, bears more from paigeite ores from the Moral' nyi Prospect of the thane 0.08-0.32. wt % Au. Analogous gold concentra- Titovskoe deposit contains OA8-0.31 wt % Au, and lions were found in iron disulfide contained in calci- kotoite-bearing calciphyres of the Baits Bihor deposit phyres from the Lebedinoe deposit. High Au contents in Romania, which also bear tellurides, contain up to (0.18-0.23 wt %) .were detected in pyrite. from Ludwig- 0.11 wt % Au. Arsenopyrite in sulfide ores from the ite-magnetite ores of the Chingatai deposit in eastem Serdtse-Kamen' deposit in Chukotka was determined Transbakalia. Pyrite from Grizzly Gulch, Little Cot- to bear up to 0.25% Au. tonwood Canyon, Utah, contains 0.19 wt % Au;, and this mineral from the Bessie and Maple occurrence, Iron sulfides can also contain gold.. For example, Lost River, contains 0.42 wt % Au Pyrite from the Hol troilite in sakhaite rocks from the Dokuchan deposit in Kol deposit in Korea bears 0.36 wt % Au. the Cherskii Range contain 0.12 wt % Au. More wide- spread pyrrhotite from the ludwigite-bearing caici- Younger Cu-bearing sulfides also .contain Au. For phyres of the Lebedinoe deposit in the Aldan Shield example, chalcosine from harkerite rocks of Camas and the analogous values 12 wt %Au 04-0 contains 0 N[alag, Skye Isle, Scotland, contains 0:12 wt % Au, and , . . are .0.06-0.20 wt % for the. ludwigite ores of the the accompanying bornite contains 0.05-0.08 wt %Au; Gol'tsovoe deposit,. Cherskii Range, 0.06-0.10 wt % Lead sulfide also contain gold and, often, also silver. .for the Krumovo deposit in Bulgaria, 0.15 wt % for the Galena from sulfide ores of the Serdtse-Kamen' deposit sulfide-ludwigite ores of Mount Brooks, and 0.08 wt % in the Chukot Peninsula bears up to 0.12 wt % Au. This for the Bessie and Maple occurrence in the Lost River ore mineral contains 0.09 wt % Au when occumng in gre- field in Alaska. Pyrrhotite in ludwigite-magnetite ores isenized skarns of the Karadjhal deposit in Kazakhstan, from the Dokuchan deposit contain 0.02-0.10 wt % Au. 0.05-4.17 wt %Au in calciphyres of Baits Bihor, Roma- Diopside skarn in Gijhdarva, Tajikistan, contains pyr- nia, 0.05 wt %Au in Skye Isle, Scotland, 0.15 wt % imthe i rhotite with 0.12-0:16 wt % Au, and this. n-uneral con- Iv[ount Brooks skarns, and 0.1 I wt % at the Bessie and tams 0.07-0.1 wt % Au at the nearby Taror deposit and N[aple occurrence in Alaska. Boulangerite from kotoite 0.02=0.11 wt % Au in the. ludwigite-kotoite marbles at ' marbles from Baits Bihor contains up to 0.21 wt % Au, !~ Hol Kol, Suan, North Korea: and tetrahedrite from the HoI Kol deposit, Korea, bears I~, OEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 AMC DATA REPORT 3 4 8 Page 50/127 .160 ALEKSAND120V 0.29-0.33 wt % Au. Molybdenite from.. this deposit of meters thick. The dolomites are replaced by contains variable Au concentrations, from 0.03 to 0.19 hypabyssal skarns, calciphyres, and overprinted calcic and even 0.45 wt %. sk3rns. Their sulfide ore mineralization corresponds to The data' presented above on the gold-bearing suI- the types of Cu-Ni pyrrhotite-chaIcopyrite-pentIandite fides were obtained by examining .hand-specimens of ores with cubanite known at the Norilsk I, Talnakh, and boron-bearing calciphyres, ludwigite and. magnetite Oktyabr'skoe deposits. The ores ubiquitously contain ores, and magnesian skates from the author's collection vallenite (0.5-5 vol %) and precious metals: PGE (Pt (5, 28, 40, 47J. This study was not associated with the , Pd, and others), Au, and Ag [33]. systematic sampling of the orebodies, and the results The ore mineralization in the outercontact zones is presented here should be considered provisional .and hosted in btucite rocks (pytrhotite, pyrite, and magne- can be taken into account when the gold potential of the tite), setpentinized magnesian skarns (Table 1) ealci- sulfide ores of these and other skarn deposits is assayed. , h res a p y nd calctc skarns (pyrrhottte, pentIandite, chal- Literature data indicate that sulfides (except their copyrite, and millerite). These stringer-disseminated Ag-, Bi-, and Te-bearing species) contain almost no iso- outer-contact ores pervasively contain PGE (0.5-7 ppm Pt, morphous Au. Conversely, micrometer-sized to visible 1-35 ppm Pd, and 0.01-0.21 ppm Rh), Au (0.01- inclusions of native gold occur at dislocations of their l0 gpm), and Ag (0.77-17.6 ppm) [37]. crystals and in the intergranular space [4], as was con- firmed by the results of this research Gold also forms The highest valleriite concentrations were found at . veinlets in skams and marbles, for example, at the Hol the Talnakh (up to 15 vol %) and Oktyabr'skoe (up to 9.5 vol %) deposits (data of V.M. Isoitko 1978 [37]) Kol deposit in North Korea, thus reflecting gold migra- tion and redeposition by hydrothermal solutions , . 'I'bis provided grounds to distinguish millerite pyrrhotite- . valleriite ores as an individual type, which contains 5-7 vol The data presented above on gold concentrations in % hydroxisulfide. This mineral was also found in the magnesian skarns and the contact zones of leucogran- mineralized serpentinites and brucitites. Valleriite and ites and alaskites that were intensely greisenized with tochilinite are formed during the post-sulfide stage (see the development of fluorite and F-bearing. silicates " below) of the hydrothermal process, simultaneously. norber te hlo o ite and Li-micas and - ( ~ p g p ) the over - with stgmficant transformations of the mineralogy of printing of sulfides and tellurides indicate that this mag- the gold-bearing ores.. nesian-skarn type of gold mineralization deserves more detailed examination. This also follows from the find of Au (2 ppm), Ag (5 ppm), and Pt (0.5-ppm) in rhythmi- POST SULFIDE MINERAL-FORMING (_ cally banded fluorite metasomatites of the Voznesen- PROCESSES skoe ore field in the Russian Far East [11], which con- tams Be ores Sulfide ores in magnesian skarns and other rocks of . The materials presented above imply that skarns similar etrochemical com osit" n p p to (ultrabasites and carbonatites) typically contain mixed-layer hydroxisul- having various mineral composition and affiliating with fides, such as tochilinite, vallerii e, and more rare haa- different facies are favorable for the deposition of sul- palaite ((Feis6Nio.?4)SZ 1.61(Mg0.84Fe0.16)(OH)2 and fides with gold. Their concentrations. can be .mined from the orebodies and related placers, as is currently yushkinite Vi_.YS (Mg,AI)(OH)2) [28, 40,.41, 44J. They. re Iace sulfides and/or ma ' nesioludw' ' P g t rte 2 28 g ( done at some deposits or can be considered for future > 40) and are syngenetic with the serpentinization of Mg developrneni with the application of more advanced .silicates and, what is important;. are coupled with the technologies of the recovery of precious metals. brucitization of skarn minerals, .including Mg oxides Magnesian skarns at contacts with ultramafic intru- and carbonates, and the szaibelyitization of Mg and sloes also contain sulfides. The hypabyssal spine]- Mgr-Fe borates [28, 40J. Many. magnesian-skarn gold monticellite (±perovskite, melili[e, and merwinite) deposits at contacts withgranitoids, as well as copper- skarns that replaced dolomite xenoliths in dunites in the nickel deposits related to ultrabasites and carbonatites, Ioko-Dovyren Massif, northwestern Baikal area, were ubiquitously contain tochilinite 2FeS • 1.67(Mg; Fee+; determined to contain Co-pentIandife (38.57 wt % Co, Al)(OH)2 and, more often, valleriite CuFeSz • n(Mg, Fe, 9.63 wt % Ni), mackinawite (9.7-10.6 wt % Co),,troi- Al)(OH)Z (Table 2). Their composition reflects both the liter galena, clausthalite, native gold, silver, and tin, and position of these minerals in the mineralogical system- ', valIeriite [26]. This. is consistent with the composition atics and the occurrence of Mg(OH}2, Fe(OH)2, of the sulfide ore mineralization in the hyperbasites, Mn(OH)2, Al(OH)3, and other components in the oxide which contain troilite-pyrrhotite ores with pentIandite; group of these minerals [28, 34-36, 38, 40]. chalcopyrite, and cubantte that contain unevenly dis- tributed PGE and Av. For example the anorthosites of this Valleriite and, later, also tocilinite were first found , massif contain 4.1 ppm Pt, 7.8 ppm Pd, and 3.2 ppm Au, in Cu-Ni ores genetically related to ultrabasites, in which hydroxisulfides are often rock-forming minerals whereas the Cu-Ni ores in dunites are richer in Pd [26]. . Laputina [34) and other researchers (29, 35, 36) have The metasomatic aureoles in marbles around hyper- demonstrated that these minerals actively replace vari- basite intnasions in the Norilsk mining district are tens ous types of sulfide ores, predominantly pyrrhotite, GEOCHEivt1STRY WTERNATIONAL Vol. 45 No.2 2007 AMC DATA REPORT 3 4 8 Page 5/127 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS 161 Table 2. Composition of tochilinite and valleriite: n(Fe,Cu)~ _zS~ • nt((Mg, Fe)(OH)Z + Ai(OH)3]" Deposit Fe Cu EM n ' S Ma(OI-I)2 Fe(OH)2 Al(OH)3 E m Tochilinite Zheleznyi Kryazh, Transbaikalia* 1.95 0.05 :2.00 2 0.85 0.00 0.i5 1.51 1.93 0.01: 1.94 2 0.86 0.05 0.09 1.49. Titovskoe NE Russia* 1.80 0.14. 1.94 2 0.54 0.23 0.23 1:53 Same* (replacing troilite) 2.00 0.00 2.00 2 .0.88 0.01 0.11 1.38. Same* (replacing pyrrhotite) 1.98. 0.00 1.98 2 0.84 O.I I 0.05 1.40 Gavasai, Kyrgyzstan* 1.86 0.00 7.86 2 0.00 1.00 ? 1.47 Kamaisi, Japan [34J 1.34 0.34. 1.68 2 0.78 0.00 0.22 1.67 1.26 0.48 1.74 2 0.79 0.00 0.21 1.65 Pensilvania, United States [38) 1.62 0.00 1..62 2 :0.79 ` 0.00 0.21 1.79 ` Jacupiranga, Brazil {C) (32) 1.78 0.00 1.78 2 0.39 0.31 0.30 1.67 Valleriite Zapadnoe, Transbaikalia* 1.12 0.88 2.00 2 0.77 0.23. 0.00: .1.33 1.37 0.63 2.00 2 0.96 0.00 0.04 1.08.. _ 1.34 - 0.66 2.00 2 0.94 0.00 0.06. 1.16 1.56 0.38 1.94 2 0.91 0.00 0.09.. 1.47 a a Kultuma, Transba . 0.90 1.01 2.00 2 0.88 0.12 O.oo 1.63 C Baita Bihor, Romania* 0.93 1.07 2.00. 2 0.86 0.14 ? 1.67 Hol Kol; North Korea* 0.98. 1.02 2.00 2 0.85 :0.06 0.09 1.24 0.92 1.08- 2.00. 2 0.87 0.02 0.11 1.35 Grizzly Gulch, Utah, United States* 0.99 .1.01 2.00 2 :0.80 0.00 0.20 1.80 Little Chief, Yukon, Canada [21] 0.81 1.19 2.00 2 0.71 0.06 0.23 1.64 0.80 1.20 2.00 2 0.73 0.21 0.06 1.67 1.07 0.93 2.00 2 0.68 0.00 0.32 1.53 North Staz, Yukon, Canada [13J 0.80 1.20 2.00 2 ? 0.12 ? - Kaveltorp, Sweden [38] 1.16 0.84 2.00 2 0.73 0.00 0.27_ 1.30 Norilsk, Siberia [34) 0.95 1.05. 2.00 2 0.86 0.14 - 1.51 ** 61 1 0.39 2.00 2.2 0.05 - 034. 1.65 Same . Kovdor, Karelia (C) [30] 1.18 0.82 2.00 2 0.79 - 0.21 1.61 Same (C) 1.47 0.53 2.00 2 0.78 - 0.22 1.63 Loolekop, South Africa (C) [38] 1.03 0.95 T.98 2 0.73 0:00 0.27 1.57 Same (F) [38J 1.02 0.98 2.00 2 .0.65 0.34 - 1.70. l AS 0.95 2.00 2 0.76 0.22. 0.02 1.66 0.96 1:04 2:00 2 0.75 0.16 0.09. 1.67 Jumbo, Washington, United States *(D) 1.09 0.82 1.91 2.1 0.77. 0.00 0.23 1.60 l nesian skarns and calciphyres according to * i our [28, 39, 40, 44, and others) and literature data, including ng mag Note: From sulfide-bear carbonatites (C); phoscorites (F), arin b lfid and dunites (D). **Val leriite with 6 1 mol % Ca (OI~2 in its g e- e hydrozisulfides from su oxide constituent. GEOCHEMISTRY INTERNATIONIAL Vol. 45 No. 2 2007 Pdge 52/127 /!IAA nn-rn ~rnnn-r z ~ o 96 1.04 2.00 2 0.90 0.10 0.00. 1.64 * 0 li ik 162 ALEKSANDROV Japan. I. Kusachi found this mineral in association with loellingite, arsenopyrite, chalcopyrite, cubanite, pyr- ~ other sulfides (L Kusachi, per- . rhotite, witticherite, and . sonal communication on August 27,1998). We .established [28, 40; 43, 44j that valleriite and- tochilinife are also typomorphic post-sulfide minerals at gold. deposits of the magnesian skarn ore association.- This significantly expands our knowledge of the occur- rence of hydroxisulfides in various genetic types of sul- fide ores (Table 2). The genetic role of the replacement of Fe and Cu sulfides by hydroxisulfides in the ertdogenic and super- Irene geochemistry of Au and PGE is still poorly under- stood [28, 39, 40, 43, 44]. The significance of the prob- lem of the tochilinization and valleriitizatin of sulfides in serpentinized ultramafic rocks related to the genesis of Cu-Ni ores with PGE and Au was first highlighted. Fig. 3. Outer-contact stringer~lisseminated copper-nickel by the data obtained by Ramdohr [37] and Other researchers Of these mineralS {34-36, 38]. ores, Norilsk. Valleriite (Va) surrounds chalcopynte (Cp) in skarns (Sk). Magnification 2x. Tochilinite and valleriite have a low hardness and are ductile and layered, i.e., possess characteristics. Cu-Ni, and containing magnesian minerals ones, at the hampering the identification of these minerals. In asso- elation with pyrrhotite, chalcopyrite, and other sulfides, Norilsk group of deposits. The hydroxisulfides have these minerals are commonly misidentified as graphite variable compositions (Table 2) of their sulfide and . based on their optical characteristics. In the ores of Cu- hydroxide constituents at significant .structural differ- Ni skarn deposits, valleriite and tochilinite develop ences between them [35]. along the grain boundaries of sulfides and rim sulfide It was established [34] that valleriite of the Norilsk grains (Fig. 3). When these -ores .are technologically deposits contains 7-16 wt % Cu in pentlandite-chal- processed (crushed and floated), it is practically impos- copyrite-pyrrhotite ores and 17-22% Cu in the miller- sible to get rid of hydroxisulfides; and thus, the techno- ite-bornite-chalcopyrite and pentlandite-chalcopyrite logical concentrating process of these ores is associated ores. The pentlandite-pyrrhotite ores with subordinate with significant losses not only of Cu but also of pre- . amounts (3-5 vol %) of chalcopyrite contain mostly cious metals [31, 48]. tochilinite. As was recently demonstrated in [2, 28, 40, 44], The composition of the hydroxyl. constituent of when replacing Au-bearing sulfides, Fe and Cu hydrox- hydroxisulfides is controlled by the composition of the isulfides inherit their Au in the form of fine-grained. native silicates, first of all, serpentinized forsterite and iron metal. For example, tochilinite from Zheleznyi Kryazh, oxides, including magnomagnetite. They are contained Transbaikalia, contains 0.01-0.4 wt % Au; and valleriite in both the magmatic rocks and the adjacent metasoma- from the Zapadnce .deposit contains 0.05-0.15 wt % Au tiles that replace dolomite and often contain anhydrite. (the chalcopyrite contains 0.04 wt %a Au). These concentra- The valleriite of these associations commonly contains lions are comparable with those published for deposits in Mg (11-12 wt %), whereas the tochilinite .bears. up to the Whitehorse belt in Canada. 14 wt % Mg. In the process of endogenic and supergene alter- Hydroxisulfides of other composition (Table 2) ations, minute gold particles contained in hydroxisul- occur less frequently at the Norilsk deposits. The mas- fides are dissolved more easily than large gold. grains sive chalcopyrite, cubanite, and talnakhite ores contain (because of the greater specific .surface. of smaller newt formed Mg-free valleriite of` the composition. Y 'tionall fa ' i b the grains). This process is addt y cil tested y CuFeS2 • nFe(OH}2, and tochilinite of the composition general chemical instability of tochilinite and valleriite 2Fe~ _ ~S • nFe(OH)2 replaces troilite and hexagonal pyr- in surface environments. These minerals are. replaced otite in the monticellite skarn. The melilite-merwin-: rh ase of dissolvable M Fe by magnetite wtth the rele g, , ite skarns were determined to contain high-Ca valleriite and Cu sulfates. The latter, in turn, create favorable CuFeS2 • n[(Ca,AI)(OHh], which replaces cubanite and conditions for gold migration in acid hydrothermal pyrrhotite. The. sulfides have variable Cu concentra- solutions and its redeposition when conditions change, lions, fromll to 3~.5 wt % [35]. for example, at geochemical barriers (as at reactions... ~ Valleriite- (whose composition was not determined) with carbonates). Evidence of this process is the devel- was also found in gehlenite-spurrite skams of shallow- opment of thin veinlets of native gold along cleavage. depth facies at the Fuka .deposit; Okayama Prefecture, planes of calcite in marbles; for example, at the Hol Kol GEOCHEMISTRY INTERNATIONAL'.: Vol. 45 No. 2 2007 ''~ 6MC DATA REPORT 3 4 8 ~, Page 53/127. GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS 163 borate magnesian-skarn deposit, the largest in North Zheleznyi Kryazhand at the Zapadnoe deposit in the Korea (author's data). At thin deposit, gold-bearing h th marbles occur .near chalcopyrite-magnesioludwigite ores, which are replaced by valleriite [28, 40, 44]. Eastern Transbaikalia (at the Bystrinskoe, Kol- tuminskoe, Zheleznyi Kryazh, Arkinskoe, and many.. other deposits in the Argun-Gazimur divide), Aldan Shield (Lebedinoe and -other deposits), and the Yukon Territory in Canada (Whitehorse copper belt) contain economic gold-bearing :alluvial placer deposits. Their genesis was predetermined by the denudation of pri- mary magnesian skarn deposits with gold-bearing sul- fides and provide evidence of their significant role as a source of placer gold. The gold potential of these deposits is still not depleted. For example,.it is thought that mineralized skams in the Bystrinskoe field contain 0.6 ppm Au and 1.S% Cu at predicted reserves as large as i30 tons of Au, 4 mi}- lion tons of Cu, and 93000 tons of Ag [11]. Placers at .the Bystrinskii group of deposits ubiquitously contain scheelite, which was mined in the Bystraya and Il'dikan river valleys in the 1940s. The sources of the valuable minerals of these placers were the Zapadnoe (Fig. 4), Vostochnoe, Malyi Mednyi Chainik; and outer deposits of magnesioludwigite ores with pocket and dissemi- nated pyrrhotite-chalcopyrite ore mineralization that is extensively replaced by valleriite during the serpentine- zation of the forsterite skams and calciphyres and the replacement of the borate ores by szaibelyite [2, S, 28, 40]. Although the. black-sand panning samples contain no preserved minerals of magnesian skams other than magnomagnetite, these samples contain garnet. and,. near primary deposits, also pyroxenes, scheelite, and. gold (905-976 fineness) [28]. When.these placers were washed for gold by small diggers, the first priority tar- gets were sands with magnetite and scheelite as those richest in gold. The Zheieznyi Kryazh sulfide-bearing ores and, par- ticularly, the pyrrhotite-bearing borate ores of the Rud- nichnayabody are also significantly replaced by tochi- linite and valleriite (Fig. S) [2, 28; 40]. The: ludwigite and magnetite. ores. are localized in magnesian skams that developed in dolomites of the Bystrinskaya Forma- tion of Paleozoic age. They contain up to 29% fine (no larger than 0.07 mm) and coarser grained (up to 1 mm) gold; as well as lumpy and amoeba-shaped unrounded gold grains in aggregates .with chalcopyrite.; The denu- dation of the orebodies of the deposit gave rise to related alluvial gold placers in the valley. In the oxidation zone, sulfides and hydroxisulfides are supergeneously replaced by Fe and Cu hydroxides, which can adsorb Au and release it under the effect of sulfate- and thiosulfate-bearing groundwaters. This can be exemplified by deposits in eastern Transbaikalia, whose tochilinite- and valleriite-bearing ores are trans- formed into magnetite sands loosely cemented with calcite. We identified such newly formed rocks at the Bystrtnskoe ore field. At the latter, t ey occur m e most deeply. eroded orebodies in the southern flank. of the deposit At many. other skarn deposits,. hydroxisulfides .are completely oxidized but still can be identified in super- geously unaltered ores [28, 40; 43]. For example, the supergene alteration products of .chalcopyrite that has been replaced by valleriite (Table 2) in the ludwigite-' bearing calciphyres at Grizzly Gulch in Utah .are iron hydroxides and malachite with 0.19-0.52% fine gold. A similar situation occurs at the Kultuma ore field on the Gazimur River, but the predominant primary sul- fide of the boron-bearing skams and calciphyres is chalcopyrite, which is partly replaced by valleriite [43]. Gold-bearing placers in the valley were mined for more than one century (until 1958) and were thereby repeat- edly rewashed. Genetically ..analogous placers promising fore gold and cassiterite are widespread along some tri-butanes of .the Argun in the Bogdatsk-Arkia mining district in Transbaikalia. 't`hese placers are genetically related to sulfide-bearing magnesian skams with magnetite, cas- siterite, beryllium, and bismuth ore mineralization at contacts with leucogranites [11]. In the Aldan district in Siberia, gold is produced by the long-term development of the Lebedinoe deposit, which is hosted in skamified dolomites intruded by Mesozoic syenites [49]. In addition of sulfide ore min- eralization of chalcopyrite, pyrrhotite, and pyrite -with subordinate amounts of galena, Bi-bearing minerals, sulfosalts, and tellurides, including calaverite, the mar- bles contain native gold and disseminated magnesi- oludwigite and szaibelyite. Our data indicate that the latter minerals sometimes contain valleriite. Along with primary deposits, gold was extracted in this area for more than SO yr from alluvial placers. The reserves of the ore mineralization are comparable with that at the Hol Kol deposit in North Korea: Recently other gold- bearing. skarn deposits (Samolazovskoe and others) were found in this area, and this confirms that the area is promising for exploration for gold. "NEW" GOLD IN PLACERS AND WEATHERING CRUSTS The data presented above on the spatial relation of .gold placers to its primary deposits call for the analysis of gold geochemistry in supergene environments. In spite of inconsistencies iq literature data on the possible scale of supergene :gold migration with groundwaters, the possibility of the s process is taken for granted and is generally not questioned any more. This is directly related to the applied aspect of this problem, namely, the possibility of the origin of supergene. "new" gold as a consequence of its remobilization and, what is GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 GNIC ,DATA RFPnRT 3 d R Page 54/127 164 ALEKSANI~ROV V . _. . .. -f- jjI -}- +' ..... ~~ -1- ~- + + + -{- } + -4- + + + 3 4 + ~. + + ~:~ -~ + + + -}- + + t ._ ~ . -i- + - ~- + -4- + } 5 + + + + + 6 IV + + ~ + + + = + + + o so t, -~- -~- + m + ~~ + + I -}- + -+" + .~: + V +, + VI 7 } g VI V -E- + -~ + ~- + + + -~' + -~ + 2 + 4 + + ; + + + + ~. ~- + + -}- + + + + + 5 3 } + } + ~ + + -i- + -{- + ~+ '+ + + + + VI'. -}- + + + + + -F- ~ ~- + + + + + + + + + -1- -}- + + + + + + -~ _ + + + p + 100 + + }++ + + + + + Fig. 4. Map of the Zapadnoe deposit, eastern Transbaikalia and profiles across this deposit. (a) Schematic map of the Zapadnoe deposit, eastern Transbaikalia. (1) Hercynian granodiorites; (2) pyroxene skams; (3) forsterite skarns; (4) ludwigite-magnetite ores. (III-VI) Exploration-profile, (b) and{c) Geological profiles across the deposit. (1-3) same as in Fig. 4a; (4) boron-bearing magnetite ores; (s) monominerahc ludwigite ores; (6) postmineral dikes of Mesozoic porphyries;. (7) supergeneously altered ludwigite ores; (S) exploration boreholes. particularly important, regeneration when gold-bearing sometimes provokes doubt. This is .related, -first of all, ed. to the still poorly understood geochemistry of super- . d lacers are form an is weatherin crus g p gene gold regeneration. Facts confirming the. occurrence of newly formed gold in placers and weathering crusts are numerous, but The. data of Petrovskaya [49], Nikolaeva [50], ( the role of this phenomenon in the precipitation of eco- Yablokova [51], Novgorodova et al. [52], and many nomic gold concentrations -was .not .quantified and other researchers indicate that-gold migration and rede- GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 GMC DATA REPORT 3 4 $ Page 55/127 165 GOLD BEHAVIOR DURING ENDOGENIC AND SUPERGENE ALTERATIONS -S position in supergene environments does take place. It '• `~ •.J •' was definitely demonstrated that newly formed super- , ~ ~ ;.~; gene gold occurs as thin films, flakes, dendrites, glob- ~~ , ides, and small. crystals. It is believed that gold is trans- ~ • ~ ~~'' . ~ _ .ported in both solutions and colloids. y~ The morphology and texture of supergene gold were _ -a+ ~, r ~ ., analyzed by Petrovskaya [49]. It was established that ~ ~ newly formed gold occurs at several placers in the area ~~~•' ~' ~ `~- ~ , along the Lena River in Siberia in the form of spongy - ~-~ J k~ ~Mg~d ~ ~ . crusts and humps at the surface of gold grains or ~ ~ ~~,,y : , ~~.•. cement these grains. Other researchers confirmed and ;. ~ : , - ~' A ~;,"• specified these observations. . ~ , , ~Y; •~ According to Nikolaeva [50], newly formed gold °' ~~'^ ~ ~4 , Po was deposited (as humps and crystals) on pale yellow to To tin-white silver-bearing rounded gold grains. of low `-~"" _~=_ fineness. It was found in placers that were produced by ~ . the destruction of .rocks that had Contained sulfides Fig. 5. Pseudomorphic replacement of magnesioludwigite (pyrrhotite and pyrite with .inclusions of low-fineness crystals (Ld, dark gray) by tochilinite (To, black) and of pyr- gold 0.01-~ mm across). At the. same time, gold was gray~eZhelez yllKryaih depose~Polished setction magn fie never found in placers produced by the erosion of gold- cation 30". bearing quartz veins. Newly formed gold was found in placers in the Aldan Shield by Yablokova [51], who determined that particles. Ag and Cu, which are more electrically nega- rounded coarse-grained gold in these placers is 900 to five metals, occur much more rarely in placers. It is thus 923 fine, whereas the newly formed gold is 794-880 commonly believed that the margins of gold particles fine and clearly differs from the primary gold in texture. .should not become enriched in silver and copper when Overgrowths. of newly formed gold on the primary one newly formed gold is precipitated on these particles. are fine-grained, polyhedral, and twinned. It, is known that the margins of gold particles some- ( According to Novgorodova et al. [52], newly formed times have a higher fineness of the gold. The higher gold occurs in weathering crusts in Orenburg Oblast as fineness of gold particles in the margins is sometimes ungeometrieal lumps, angular fragments, and spongy believed j49 and. others] to be caused by the partial masses of dull brownish and red-brownish color; the depletion of these particles in silver as a more mobile :.gold grains are never larger than 0.3 mm. In addition to element in supergene environments. This does not rule high-fineness (898-982) gold, these researchers docu- out the possibility of the galvanic overgrowths of gold merited its new mineralogical mode of occtirrenae of vie- particles with newly formed high-fineness.gold in plac- let purple and purple color, which consisted of a mixture ers. This issue deserves, however, its further studying. of gold hydroxide and fine-grained polytnineralic aggre- In s ite of the fact that newly formed gold- occurs gates of iron hydroxides and iron and bismuth tellurates. P These data and other extensive information provides much less widely han "old" gold in placers, modern technologies make it possible to extract all gold, includ- e evidence that supergene gold can be formed in placers ing its nanometer-sized particles regardless of their and weathering crusts and can migrate with groundwa- . enesis. This approach to the problem discussed in this ters. It was hypothesized [51, 53] that this process can g be reductive and can even regenerate the gold poten- Paper highlights ahe economic 'significance of newly p formed supergene gold. tial of previously worked out placer deposits. For example, Voronin and Goldberg [54] believe that this process can be facilitated by electrochemical GOLD MIGRATION IN SUPERGENESIS ZONES reactions related to aweak electric fieldaround liquid flows filtrating through porous rocks. These researchers Vernadsky [55] evaluated the average gold concen- demonstrated .that the separation of electric charges tration in riverine waters at 3 x 10-10%. Other research- (. durin the flow of solutions brings about a voltage dif- ers [51] assayed this concentration.. in mine waters at g ference and generates volumetric electric fields; which, 1 x 10-~ to 9 x IO-'% (5 i]. Roslyakov et al. [56] .deter- j in turn, induce the concurrent reactions of cathode mined that the Au solubility in waters with Ca sulfate is reduction (precipitation) and anode oxidation. Elec- higher than in waters with Mg sulfate: 4.27 and 2.65 µg/l, trons can thereby be conducted by particles of gold, suI- respectively. The pH of these waters varies from 6.5 to fides, and other minerals. It was established that higher 8.0. The supergene concentration of gold was demon- : ( concentrations of electrically positive metals (such as strated to be controlled by the occurrence of geochem- Au and PGE) in the solutions are favorable for the more ical barriers, such as oxygen,. reducing (hydrogen. suI- active precipitation of these metals on primary mineral fide, sulfate, and carbonate), alkaline, and acid, as well GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 page..-56/127 GNfG DATA RFP(lRT 3 4 8 66' ALEKSANDROV 1 as the evaporation of mineralized waters in acid envi- as dithousuilfate-curate, which is stable-within a broad ronments or in the presence of mineral adsorbents. pH range and can be readily reduced to the elementary. ( Data on the role of heterotrophic microorganisms form. (bacteria) in the dissolution of gold. particles and the The processes of permanent (seasonal) freezing. of later reduction of gold in the form of its newly formed groundwaters in certain areas in Siberia, North Amer- . - masses. are scarce [5?]. Nevertheless, available infor- ica, and. other regions where the gold deposits discussed matiomsuggests that gold can be involved in the biolog- in this paper are situated should notably affect the con- ical cycles of the bacteria, and this.is associated with centrations of dissolved gold. The freezing of water in changes in the surface topography of native gold grains the active soil stratum produces ice that contains prac- with the development of humps and pores whose sizes tically no dissolved salts, which are thus concentrated are commensurable with those of the microorganisms. in the residual liquid contained between ice crystals. The 'gold particles `(0.1-0.2 mm across) used in. the The gold concentrations in this Iiquid can increase by experiments .lost half. of their masses during expert- almost two orders of magnitude. This creates favorable merits that lasted for one year, and the dissolved. gold conditions for gold precipitation. from: these solutions was reduced and occurred in the solutions in the form on the surface of gold particles in placers or at the sur- of very, fine colloid. particles. Their concentrations in face of ice crystals. the sols were 166 mg/1. The authors argue that gold oxi- The occurrence of this process in nature is con- dation and reduction proceeded. concurrently, as fol- firmed by the finds of thin gold films between ice crys- lows, for example, from the development of newly tats at the Yellow Knife deposit in.Canada [60]. The formed crystals, botryoidal aggregates, spongy masses, possible growth of gold dendrites from gold-oversatu- and lumps of newly formed gold on the surface of pri- rated residual solutions during the. seasonal freezing of mary gold particles. The fineness of this gold vanes the thawing stratum in placers in the Kolyma area was from 954 to 746, whereas the primary gold is 843 fine. reported by Kolyasnikov. (61], who believed that the Furthermore, gold migration (and reduction) is morphology of these dendrites inherited the shapes of facilitated by the presence of organic fulvic acids in the dendritic snow crystals and admitted that these den- waters and the. biological activity of microorganisms drites could be overgrown by equant gold crystals and (fungi and others), This phenomenon is reflected in thus thickened to the sizes of normal flat-gold particles. gold precipitation from groundwaters by plants, for Kolyasnikov also believed that the gold potential of example, reindeer lichen and other species, as was depleted placers in the Arctic can be naturally restored repeatedly documented during the biogeochemical by the permanent: regeneration of gold from periodi- studies of gold ore fields, including their magnesian cally freezing groundwaters of the active stratum. skarn types. The role of cryogenesis in the migration and redepo- sition of native gold, including the mechanical trans- ROLE OF CRYOGENESIS IN GOLD MIGRATION Port and concentration of gold particles in soil polygons at the bottom of the active stratum during its seasonal In the context of our research and with regard for the freezing and thawing [62, 63) deserves more detailed location of the deposits described in this publication in study. permafrost and seasonal freezing areas, we attach par- The materials presented above generally character- ncular significance to the cryogenic migration and ize the geochemistry of the evolutionary behavior of regeneration of gold. gold in the endogenic and supergene processes forming Studying the hydrochemical effects of cryogenic magnesian-skarn ore deposits. It was demonstrated that processes on the origin of aqueous solution flows dis- Fe and Cu hydroxisulfides (tochilinite and valleriite) d sem~natmg gold, Plyusnm et al. [58] have demonstrate are a previously unknown important lmk of the genetic. that gold concentrations in waters are usually equal to mineralogy of gold. Our results can be used during the 6.6 x 10-' g/1 and increase to 11.2 x 10-' g/1 in thawed mining operations not only at contact-metasomatic waters and to 15.0 x 10-' g/1 in waters that were. prelim- (skarn) deposits but. also. at precious-metal deposits inarily frozen at a temperature of ~°C: The authors hosted in dolomites, carbonatites, and ultrabasites. The explain these differences by the unusual properties of results of our research confirm the importance of and thawed waters which can dissolve more old, but do g the rieeessit of stud in the rocesses of old re ever- Y Y g P g. g. not consider the possibility of gold regeneration.: ation in supergenesis zones at ore deposits, placers, and Fedoseeva [59] published data on gold migration in the dumps of gold deposits. frozen soils and snow, a process controlled by the phys- icochemical characteristics of icesurface and the prop- CONCLUSIONS erties of intercrystalline liquidlike films.- The presence of .these films was identified within the temperature 1. Magnesan skarn deposits of gold-bearing sulfide range of 0 to -10°C. It was demonstrated that Au and .ores are a promising source of this metal in the form of ( Cu .are contained in the pore solutions in the form of its primary lodes and spatially related alluvial and other ions that can form complex compounds. Gold can occur types of placers. A common feature of these deposits is GEOCHEMISTRY INTERNATIONAL Voi. 45 No. 2 2007 GMC DATA REPORT 3 4 8 Page 57/122 167 URING ENDOGENIC AND SUPERGENE ALTERATIONS OR D GOLD. BEHAVI tial restriction to contacts of dolomites with. REFERENCES " their spa intrustons of predominantly mafic composition or those i 1. D. S. Korzhinskii, "A Sketch of Metasomatic Processes, Studies of Magmatic Ore D i l P M p o ty of syenites, although this does not rule out the necess the ore potential of skarns in contacts with i f n ems rob ain 34 in - 456 {Akad: Nauk SSSR, Moscow, 1955), pp. ng assay o granites and.ultrabasttes and in carbonatites. [in Russian]. 2: S. M. Aleksandrov, V: L. Barsukov, and V. V. Shcherbina, Gold-bearing sulfides .are contained at .these. 2 Geochemistry of Endogenous Boron (Nauka, Moscow, . ...deposits in pyroxene and forsterite skarns and calci- ericlase marbles, dolomites, and magnetite- res h 1968) [in Russian]: 3_ S. M. 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Exploration and Geology (1967-1980)," Dept. Ind: traced in the residual unfreezing liquid of the active Can. Geol. Sect. Bull., No. l (1981}: Aff North stratum during its seasonal freezing and thawing. Thy . . Meinert, "Gold in Skarns of the Whitehorse Cap- L: D 13 gold concentration in the liquid can thereb increase b . . per BeltSouthernYukon," Yukon Geol. 1, 19-43. (1986). almost two orders of magnitude. The :cryogenic con- Gold Metallogeny (NonhAmerica, Australia, 14. S D. Sher centrating of gold-bearing solutions in intercrystalline , . a,~ Oceania) (Nedra, Moscow 1972) (in Russian]. liquid films. in ice can facilitate gold regeneration in 15. M. Ripa, `A Review of the Fe-Oxide Deposits of placers on the surface of gold gxains and particles or at Bergslagen, Sweden and Their Connection to Au Miner- adsorbents. 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GEOCHEMISTRY INTERNATIONAL Vol. 45 No. 2 2007 6MC DATA REPORT 3 `4 8 Page 60/127 ~: A Comprehensive Journal Covering Ati Multidisciplinary Aspects of Theoretics{ and Applied Geochemistry, Cosmochemistry, Organic Chemistry and Chemistry of Environment I A P ~ MAVIK "HAYKA/INTEI~PERIODICA" Pleiades: Publishing N A U X A F Distributed b ~ S' rin er v ~. .P g 6MC DATA REPORT 3 4 $ Fage 6I%127 Contents VoL 45, No~ 2, 2007 Simultaneous English tanguage translatiori of the journal is available from Pleiades Publishing, Ltd. Distributed worldwide by Springer. Geochemistn' !n(ernational ISSN 0016-7029... - Volatiles in Basaltic Magmas of Ocean Islands and Their Mantle Sources_ I. Melt Compositions Deduced from Melt Inclusions and Glasses in theRocks V. 1. Kovaletako, V. B. Naumov, A. V. Girnis, V. A. Dorofeeva, and V. V. Yatmolyuk 105 Petrochemical Systematics of Amphibolites from the Archean Section of the Kola Superdeep Borehole N. E. Kozlov, E. V. Martynov, N. E. Kozlova, T. V. Kaulina, and Yu. P. Smirnov 123 Composition of Rock-Forming Minerals in the Kivakka Layered Massif, Northern Karelia, and Systematic Variations in the Chemistries of Minerals in the Rhythmic Layering Subzone Ya. V. Bychkova, E. V. Koptev-Dvorniko~; N. N. Kononkova, and E. E. Kameneva 131" Gold Behavior during Endogenic and Supergene Alterations of Sulfides in Magnesian Skarns S. M. Aleksandrov 152: Mercury in the Sedimentary Deposits of Lake Baikal V. F. Gelety, G. V. Kalmykov, mtd L Yu. Parkhomenko 170 .Interaction of Cr(III) with the Humus Acids of Soil, Water, and Bottom Sediments. L Ya. Koshcheeva, S. D. Khushvakhtova, V. V. Levinskii, V. N. Danilova, and Yu. V. Kholin 178 Distribution of Metals in Bottom Deposits in the Branches of Selenga River Delta Z L Khazheeva and A. K. Tulokhonov !85 ~ Short Communications "Pseudocyclicity" as a Result of Random Events with Reference to the Rhythmic: Layering of Magmatic Complexes A. A. Yaroshevskii 193 Age of the Magmatic and Metamorphic Processes in the Vodlozero Complex, Baltic Shield: An Ion Microprobe (SHRIMP II) U-Th-Pb.Isotopic Study of Zircons S. A. Sergeev, E. V. Bibikova, D. L Matukov, and S. B. Lobach-Zhuchenko 198 Heat Capacity and Thermodynamic.Functions of Epsomite MgSO4. 7 H2O at 0-303 K V. M. Gurevich, O. L. Kuskov, K S. Gavrichev, and A. V. Tyurin 206 AMC DATA REPORT 3 4 8`.. ,Page 62/-1.27. _ _ I SKARNS AND ORE DEPOSITS OF THE WHITEHORSE COPPER BELT, YUKON TERRITORY, CANADA:. SOME ASPECTS OF PETROGENESIS AND MINERALIZATION AT THE ARCTIC CHIEF, LITTLE CHIEF, AND BLACK CUB SOUTH LOCALITIES (PART. 2 OF 2: DAT~4 SUPPLEMENT) Thomas C. Mowatt (1) June. C. Mowatt (2) October 4, 2007. i (1) Geologist, and Senior Associate, On-Line Exploration Services Inc., Anchorage, .Alaska; c/o Post Office. Box 1.438,- Haines, Alaska 99827 USA- (2) Geologist (Deceased, 1992} GMC DATA REPORT 3 4 8 Page 63/I2Z SKETCH MAPS OF SAMPLE LOCATIONS . (2004-2006),. ARCTIC CHBEF, WHITEHORSE COPPER BELT,. YUKON. TERRITORY, CANADA: Three. sketch maps follow. t.abelled "Page 1 of 3", "Page 2 of 3", "Page 3 of 3". They are not drawn to scale (ie. "cartoons"). Each map depicting, `variously, the locations from which sample materials discussed. in this.. report were obtained. The numbers, and/or letters, representing such locations on these maps: are those referenced elsewhere (above) in the present report, as'well as in the condensed/abstracted field notes, .and the initial analyses resulting from the preliminary examination/"triaging" of specimens, ,which make up the two sections of "supplemental data°, .below, comprising the remainder of this report. GMC DATA REPORT 3 4 8 , Page 64/ly U ., . ~• ~ ~ ~ ~ Y~ V ~ ~ ~ ,~ ~ b ti a~ Q ~ ~ ~ ~. ,~~ ~ ~` '' . -~~ ~~ s ~~. ~ ~ _ _. _ _- `~ ,,~= ~' _~~ ,R, ~a~ A _ ~ y ~. ~ C ` \V a(~ ~ =~- - F. o m ~~~~ ~~ ~~~~~ U~~~ ~ ~ ~ ~ ~ ~~ f ~- ~ GNfCDATAREPORT 3 4 8 wage. 65/iz~ ~~ Y ,~. ~,, ~ `~ - ,~-- ~~ ~ ~~ ~ '~ r ~ ~. ~ >, ~ ~ ~ v ~ ~ i -~.~ a ~, ~. ~ = ~ ~ ~. ~ ~. ~' _ . ~~ - 4 ~_~ ~ ~ ~ ~_~_, ~ ~ -~ ~~ .~ ~~, ~ ~ -~~ t U ,l '7 !~ ~ sp ~ ~ f ~ ~,~ $ l ~~ ~ ~ ~ O ~ ~ ;~ Z ~ c z j ~ `~,.~ ~; ~ ` ~. ~ \ ( ~ '~ L~ ~ ~ ~ ~ ~ ~ ~~ ~ i ~ ~ ! ~ ~ ~: ~~ 1 ` ~ ~., ~ t _~:_ ~' ~ ~ ~ ~~ s t7 2 GMC DAT ~ A REPORT .3 ~ Q Page 67/-127 FIELD NOTES/COMMENTS ON SAMPLES C01_LECTE® AT THE ARCTIC. CHIEF ("AC") LOCALITY (TCM): The sample labeling scheme used is exemplified as follows: TM =sampler's initials, "04" the year,. 2004;. "6" =the sixth month, June; "9" =the ninth day of .that .month; "3" =the tt " sarr2 le locali /site for that da er the field notes, the final number N is that assi ned P tY Y~ p ( ) g to e/this particular specimen.: le., in this instance: [TM-d4-6-8-3-N]. Sample locations are shown on the sketch reaps ("Pages- 1 of 3, 2 of 3, ~ of 3 " }above. - - - FIELD NOTES, 9 JUNE .2004--- ~ June 04- rt - Character samples (carbonate rocks -- [apparently.. "marbles, calciphyres"]--, "skarn" materials, "ores") from rubble-crop/rubble.. Note some "brownish specks" (perhaps brucite, after perclase?) in some of the carbonate rocks? Locality is on the "north rim of the mined-out pit (the "west pit", the larger of the two pits at the Arctic Chief). The. other ("east pit") is lower down the hillside, to the south and east of .the larger pit, and :features "granitic" rocks at the western. end. [TM-04-6-9-1-](Map# S1} 2- No samples thus IabeHed. 3- Just southeast of locality #1. "AC {west)" pit, along "north" rim, just above the entrance to the pit. Samples in-place; or immediately below pit-margin outcrops/exposures,. "tricky" to work on atone. Carbonate rocks "marbles" immediate) ad'acent . to "skarn" materials ( ) Y 1 +/"calciphyre(s)"?, /+/-?. The skarn here appears to .occur as an (originally igneous?) apophysis/projection/finger/lens-like mass into/within the carbonates. Analogous to a "crushed zone" setting? Note some "brownish specks" (perhaps brucite, after perclase?) in some of the carbonate rocks? Presumably the "igneous?"-appearing rocks .here are - or are .related to -those termed in the. literature as "mafic dike[s]"? As observed here: porphyritic (tight .buff-colored phenocrysts of altered plagioclase; +/-), with green-grey fine-grained matrix. These rocks are hard ("ringing"-"bell-banging" when hammered, with sharp-edged fragments), and are in evidence as ~ apparent rubble-crop/rubble(?) here. [TM-04-6-9-3] (Map# 3} Might these so-called dikes .actually represent marginal portions/ofifshoots/border zones/"chills"/rapidly-cooled. variants of the (contaminated/"basification" by assimilation/reaction with intruded rocks/carbonates) [ef. TM-04-6-9-3(?)-2, an apparent. "plagioclase. - pyroxene" rock of interesting "salt-and-pepper" aspect/possibly igneous texture??] "main (gtanodioritic/granitic?)..magma" responsible (thermally and geochemically) for. the bulk of the metamorphism/metasomatism at the AC?? Are these "dike" rocks and/or the/any other "skarn" rocks here at his sample site/locality at least in part "endoskarn", at .least in a certain sense/one sense or another?? Fine grained/porphyritic, rapidly-cooled/quenched variants of a "dioritic"/more mafic magmatic aype (with plagioclase[?] phenocrysts having formed initially during "basification" 1 '- F GMC DATA REPORT 3 4 8 Page 6s/12~ of the main magma, at the periphery. of the main .intrusive body; and "quenching" of the matrix subsequently. during injection into country rocks. as "heal#ied" magma at elevated .temperatures?? With .perhaps some, or perhaps relatively littlelnone metamorphic/metasomatic effects, [even at the relatively high temperatures likely extant, due to the relatively small volume of these melt materials as well as perhaps the physical conditions leading to/permitting their migration/intrusion into the.. country rocks] on adjacent surrounding country rocks into. which this partially crystallized mafic melt was intruded??) ?? [le relatively rapid intrusion, perhaps due to tectonic activity/fractur[ng of country racks, with attendant pressure drop/release, cooling, etc. ??] Perhaps aided and abetted in their .distribution, emplacement, cooling and solidification by structuratltectonic eventslfeatures, in particular fractures/fracture zones, perhaps related to the °contraction phenomenon" associated with the .evolution of the main magma body(ies), as discussedlespoused by Rleksandrov?? [te. perhaps representatives of .the °main magma" extant at depth. subsequent to the metamorphic and metasomatic eventslconditions attendant to the formation of the skarns and related mineralization??j. "Long-lived" {or perhaps only .relatively short-lived) tectonic "crush zones", ie. Featuring/affording porous.: and permeable. zones, reduced pressures; loca[ty andlor for relatively brief periods of time, perhaps .facilitating migratioN "flight"/escape of more basiclless silicic, higher #emperature, lower viseasit5r melt materials as "fugitives", in a sense, from the bulk heat source of the main magma body?? .With or without assistance from tectonic manifestations related to physical differences in main magma body versus surrounding rocks, in addition. to heat differentials/gradients. Is the somewhat casuallsummary treatrr~ent/disrnissat of these. "dikes", especially in terms of their influencelrelevancelsignificance .with regard to the metamorphism-metasomatism- mineralizattvn, as mentioraedlindicatedlsuggested in previous reports, perhaps. mis- guidedlinappropriate/short-sightedlpremature??? A NOT(ONffHRE,4l7 PERHAPS WORTH LOOKING INTO Ft1RTHER. Cf. {below, !acetify #4} photos from opposite ("soothe) rim of pit, featuring views of locality #3. [TM-04-6-9-3) (Map #3) 4- Just across the ~C {west} pit entrance from locality #3, to the south-"ish", Samples and photos looking northward at locality #3, and around the pit to the west. Samples of carbonate rocks ("marbles", and "calctphyres"), "skarn ~ materials,. "ores"; in-ptacelrubbfe-crop. Note some "brownish specks" (perhaps brucite, after perclase?) in some of the carbonate rocks? Note interesting structures to the carbonate rocks and associated .skarn materials {across pit entrance) as shown in these photos. ATM-04-s-9-4~ {Map #4~ 5- Just "east" of locality #3, on northeast side of AC {west) pit. Outcrop and subcrop carbonate rock samples {"marbles", and "catciphyres"}; rubble-crop?!rubble samples of "skarn" materials, "ores", "endoskarn/diorite" material(?). Note some "brownish specks" .(perhaps brucite, after perclase?}: in some of -the carbonate rocks? [TM-04-6-9-5] {!Nap #5) 6- Today also collected grablcharacter samples of rubble from along the road downhill east of the AC (west) pit. Samples likely came from the "AC e t u pit. Samples Taken at 2-F GMC DATA REPORT 3 4 8. Page. ti9/127 -: easternmost end of the smatter. pit area,. along a shoulder on the north side at the opera end of the cut (ie. the end distal from .the- pit "headwall"} into the pit proper. Several photos into pit, with "granitics",+/- (?), at the far- endlkieadwafl of the AC (east) pit. FIELD NOTES, 10 JUNE. 2004--- Photos of Arctic .Chief (east) pit. From about the TM-04-6-9-6 locate. Photos of AC (west) pit. From both the TM-04-B-9-1 and 3 locales,. as well as the TM-04- 6-9-4 locate. 10 June 04- 1-' Below locale 9 June 04-3 [TM-04-6-9-3], rim of AC .(west) pit. Samples of "_skarn" materials, carbonate rocks ("marbles", and "calciphyres°; brownish specks, perhaps brucite after. periclase, noted in many of these), as watt as "dike rocks°(??}. Rubble immediately belowr the semi-intact outcrop/exposure hanging overhead, as welt as jutting out: over the edge of the pit waft (a "dicey" sampling spot --- "n®t a place to spend the night"). Cf. remarks under-entry "9 June. 04-3", above. Cf. numerous photos. [TM-04-6-10-1j(Map #3) 2- A variety of ~character~ samples from rubble near enfrance to AC {west) pit. Most not far from their apparent in-place sources just uphill; others more likely are appreciably out-of- place, from elsewhere inside the pit, moved and deposited here. by activities during the course of developing the pit, etc. [TM-04-6-1.0-2~(Map_ #12) 3- Additional samples .from near 9 June 04-5 la~cality (which cf.). [TM-04-6-10-3](Map #13) Next opted to search for carbonate -rocks of more "original" naturelcharacter, ie. (hopefully) outside the sphere. of influence of the- intrusives, racks: at least of "(ass-than-marble-grade". Drove on up the road beyond the north side of the top of the AC {west) pit; went a couple of miles, with fair but intermittent rock exposures, apparently of igneous/"granitic- dioritic"Imetamorphic? character.. (Perhapsllikely it would be more. fruitful to pursue "unbesmirched/untainted, l,opefulty stratigraphically at least. somewhat "equivalent" carbonate: rocks. along s#rike to the "north- northwest" {or, .perhaps, across the entrance to tale AC (west) pit, into and beyond the carbonate rocks exposed at the rim of :the pit on that 1"south" side; ie. at the 04-6.9-4 locale and along its trend}. Cf. the striking mountainsieie (cf. photo #"36"} expospres some. distance to the north of the AC. Need to check with Mike Burke on this. Although the exposures along the entrance cut of the. "east" pit at AC might .welt have the sorts of "precursorial" carbonate rocks I'm looking for[?].). GMC DATA DEPORT 3 4 8 s- F Page 70/127 4- .Outcrop ("4an sample localtty; "skarn' materials} along .the road at odometer reading.. 184.7, on uphill beyond the top of the AC (west) pit. Other samples here include a piece of float/subcrop/rubblecrop (perhaps. -even road-building/bulldozer-relocated -- if so, from uphill, presumably/most likely??-- and redeposited material?) of "skarn"f~dioritic"? (hornblende-bearing?) rock taken from the "southern" side of the road, displaying appreciable amounts of moybdenite on fracture surfaces.. of broken sample {cf. HAT "new- .type" mineralization??}. The outcrop at this locality crosses. the road, with: evident "skarn" featuring calcite, red-brown garnet, etc. [TM-04-6-10-4](Map# Z/14) 5- Odometer _ 184.7+++, Outcrop; featuring .appreciable .amount of sulphide(s?) - "pyrite?/pyrrhotite??/arsenopyrite"??? on fracture surfaces of broken "diorite" specimen {cf. HAT "new-type" mineralization??}. Outcrop on the. "northern" side of the road. [TM-04-6-~0-5](Map# Z/15) . 6- ,Odometer .reading 184.9. Outcrop at dip in the road, just N/VN of the top of the AC (west} ~ pit. Rocks are "dioritic"?; "endoskarn"??. Darker sample is from outcrop, lighter. one is afloat"/not. actually in place. [TM-04-6-10-5](Map# Z/16) 7- Odometer reading 185.0. Outcrop at the junction with the road aut to the top: edge of the north rim of the AC (west) _pit. Sample of "ska~.rn" (endo?/exo?} materials, with garnet veinlets, etc. [TM~04-6-10-7](Map# Z/17) $- .Same locality as 9 June 04-3 .(which cf.). Photos of pit. Samples -of carbonate rocks, skarn(s}. [TM-04-6-10-8](Map# Z/18) 9- Same locality as 9 June 04-5 (which cf.}. Photos of pit. Samples of carbonate rocks, skarn(s). [TM-04-6-10-9j(Map# Z/19) X- Ended the day's efforts at the Arctic .Chief by taking. a number of "serendipitous° :grab/rubble/character/"doorstop"/"exploration" samples from here and there ("targets of opportunity") along/beside the road :from the north/east(?) edge of the AC (west} pit, which extends "northward" to its junction with the road leading up the hiH. [TM-04-6-90-X1(Map# "Z") '(End field notes, June 2004) FIELD NOTES, 9 August 2004--- Arctic Chief (west) Photos from"NE" rim of pit,. into pit. "Sunrise" shots all around. View. from TM-04-6-9- 1 &3 localities. (Map #s 1 &3}. 9 August 04- 4-F GMC DATA REPORT 3 4 8 Page" 71/127 1-,Samples from TM-04-6-9-3 locale. "Dike" rocks, etc. vs. "hard" ,carbonate rocks. "Contact" between "skarn"1"carbonate" rocks? "Dikes" _ "plagioclase-pyroxene" rocks of SMA? Cf. photos across pit mouth looking toward locale "5": These "dikes" appear .possibly {in photos taken from TM-04-6-9-4 locate) to be' associated with. (?} "tonguesA of "skarn/intrusive rocks" (?} into the carbonates (?). [TM-04-8-9-1 j(Map , #3) 2 - Collected (as rubble/rubble-crop) four large bags of "typical" (?!) garnet-pyroxene +1- skarn "specimensn along .the .road from the north .rim of the pit ---> road leading up the hill. [T6lI-04-8-9-2j (Map # E~~~) Traversed/toured the "southeast<-->southwest" rims/upper benches of the. AC (west).. Many photos from there, and from the pit entrance, as well as from .the: "north-northeast" rim "carbonate" rocks locales. Did same "sketch mapping", via pacing and Brunton c®mpass. (Voted no "granitics" at the "east<--->south" and "south<=-->west" rirr~s of the ~C (west} pit during my approximately "3/4 csf the way ar®und".traverse/tour of the accessible portion of that area. Seems to be all garnet-pyroxene, +i- "skarn" rocks. thereabouts (?j. [[PLAN TO REVISIT]] Collected a number of samples (probablyllikely as rubble-crop) of "typical" (?!) pyroxene- garnet, +l-, "skarn",..from the top)"bench" and edge of the "southwest" (Map# ~), and "southeast" .rims (Map # 21) of the AC (west) pit. Also .collected samples of "ores" -some banded, .from the "easternmost" part. of .the "southeast" rim}- This traverse)"tour° also included the "south" ("headwall") rirn of .the AC (eas) pit area, including photos.. Note "granitics" (porphyritic--very fine grain--fine grain--coarser- grained; ..some contain!ng -- mostly "mafic" -- xenoliths) in rubble above this r!m. [[PLAN:. TO REVISIT]]. (Map# F, & #23[partj). 12 ®ctaber 2U04- Arctic .Chief area. Windy and a bit chilPy this warning up on .the AC. Ice on the windshield, etc., down in the valley at Whitehorse tllis_morning. jTM-04-70-12-1-1 ___>j Collected "ores" (ie. magnetite +l- bornite +l- chaicopyrite +l- ?) from the AC (vast pit entrance, and on inside pit (Map #22B), as well. as uphill (Map #22A) on south side of the pit entrance (in approximately the TM-6-9-4 area). Rubble/float samples.. Some: samples frozen in place: Several "non-ore" specimens of "skarn"-materials, etc.: (from below. the TM-04-6-5-3 area; Map #22} . 5 - F Page 7.2/127 GMC DATA RESORT 3 4 a TM-04-iQ-i2-2.1 --~> Selow, approximately east-northeast, of the TM-04-6-9-4 locale, in the area .peripheral to the "head" of the AC (east) pit. Rubble/float samples of "granitics", "oresn. (Map #23). Left the rather )mpressive molybdenite-laden "foot, specimen" of TM-04-6-i0-4 "B" (Map # Z) with Jim Coyne far his continued edificationlamusement, +J-possible slabbing to look at vein-aiteratian-hest rock characteristics. As R. Zuran put it, examining a piece, "that's a lot of cooly":...:. END OF 2004 FIELD SEASON FIELD NOTES May & June 2005 -1 ~_Ma~ 2005- Arctic Chief (west) Photos from "N E" .comer (Map#s "®", "C'") of rim of pit. Vievrs from, in, at and ground the TM-04-6-9-i , &3, &5 localities. TIVl-05-5-25-~: In-place and "recognizably-displaced" samples- from TM-04-6-9-3 locale. (Map area #C/Map area #3). "Dike" rocks, .etc., vs. "hard" carbonate rocks. "Cantact" between... "dike"/"skarn"(~)/"carbonate" rocks. "Speculatively": These "dikes" appear (cf. photos from TM-04-6-9-4 locate) to perhaps {???) be"tongues" related to/of "skarn/intrusive rocks" (??) into the carbonates.. (?). Or, rather,"merely" dikes from magma intruded either/orfadl (??) prior/daaring/subsequent to the "main magma° event{s?) which were responsible for'. the formation {viz. metamorphism and metasomatism) of the skarns and ore mineralization. [Or, rather, both/ail ®f these (???)l: Samples represent outcrop/"in-place"Irubb(e-crop materials, .either in-place. or not at all far from .being actually in-place. Many of these specimens mere obfiained in-place, at some varying degrees of hazard, from the very "brink" of the (overhanging} .pit rim. Specimens of carbonate rocks {"marbles", and "caiciphyres' ; brownish. specks,. perhaps brucite after periclase, noted in many. of these}; porphyritic as well as more equigranular {"diori#ic"?) igneous (?) rocks {this locality is at the "massive" exposure, not. the "bird"exposure; cf. photos and legends, 2004); "skarn° materials (with s©me magnetite (?), +/-): Some examples of "lenses/zones" featuring garnet, pyroxene, magnetite (?), +/- ad}scent to carbonate host rocks..(Some photos. of latter occurrences). These rocks -occur in a three-part {or more) .sequence, from {from. "left to right"i"southish" to "northish' ; cf: photos): the "igneous"f"dike" rocks, through a , "black" material..interval, and thence irrto whitish/light grey carbonate rocks: 6-F 6MC DATA REPORT. 3 4 8 Page 73/127 ~ - il. As can be discerned on some of the photos taken, the. site of TM-45-5-25-1 shows an interesting relationship between the darkish-light grey-light grey-greenish "dike" (?) rocks exposed in the "massive. exposure" atop tt'~is locality and the .adjoining carbonate rocks. At least in , places, a "zones/"lenses" (?) of very dark green/black materials?) occurs .between these "porphyritic and more-equigranular igneous" rocks ..and the light grey/whitish carbonate rocks.... . There is some/a fair amount of smaller-scale "intermingling" between adjacent "zones" of this .sequence {cf. samples). Some interesting structures/textures are mani#est in same of these specimens. The "black" interval appears megascopically/from a distance to perhaps represent at least in part a "sheared" interval (with apparent stickensides, etc. noted on closer examination, in p(aces). The "blackish" material appears at least in part to be chlorite Speculative "scenarios" for this particular locality might include: 1. "Black" material/zone = a zone of shearlcataclastic materials/gouge, resulting from ructural movement and attendant deformation aloe the dike/carbonate rocks contact z ne st o g subsequent to solidification of the dike rocks (with similar possible scenarios as suggested in #2, below, as to the natureltiming/sequence of metamorphic and/ar metasomatic effects/events (?). 2. "Black" material/zone =contact metamorphic/metasomatic product(s) of dike .magma intrusive into the carbonate rocks (the carbonates either previously unmetamorphosed/metamorphosed-metasomatized/affected by "skarning" ent rocesses riot to intru 'on of dike ma ma ev s / si { } P P 9 O• 3. "Dike" magma coeval with, or an apophysi~ of, -the "main magma" which was responsible for the overall contact metamorphism/rrietasomatism of this deposit locality. Or subsequent to this? Or prior to this? Perhaps, as aguess/impression/"interpretation", the dike magma is (?) an offshoot of the main magma, from the relationships observed at this locale In particular. Some other observations at this locale ("Map #C") seem .worthy of note as wet(: A. Some distance from- this vantage point, in an approximately northuvest "direction, apparent grey-green- rockslmaterials can be observed to occur at and near. the top of the "steeply- dipping" sheer-#aced "North" wall of the pit. These. grey-green rocks/materials might well be "on trend" -with. the. "massive' exposures (te. at locale "Map #C") and/or "the bird" dike rock (also grey-green in aspect) exposures (at the "NE" Rit .corner .rim. area, on the "N" .side of the pit entrance, respectively [cf. 2004 photo ~, as well as photos taken. this. date]}. Or, these grey-green rocks near and at the top. of the "N" pit: wail might {?), alternatively, be a continuation (across the pit, ie.) of a possible (?} dike/intrusion exposed. in .the the "S- SE" -.wall of the pit, adjacent to the carbonate rocks +/- of locale Map #4. {This possible.. [?j dike/intrusion in the "S-SE" wall of the pit is the "V-shaped" feature, with reddish margins, shown in photographs [2004, 2005] from the "N-NE" rtm of the pit, looking approximately South.) B. Also note photos of the above-described "V-shaped" feature in the "S-SE" welt, as-taken from the "NE" corner area on 25 May. 2005. Note especially those featuring the carbonate rocks of Map #5, .with the "on-trend"/equivalent (?) carbonate rocks of Map #4 in -the - - distance across the pit entrance, with the "V-shaped" feature to the west of the carbonates, in the "S-SE" waif of the pit. " C. Need to revisitfcheck/sam le the rim above this . V-she ed feature, as well as the it p p p below. it. Unfortunately the .steep/essentially vertical pit wallitse~f, further threatened/endangered by its overhanging. rim, is not readily accessible/sampled in-place: '' 7-1= .G M CD ATA REPORT 3 4 8 Pa e 74 127 ~ ~ Also .took other photos from site "Map #C" (and of the site. itself as well). TM-05-5-28-2: Samples (two) from outcroplin-place- of the "steeply-dipping" sheer-faced. "northeast" pit wall near Map# "0" locale. "Pyritic siltstone" unit (?), or ??. Also several photos from this site. TM-05-5-25-3: Also collected a number of garnet-pyroxene +/- .samples from the road from the .north .rim of the pit <---> road up the hill (the -areas of Map#s "®" <--~ "Z"). "float-rubble" materials/"character samples". "Exploration samples": One never knows what might be lurking inside these (or any) types of rocks. As l learned way back when....>.. Other:. photographs. taken from Map # 5, #1, etc., from this general area. of the "NE" corner of the pit rim... 26 June 2005- ARCTIC CHIEF (west)--- - 1 Character samples: ("-A") from "Map - #3" locale- ::magnetite +!-. Character samples ("-B") from the northwest side of the pit entrance: magnetite, +/-. [TM-05-6-26-1-A, B] NOTES: View of AC (east) pit,.from AC (west) pit entrance :.Sketch in notebook. Accompanied by D. Hogarth. END OF 2005 FIELD SEASON. FIELD NOTES. August 2006 -1 22 August 2006- Arctic Chief. (west), Whitehorse .Copper Belt, Yukon Territory, Canada Refer to enclosed sketch maps, above, for locations. of the- samples described in the.. following notes of this date. TM-06-8-22-1: Atop the veneer of carbonate rock rubblel"rubble-crop" which .overlies the "massive" .exposure of a/the dike at this site (Cf. Map#f: ). Portions of this: exposure of dike rocks were sampled: Samples of the carbonate rocks were also taken. All samples were of "loose" material.. However, the .dike rack samples, in particular, are "sub-crop" of adjacent in-place portions of the dike. Samples feature "banded" and "dioritic" (?) rocks, among other types. [Refer to work of previous years at this locale for additional comments, details, etc. GMC DATA REPORT 3 4 8 a - ~ Page 15/127 TM-06-8-22-2: Locality shown on above map ("Page 3 of 3") is in the AC pit, up on the side of the wall of the northern corner of the pit entrance, where it adjoins/meets the wall of the main portion of the. pit. ...The geologic relationships displayed at this locality are shown, variously, in the numerous photographs taken of this site in previous years (see "photo index" files). A rough sketch, ("Attachment TM-06-8-22-2-"), cf. billow, made. in the field shows the general spatial relationships of the materials comprising the "tongue" of darker materials into the host carbonate rocks.. This sketch/"geo-cartoon" is not to scale, .since direct measurements: were not readily feasible due to difficulty of access. Approximate dimensions were estimated in the field, as .well as by comparisons, .from photographs, to the dimension of the exposure of sill-rock above this ocation which .was pace-measured previously: This is a very. interesting,. perhaps "key", locality. It is the location of acopper-bearing "tongue" of dark .materials ("skarn", +/-, presumably[?]) projecting into carbonate rocks at/near/along the apparent crest of a structural fold in the host .carbonate rock sequence. This is the "gaudy" feature shown in many. photographs, taken from. various sites, during field work of previous years (2004-2005). Samples were taken. of all principal lithologies/zones/etc: ~ Represented were "hast/country" carbonate rocks. (the predominant carbonate rocks in the sequence exposed here are light grey, with subordinate proportions of discrete .interbedded sedimentary (presumably [?j) horizons of darker grey carbonate rocks [cf. photographsj). Also sampled were a variety of darker rocks, representative of "skarn-like" and "igneous(?)" materials. Samples included in-place materials, as well as_some "sub-crop" and "rubble-crop/float'; the latter .samples were obtained immediately below those portions ofthis location not readily accessible. (Essentially vertical, or overhanging, wails in places.) SUPPLEMENTAL NOTES REGARDING SAMPLE LOCATION "TM-06-8-22-2-A-, B ; C ": (Cf. "Attachment TM-06-8-22-2-") TM-06-8-22-2-A-: Specimen "-1 ": from the .central/medial portion of the medial. zone ("X") of the greyish.- greenish rocks:. Specimen "-2": from zone "X", intermediate between specimen "-1" :and specimen "-3". Specimen : "-3": from -zone °X' ; adjacent to the upper part of zone "Y". Specimen "-4": from .zone "Y'; nearfadjacent to the lower part. of zone "X". Specimen "-5": from zone "Y" C---> zone. "Z" .border area: Specimen "-6": from zone "Y" <---> zone "Z" border .area; mare distal. from zone "X" than specimen "-5". TM-06-8-22-2-B-: .Specimen "-1 ": from zone "X". Specimen "-2":.from zone "X" C---> zone "Y" "contact". Specimen ",3": from.. zone "Y" <---> .zone "Z" "contact". Specimen "-4": from zone "z„: Specimen "-5': from zone "Z", .somewhat more distal from zone "Y" than specimen "-4". Note Cu-staining/mineralization in/on this specimen, taken at the edge of the prominent GMC DATA REPORT 3 4' 8 s - F Page 76/127 r, ~ ~ ' ~ ~~ ~ ~~ a -t ~ ~ ~ ~. u~ ^~." , ~ v ._ ~ _m 4 ~ ~~ ~ W ~~ ~ ~~ °~ ~ ~ ~ ~a a~ ~ ~ ~~ o ~~ ~ _ `~ ~ ~~ ,. f C zo ~ ~.,. a a / ,.; ~ o ,... ~, .,,.. ~ ~ ~ ~~ ~ ~ ~ ~ ~ ~ ~~ w ~ _~~~~ ~ ~ ~~ ~ ~ 3 V 3 ~ t V ~ '~ ` ~ ~ ~~~ ~~ . ~ ~. d ~ .,~ -~ .~ ~. w Q ~ ~ ~ ~ i ~ ~ v 6MC DATA REPORT 3 4 8 Page:. 77/127 green area shown on photograph #5 (and other photographs which show this "tongue- liken geological feature). Specimen "-6":.from. -zone "Z", more distal from zone "Y" than specimens "-4" and "- 5". TM-06-8-22=2-C-: - Specimen. "1 =,: from zone "X,, ~---> zone "Yn. Specimen "2": from zone "Z". The two specimens from TM-06-8-22-2-C represent materials. from. the (easternmost) "tip" of the "tongue-liken feature, at the "end" of this .structure .where it terminates (in this exposure) against countrylhost/wall rocks. The six specimens from TM-06-8-22-2-B represent a "cross-section" of this.#eature, further to the west from the "-2-C-" location. This .section was taken from the medial "core" to the lower. edge of this "tongue", :into the wall rocks. The six specimens from TM-06-8-22-2-A represent artother "cross-section", further. to the west from the "2-8-" location, toward the western end of the exposure of this tongue-like feature. This cross-section also was taken from the media! "core" to the lower edge of this "tongue", .into the wall rocks... The attached sketch (("Attachment T M - 0 6 - 8 - 2 2 - 2 -"} roughly depicts the relationships of the samples taken to the "tongue"-like" body overall.. Some comments on the character of the `zones" as adapted .for purposes ofi field sampling are as follows: Zone "X": Made up of grey-greenish rocks of apparent (?) igneous. aspect. Grain size of the specimens shows a general decrease from the central/medial portion of the zone outward towards zone "Y" (specimens "-2-A-1" ---> "-2-A-2" ---> "-2-A-3"). Specimen- " 2-A-3" is adjacent to zone "Y", and features porphyritic texture, with-an aphanitic groundmass, perhaps suggestive of a "chill zone" of sorts. Specimen TM-06-8-22-2-C-1 is somewhat more complex in character, having formed out at the "tip" of the "tongue". Zone "Y": Comprised of reddish-brown/black rocks of apparent °skarn" aspect, featuring. apparent garnet,- pyroxene, magnetite, +/- copper minerals, +/-?. Zone "Z": Consists of wall/host/country rocks of carbonate .composition, variously affected by metamorphism/metasomatism +/- "veining" (magnetite?I+/-??). Zones "Y' "and "Z' ", which. were not sampled due to appreciably greater difficulty of access, appear to be essentially similar ("mirror-imaged", so to speak), in general, to zones "Y" and' "Z°, respectively, "peripheral" to zone "X". Further musings on the TM-06-8-22-2- location are as follows: This geologic feature apparently represents a "tongue" of skarn and skarn-related materials, .projecting into .adjacent carbonate rocks. This location is apparently marginal`to the. previously. present principal mineralization!"ore-body": of magnetite-bornite- chafcopyrite, +/- ,now "mined-out" from the AC (west). pit. i 0 - i= GMC DATA REPORT 3 4 8 _ Page zs/127 Perhaps it is not .atypical,: thus, of the conditions/situation.. extant during/responsibte fior the more extensive mineralization of the .main ore zones. Eiopefully providing an example, though at a smatter scale/"in miniature", perhaps, of the .processes and resultslproducts at #hts deposit. Possibly a vestige of more substantial skarn formation related to` a portion of the. ore body. This feature/location is on the margin/peripheral to the mined-out .pit. And there is magnetite,- copper staining, +/-? ` at this site.. Copper staining reflect bornite, andlor chalcopyrite, and/or......... ?? , .Apparent(?) presence of certain silicate minerals (viz. forsterite?, serpentine?, phlogopite??) indicative of a magnesian .skarn situation? The carbonate countcy/wall rocks are "on trend" with the periclase {brucite} marbles just to the north. of this site. The .nature of the :zone "X° apparently ignE:ous (?) rocks {ie. "dioritic", "porphyritic andesitic I?]"j is of interest, as are the grain- size/textural relationships/"intrusive" characteristics noted. Are theseigneous" rocks. representative(?)Jindicative of the characterlcomposition of thee."main magma' responsible for the the metamorphism/metasomatism at the. AC (west), +/- elsewhere in the area? And/or "modified" by assimilation/contamination/reaction etc.: etc. (?). Cf. other samples taken on August 8, 2046 .elsewhere in the AC (west). pit, especially those of "dioritic" (??) aspect collected in .the vicinity of the sumplpond/"g~ory- ho~e" near the southwest corner of the pit floor (?): What is the relationship of these rocks with those of the "dikes" in the: neighborhood? The porphyritic specimen collected from the "tongue" has a fair .degree of similarity. in (megascopic) aspect to some of those, dike rocks.. Though presumabiylsupposedly these dikes were "later" than .the metamorphism, metasomatism, ore deposition.. The apparent lack of significant "contact" metamorphic effects between dike rocks (for example at the "bird-like" dike .exposure [cf. TM-06-8-22-2-5-], or its (likely] extension at .the. nearby "massive silt" exposure) and immediately adjacent carbonate watt rocks is suggestive/informative. As .are the observed relationships in this "tongue". TM-06-8-22-3: See above map ("Page 3 of 3") for location. -Samples of "rubble-crop/ffoatn materials collected along a traverse from the south wall of the pit entrance, where it meets-the main wail of the pit, to the south corner of the pit. The, traverse proceeding along the foot/tower flanks of the southeast wall of the- pit, just below the near-vertical/verticatloverhanging watt. "Character" samples were taken, from the pit entrance {carbonates), thence southwestward. Collecting, sequentially, dark "orels", +/-, followed- by "skarn°-materials (pyroxene/garnet, +7-) to the southern corner c+f the pit Some white. materials (carbonate?l??) were collected beneath exposures observed higher above in the pit wail Photographs of the AC (west} pit. show general relationships/features.. Faults/fault zones, some with .associated alteration (vts. green/greenish-yellow, rustyfreddish-brown, esp.}, were noted with moderate frequency in the pit wall along the course of this traverse. One such zone occurs at the south corner of the pitwhere'the southeast and southwest wails of the pit meet. TM-o6-8-22-a: See above map ("Page 3 of 3"} for location. Numerous photographs (over the years) #eature some views of this location. Traverse was along the: footlla~vermost flanks. of the southwest pit wall, at/near the base of the vertica~lnear-verticatloverhanging watt. Samples of rubble-crop/float character. Rocks predominantly "skarn"-materials (minor exceptions being. several "white patches" to 'this southwest wait, reminiscent of similar # 1 -fi= Page .79/127 GMC DATA REPORT 3 4 8 teatures observed in the southeast wall of the pit)... This "skarn" comprised principally: of pyroxene and/or garnet, with associated "pockets" of eu/subhedral calcite, garnet, -minor chalcopyrite, +/-....). No "granitic/gr•anitoid" .rocks were noted along this wall.. of the .pit. However; distal from .the wall proper, toward the center of the. pit, .there is a relatively smolt depression at the-.deepest part of the floor. A "sump"/"glory-hole", of sorts; presumably. As noted over the three years of this study,, subject to flooding, and formation of a small "pond". Though this "pond" was .appreciably - "smaller/drier" on ;the present date. At this location, a pile {"float?!rubble?/subc~op"?) of dark {"dioritic"?) rocks was noted (and sampled)... Perhaps representative. of rocks, occurring. in/near/below .this. location? Indicative of similar/"dioritic" {?) rocks in place below? Perhaps representing "exoskarn" (??), or/and "endoskarn" (??). A portion. of a .phase/carapace/she!!/border zone. of the "main magmatic mass" related to/responsible for the AC metamorphism, metasomatism, skarn and ore formation?? TM-06-8-22-5: See above map ("Page 3 of 3") for location. Numerous photographs feature some. views of ` this docation. Locality is toward .the top of the north wall of the. AC (west) .pit .entrance. At the contact between the "bird-shaped" exposure of the dike and the adjacent/transected carbonate rocks. Samples were obtained .from the. area of, and near, the "chinlthroat" part of the "bird". Cf. TCM photographs from previous years (2004, 2005) and this. date. In-place/outcrop .samples of carbonate rocks and adjacent dike rock. Also some samples as "float" from .this area: Also other samples of rocks as "float/rubbte" in the immediate area. Na specimens containing both carbonate rock and adjoining dike rock together in one sample were obtained, as all attempts to obtain such. a sample succumbed to the blows of a hammer, aril the two lithologies "parted company". The bond between these carbonate host rocks and the intruded dike materials is not physically strong; apparently a "sharp".contact indeed, here: Only relatively minor alteration tuts: some slightlmoderate shearing/gouge, "serpentinization"//+/- (?), of the igneous .rocks was noted. The white-buff-very light grey carbonate rocks give oft a "ringing/tinkling/be11-banging" sound under the hammer or when pieces are struck against one another. Specks of tight-brownish brucite-after-periclase apparent in these marbles. The igneous .rocks are dark .greenish-grey, aphanitic/very fine- grained at the immediate dikelhost rock contact, with larger grain size (in places porphyritic, with apparent plagioclase, +/-?, phenocrysts) developing .with distance, from the .contact. It appears. (from the nature of this contact, and/or the tack of skarn or ore formation [?j) unlikely (?) that appreciable (additional) contact metamorphic (+/- metasomatic) effects occurred in the host carbonates, due to thermal or'other effects related to these adjacent igneous "dike" rocks. The carbonate rocks presurnably having. been. previously. subjected. to the periclase marble level of `metamorphism, in more pervasive/areaf fashion, preceding the formation of this dike here j?]. White these °dike" rocks themselves lack obvious features attributable to such a level of metamorphism, hence appear to have been emplaced. "post" periclase marble formation. END OF 2006 FIELD SEASON 12-F page 80/127 GMC DATA REPORT _3: 4 8 ` COMMENTS'ON PRELIMINARY ANALYSIS!"T'RIAGING' OF ARCTIC CHIEF SAMPLES (TCM): All field samples were subsequently examined. further, in preliminary fashion ("triaged°); by TCM in Haines, utilizing hammer, chisel, hand lens, acid bottle,. and a 30x/60x stereo microscope on rock surfaces (freshly-broken and- otherwise). In some select `cases, .also examining grains-in-oil materials using apersonally-owned petrographic microscope. Deferring to S. M. Aleksandrov ("SMA") fore decisions as to thin-/polished-section .petrographic analysis, etc., as he might see fit. In any case,-the "low-budget°. circumstances precluding. appreciable petrographic thin-/polished-section. preparation. and analysis by TCM. A substantial amount of detailed analyticalllaboratory notes accumulated as the result of this preliminary examination/"triage" stage.. Including observations, commentary, sketches, and photographs. The stereo microscope can be a valuable tool indeed: Due to the accumulation represented, they are not included en toto -nor Even in any great detail- in the present report. TCM can be contacted regarding specific interests, questions, etc. Selected materials (about one :hundred specimens, in all) were then mailed to Dr: Aleksandrov, at the V. I. Vernadsky institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, for examination, evaluation, and further analysis as he deemed appropriate to .his own ongoing research.. This latter. work included .hand specimen, petrographic microscope; microprobe analysis, etc. of representative materials of particular interest. .The following are some selected .comments, as culled from the analytical notes (TCM) mentioned above. Of particular interest were observations dealing with samples which -- the entire specimen; or portions thereof -- were subsequently. sent to SMA. Especially the periclase (bructte) marbles; calciphyres, banded rocks. and "ores", etc. bescriptions, and sketch .maps, of field/sampling localities are. presented elsewhere (above) in the "Data Supplement" section of the present report. The sample .labeling scheme used is exemplified as follows: TM =the sampler's initials; "04" =the year, 2004; "6p =the. sixth month, June; "9" _ the ninth day of that month; "3" _ .the sample locality/site for that day, per my field notes; the final number ("N") is that assigned to a/this particular specimen. le., In this instance [TM-04-6-9-3-Nj. 1981 Samples- TM-81-7-3-0-7: "Skarn°. Garnet, pyroxene major minerals. Subordinate. to minor amounts of "calcite/ carbonate"(?), magnetite, quartz, epidote, actinolite (w/chlorite?), idocrase, chalcopyrite, serpentine(?). And/or .perhaps same bornite (?), tremolite(?), wollastonite(?). Garnet: Eu/subhedral, to anhedral, massive; reddish-brown; often enclosed/surrounded by , pyroxene, calcite. Pyroxene: Euhedral-subhedral,. to anhedral, massive; dark green-blackish. Calcite: Euhedral-subhedral, to anhedral, granular; patchy .:massive; pink-salmon-orange- white-clear colorless. Quartz: Anhedral to (some) subhedral; colorless, clear, glassy. Magnetite: Octahedral and cubic. euhedral crystals; black. Some apparent magnetite. might actually be bornite(?): 1-A GMC DATA REPORT 3 4 8 Page i31/127 Epidote: Euhedral, and also less-well-developed; lemon-lime to pistachio cafor. "Actino(ite/chlorite/tremolite"; "serpentine", in- part{?): Sheaf-like crystals, eu- subhedral, and anhedral granular/massive; pate/light green to green. Ser{~entine: Fibrous; light greenish-whitish-colorless. chalcopyrite: Eu-subhedral, and as less-well-developed crystals. Assemblages/relationships:. _ Magnetite occurs within quartz, epidote, calcite, and adjacent to chalcopyrite. Epidote occurs on/after black pyroxene; some of which is eu-subhedral Garnet occurs within calcite, as well as intergrown with pyroxene. Serpentine occurs with.. "tremolite/actinolite". Quartz encloses magnetite, epidote; is noted "adjacent to" chalcopyrite. Quartz-epidote-garnet-.calcite-pyroxene-magnetite. 1Nhite granular wollastonite (??) adjacent to/on calcite;. in veinslfracture fillings, adjacent to garnet. Some (at least) of the apparent "wollastonite" might actually be ("weathered" ?) calcite (??, +!-?). "Vug-like" patches. (maximum dimension observed abou#10 cm.) of "calcite%arbonate" .(euhedral and less-well developed), garnet (euhedral and less-well developed}, pyroxene (euhedral and less-well developed), quartz (anhedral), chalcopyrite. Grains range from +/- 2mm to substantially larger, .and are well-developed crystals; for the most part. These "patches/vugs" are disseminated/scattered throughout the specimen, the remainder of which consists principally of pyroxene and garnet, coarser-grained/more massively-developed.. This latter type of intergrown garnet and pyroxene; +/- minor. amounts of "alteration products" and scattered "dark/black opaques" comprise the bulk of this "skarn material/rock". These "vugs/patches" are suggestive, in terms of general petrologic aspect,. as well as geochemical, mineralogic, and textural. characteristics, of some form of "late-stage/last gasp" crystallization related to relatively "volatiles-rich" fluid(s). There is a °pegmatoid" aspect to .them. Theis made of occurrence, as often vaguely-defined features within avaried-size mosaic principally composed of "massive" garnet and pyroxene, is striking. Typically, `somewhat "vaguely-defined", yet generally readily. discernible boundaries/borders..between "patches/vugs" and surroundings are observed. The carbonate seems akey -the "typical" -feature, the essentially omnipresent mineral of these "patches". Together. with-.the quartz; and sulphides, +/- "epidote, .serpentine, .etc., suggesting concentration of CO2, Si, some forms} of S, and,. likely, H2O, +/-, presumably in a °fluid" phase(es?), within a surrounding environment of Ca-Fe-Mg-rich materials. TM-81-7-30-2: "Skarn°. Garnet; pyroxene major. minerals. Subordinate amount of "calcite/carbonate"; minor/trace amounts of magnetite, quartz, epidote, actinolite,. serpentine{?) chalcopyrite; malachite, bornite. "Possible" (?) pyrite/pyrrhotite/arsenoprite; _ and/or (??) some tremolite, wollastonite, talc. Traces of several fractures noted, with calcite andlor quartz on fracture surfaces, Garnet: Eu/subhedral, to anhedral, massive; reddish-brown; often enclosed/surrounded by pyroxene, calcite... pyroxene:, Euhedral-subhedral, to anhedral, missive; black to dark .green-blackish. Intergrown .with, often enclosed by, garnet. Calcite: Euhedral-subhedral, to anhedral, granular, patchy massive; ,pink-salmon-orange- white-clear colorless. 2-A - GMC DATA REPORT 3 4 8 Page s2/12~ Quartz: Anhedral to (some) subhedral; .colorless, clear,. glassy. Magnetite: Octahedral and-cubic euhedral crystals, and as less-welt-developed grains; black. Same apparent magnetfte might actually be bornite(?); or other mineral(s). As well, some of the magnetite might represent -perhaps pseudomorphically -replacements of pre-existing minerals (viz. esp. "boraces"?) Epidote: Euhedral, and also less-weU-developed; lemon-dime to pistachio color. "Actinolitelchlorite/tremolite"; "serpentine", in part(?): Sheaf-like crystals, eu- subhedral, and anhedral granular/massive; pale/light green to green. ..Serpentine: Fibrous; light greenish-whitish-colorless. Chaicopyrite: Eu-subhedral, and as less-well-developed crystals. - Bornite: subhedral and less-wet{-developed grains; black-purplish/bluish. Assemblages/relationships: Garnet after pYroxene. Massive pyroxene -with the appearance of "being engulfed/altered by/to" garnet. Calcite after pyroxene, garnet. Minor/traces of epidote,..+/-, on pyroxene. This specimen also features "vug-like patches" similar to those described above (cf. TM-£1- ?-30-1 ). 2004 Samples- TM-04-6-9-3-t: Calciphyre. Calcite, with marble texture. Disseminated brownish. spinet(?), as well as apparent brucite pseudomorphous after periclase. (Cf. remarks on similar appearing periclase [brucitej .marble under TM-04-6-9-3-9, :below). Other minerals noted are forsterite; phlogopite/I+! serpentine?, talc? (after/adjacent to forsterite), talc(?); magnetite (?), or perhaps other black mineral(s). Magnetite might (?) be pseudomorphous after Mg-Fe borates(?), +l-: TM-04-6-9-3-2: A "granitic"-aspect rock. Featuring fractures filled with epidote, calcite, quartz(?}, magnetite(?). Rock also features black eu-subhedral pyroxene(?)/amphibole(???) [shows- .. some .apparent "approx. 90-degrees° cleavage]; plagioclase (note [subhedral] crystal morphology, cleavages); quartz{?); some .magnetite(?) +/- ..associated pyrite(?)/chalcopyrite(??}, all altering to "limonite". Also some epidote, on ..fractures, and in "vugs(?)" (after ..calcite?, etc.?), as well as marginal to - as alteration of(?) - plagioclase. A "quartz dioritic" -- perhaps a "quartz gabbro"(?) -- rock (now). "Altered" rock(?}/"endoskarn"(?). Or representative of a °plagioclase-pyroxene zone", per SMA. TM-04-6-9:-3-3: Zoned magnesian-skarn material. An excellent example of its type.., Five distinct zones/portions occur in this specimen (the specimen is approximately 13 cm in maximum dimension). A zone (on the order of 3 cm, as exposed) of periclase (brucite}.marble occurs at one edge of the `specimen: (Cf. remarks on similar-appearing periclase [brucitej marble under TM- 04-6-9-3-9, below). 3-A GMC DATA REPORT 3 4 8 ` Fage s3/127 Next to this fs a zone. approximately 3-5 mm in .width, comprised principally of reddish- brownish .garnet (?), with associated quartz?, chlorite??. Next to this is a zone (on the order of 2 cm wide) consisting principally of dark greenish/black pYroxene. Followed in turn by a zone, about 4 cm wiide, made up principally of phtogopite, +/-. Next to this is a zone of calciphyre, occupying the remaining approximately 2 cm of -the specimen, .along this "traverse" across its surfaca parallel to the maximum dimension of the .:.specimen. Perhaps representing a "vein-like" development` of skarn? -With similarities to sample "- 1 ", above. Portions of the specimen consisting of marble are principally calcite, with disseminated brownish. materials?), some/most of which appears to be brucite after periclase, while some perhaps is more likely spinet(?). The "calciphyre" lithotogy features. major. calcite, subordinate forsterite(?)/related alteration products (viz. "serpentine?/ phtogopite?, +/-?), as well as -- perhaps -- trace amounts of magnetite (?) and/or spines (?), +/-? (Compare this specimen with specimens TM-04-6-9-3-10; -1 t; -12). TM-04-6-9-8-4: periclase (brucite} marble; calcitic, white-fight grey: Containing sets of darker- coloured/greyish cross-fractures. The fractures "filled/healed" with clean: -- hence the "darker, greyish" effect -- carbonatefcaicite(?}. fe. "self-healed/recrystattizedA. "Crush .zones(??)". Rock otherwise rather homogeneous, mineralogicatly and texturally. Though small disseminated brownish .specks occur, somE: such being brucite after periclase(?), as .well as (some) spinal(?) and/or......... ?? (Cf. remarks on similar appearing periclase [brucite] .marble under TM-Q4-6-9-3-9, below): Specimen is a hard,"belt-banging" rock, which rings/clangsltinkles nicely under hammer blows; or, especially, when thin slivers of the rock are struck together. "Chattering rocks": which. chatter.. on -- amiably...... or irritably......, according to one's mood of the moment -- ; as .one makes. his way -- or, more frequently, stumbles along, slipping and: sliding, ---over accumulations of rubble/float fragments of this lithology. The sort of rocks perhaps one might. be able to .map "by ear", or even in .the dark (?). Sharp edges, pointy corners, too'........ TM-04-6-9-3-5: Carbonate rocks. periclase (brucite) marbles. Two. °varieties" (sedimentary layering, apparently[?)) manifest in this specimen; one essentially white, the .other "greyer"("carbonaceous/graphttic"?), Wfth rather. abrupt/sharp contacts between these "varieties°. Set(s) of intersecting fractures transact bath of these varieties of rocks, cutting across both similarly without interruption.. These fractures are similar to those mentioned in sample TM-04-6-9-4 (above), perhaps/likely,. as "self••healed"/recrystallized crush/shear zones. Minerals present feature a "glassy" clear "quartzy"-looking crystalline material, intergrovun with a duller, white, crystalline material which.. shows subhedrat crystals (as "stubbyish forms/taths° }when in lesser proportion to surrounding "quartzy" material The e latter. also exhibits some eu-subhedral .aspects here and there,. possibly of "quartz aspect" (?). The "lighter" portion of the specimen consists of predominant "white" carbonate (calcite} material; the "greyer".portion of the specimen, as well as the transacting fractures/zones, contain carbonate/calcite, as .well appreciable "quartzy-looking" mineral. A "siliceous"/"quartzose"(?} periclase (brucite) marble. (Gf. remarks on periclase [brucite marble under TM-04-6-9-3-9, 6eiow). 4-A GMC DATA REPORT ~~ 4 8 Page s4/127 Trace/minor amounts of fine-/very-fine-grained: black crystalline material{s?) occur here and there, including .within fracture zones. These .perhaps consist of graphite(?)!magnetite(?)/+/- ??. Also disseminated in this specimen are many somewhat obscure. "brownish .specks", which perhaps/likely (somewhat "unclear° in this particular specimen) are brucite, after periclase: TM-04-6-9-3-6: Carbonate. rock(s). periclase (brucite) marble. y Two variants in this specimen. One a dark grey, the other a lighter grey-white, apparently interbedded {?}. Some fractures, .especially apparent/only present{?) in the darker variety of rock ..here, .with tighter materia! (carbonate/calcite, +/-?} along the fracture surfaces. Might{??) the lighter "beds"/"layers" of carbonate rock actually be °wider"~"mega" shear zones, with recrystallized carbonate, +/-?, along/within these zones {??). One edge of one of the wthite "zones°/"layers" exhibits a .distinct "ringing"/"belt-banging" character when. struck sharply.. -The darker grey material features greyish vitreous-looking mineral(s); carbonate/quartz(?)/+/-?), and {appreciable) associated dark/black disseminated materials?}. The latter possibly- graphite?/magnetite?/?"borates"?/or ??. Note, in this darker material, brownish subequant {on weathered surface). grains of apparent brucite after .periclase. And/or spine/(??). !n the .lighter material, there appear to be at least two "predominant'. minerals: one "dul4 whitish", the other. a light grey, and perhaps "more vitreous"-looking. Likely periclase/ brucite, and calcite. (Cf. specimens TM-04-6-9-3, 4, 5). (Cf. remarks on similar appearing periclase- [brucite] marble under TM-04-6-9-3-s, below). In the darker material in this specimen, these two "predominant" minerals also occur, but with a more substantial amount of black materiais(s?); viz.graphite? (magnetite?/ "boraces"?/+/-??. These. "whitish" versus "light-greyish" minerals are present in approximately coequal proportions in both the lighter and darker .portions; ie., the "lighter" and the "darker" carbonate(?} rocks/layers comprising this specimen. Hence likely (?) represent periclase/brucite and calcite. ((Might at least some of the "grey° material be fluorite(???); note an optical impression of sort of a "greasy" appearance, here and there. Though perhaps more likely this is also peric{ase/brucite.)) TM-04-6-9-3-7: White carbonate rock. periclase {brucite). marble. With at least ,two sets of intersecting fractures. The earlier set features greyish ("quartzy- looking") material (cf. specimens TM-04-6-9-3, -4, -5, -6, per above). The dater set features sortie similar material, though containing appreciably more black material/mineral(s) - (graphite?/magnetite?;+Mg-Fe borates??/tourmaline???/+!-?). The white- carbonate material appears to consi>t of approximately coequal amounts of a white, "dullish-appearing" mineral, and. a mare "vitreous-appearing", clearer ("quartzy- looking") mineral (which latter, however, is noi: as greyish- as the "quartzy-tooking" mineral in/associated with the fractures. (Cf. remarks on similar appearing .periclase [brucite] marble under TM-04-6-9-3-9, . below}. In the "later" .fracture-fillings/"veins", .the black mineral{s) are the principal constituent, writh apparent "spreading"/"diffusion" laterally fito the country rock 5-A Page 85/127 GMG DATA REPORT . 3 4- 8 -- .surrounding these "veins". Much of the "vein-filling" is also adarkish-grey. "quartzy- looking"/[rather, carbonate(?)~ material (cf. the pfiases noted in samples TM-04-6-9-3, - 4, -5, -6, as above}. This specimen presents the aspect of "vein-filling" material, perhaps along "crushed" and "recrystallized" zones/fractures. Featuring a' "self-healing".:..situation, in this particular case in concert with deposition of the black. mineral(s)/material(s}. The dark veins offset the lighter .grey veins, slightly but ;noticeably. These darker veins are' somewhat remindful of similar features. observed at :the magnesian skarn-related localities of Lost River/Brooks Mountain/+/-Tin Creek, western Seward Peninsula, Alaska. Some buff/tan/"rusty° weathering (presumably) effects noted an older!"pre hammering° surfaces of this specimen. Also noted on these surfaces are a number of .apparently. "residual" periclase --> brucite "hates"/depressions, displaying euhedral outlines typical of the genre. TM--04-6-9-3-8: White carbonate rock. Periclase (brucite) marble.. Displaying two sets/orientations of intersecting fractures. The earlier set/orientation attitude contains a darker subset,' with the aspect of a "crushed zone" (as per specimens TM-04-6-9-3-3, -4, -5-, -6, -7, above), and a relatively lighter subset. These two subsets. are subparallel to one another. This set is terminated abruptly by the second set/orientation attitude, .which latter is .manifest as an only-vaguely-discernible zonelfracture oriented: at an angle of approximately 90 degrees to .the trend of the earlier set. This later fracture/termination vaguely shows some apparent recrystallization features along its trend... This sample, otherwise, is a fairly "homogeneous" rock.. (Cf. .remarks on similar appearing periclase [brucite] marble under TM-04-6-9-3-9, below). TM-©4-6-9-3-9: This specimen is a KEY one. Consisting as it does of an exceNent ("splendid°, according. to SMA's subsequent more complete analysis) example of a periclase {brucite) marble. Principal. features (often clearly displayed, in superb fashion) include: "Original" periclase; as residual .cores of periclase, featuring well-developed ' euhedral crystal forms. ' Subsequent partial to apparently complete pse:udomorphous replacement of periclase by brucite. Brucite occurs. as radiating masses of eu-subhedral crystals (a "radial fibrous texture /aspect). The long dimensions of the fibres are oriented essentially perpendicularly to the` original outline/faces of the periclase crystal replaced/being replaced. Various "facets/degreeslextents° of this are displayed throughout the entirety.. of this specimen. Apparently without. any (recognized) preferred location(s) for the "occurrence /degree/extent" of the processes}. These features .texturally.. and mineralogically manifesting --..affording .clear evidence of -- the petrogeneticalty-key chemical reaction for the .formation. of periclase marble from precursorial dolomite:. CaMg(CO3)2 ---> CaCO3-FMgO+CO2. (Cf. H. G. F. Winkler, 1979, .esp.): The specimen overall is a white/very light grey .carbonate rock (marble). It features. a somewhat rectilinear system of fractures/ "recrystallized/healed crush zones", -with two 6-A GMC DATA REPORT 3 4- 8 Page s6/i2~ predominant sets recognized, intersecting with, one another at relatively high angles (ca. 60 degrees +/-). .One set consists of fractures on,the order of 1-3 mm in apparent width,. as viewed on the - largest specimen face; the other set consisting of fracture zones on the order of 4-5 mm in apparent width, as viewed on the same specimen. face. This specimen face is essentially rectangular in outline, with dimensions of approximately 6.5 x 4.5 cm. The fracture fillings/"veins" are vaguely "zoned", with: "darker/greyer" borders, and medial portions tighter, more. similar in color to the surrounding host rock marble. Associated .with both the white translucent-clear material, (calcite, texturally .present as a crystaltine mosaic) comprising the bulk of the carbonate rock/marble, and the greyish-clear .phase(s) of carbonate(.?)/+/-?? in the "veins/veinlets/crush/healed .zones", are dullish- white °blobs/patches": Such a blob/patch displays (variously) ablack-brownish-greenish- yellowish central "core" of .apparent ("residual/relict") periclase, surrounded peripherally by white-brownish-grey-greenish, "waxy"/semi-vitreous, generally tibrous, brucite. )n many cases the spatial relationships represent, essentially, brucite "caught-in-the-act" of , replacing previously-formed periclase. (Mineralogically and texturally manifesting .the petrogeneticapy key reaction:. CaMg(C03)2 ---> CaC03 + Mg0 + C02). Numerous examples, variously-well-developed/displayed, are apparent throughout this specimen.. Many are, indeed, truly "exemplary". Typically, (Cf. the somewhat voluminous original detailed laboratory notes, and accompanying drawings, of the specimen examinations by TCM, not .presented in this report.) In most places throughout .this specimen, the ratio (by visuat estimation under the stereomicroscope) of carbonate (catcite):periclasefbrucite is on the order of 60:40. The [atte~ abounds, as areas of filled/partially-filled. voids, "patches", "blebs", throughout the .specimen, within the "white carbona#e" as ,welt as the. °greyer", "veinlet" portions of the specimen. The fractures, the relationships among them, and betvreen them and the calcite and the perictase(brucite) occurrences, afford indications as to the geological history, timing, course of events, as related to the geochemical/petrogenetic episodes represented in this specimen, and the Arctic Chief locality overall. (Cf. as well, in this context, similarities. to other. periclase (brucite) marble specimens from this, and other nearbylstratigraphicaiiy equivalent locations sampled [as described above and below].) 'The fractures/crushed zones, with their associated recrystallized carbonate, +!-, material(s), appear to have formed prior. to (?) the formation of the periclase. This seems {ikely, since the periclase crystals .(and, significantly, their subsequently-replacing brucite} are apparently unaffected by these fractures/crushed zones, and also. occur with essentially the same/equal concentrationsffrequency within as wet! as outside these zones. And the likely relatively fragile//readily-deformed/obliterated radiating crystal habits/habitats. of brucite, as well as the. often. weft-developed euhedral outlines/shapes of the original periclase crystals, are similar/the same/identical within as well as outside these. zones of apparent structural disturbance/deformation and related/associated recrystallizatian. Likely they would have been distorted/damaged/obliterated had they existed prior to, or during, this fracturing. TM-04-6-9-3-10: ..Specimen features a number of readily discernible metasomatic/metamorphic "zones". These ail occur in the relatively small volume ~f this specimen. The dimension measured at aright angle to the .attitudes of the "zones" as .displayed on the. "best" specimen surface is 8.5 cm. This zoning seems to perhaps exemplify, the "primitive" type in a magnesian skarn (cf. Aleksandrov,1998 & etc., on zoning "in pipes and stockwarks in tectonically crushed zones in" .the envelope of dolomitic rocks around granitic contactsH). The zoning is manifest 7-A GMC DATA DEPORT 3- 4 8 page s7l12~ mineralogically, geochemicaliy, texturally, as well as visually. Note. some indications/evidence (viz. offsets, trends of mineral occurrences) of fraCturinglfaulting within this. specimen, which suggest (per SMA; see "references") perhaps a situation of "long-lived" tectonic/"crushed zones setting? fe. during the magmatic and post-magmatic stages. Although (per .SMA, esp. p. 4 in the 1998 book} .the nature and scale of the zoning. in this particular. specimen actually seem to suggest a situation of pre-skarn fracturing/crushed zone formation, which features became sealed during the formation of the primary metasomatic zoning. {seemingly as exemplified in this- specimen (?}. The "zones" featured in this specimen are here-labeled (solely: for purposes of description) and here-described, ,from. "left to right° across the particular orientation and face of this specimen :selected for description. The first zone ("An) consists.. of a white-light grey periclase {brucite) -marble: The major mineral.. constituents of this marble. are calcite and periclase (brucite), occurring as a crystalline mosaic. The periclase (brucite) occurrences are .often rather well-developed {some "ciassic~), nicely displaying the periclase "core-brucite "rim" relationships, etc., as noted in other marble specimens collected/ob:>erved at this sample location, as well as at other sites at the Arctic Chief. [Cf. remarks on similar-appearing .periclase [brucite]. marble under TM-04-6-9-3-9, above. See afro observations, comments, sketches, to detailed " laboratory notes (TCM), which: are. not included in this report.). Trace amounts of subequanfi sub-euhedrai crystals of a greenish-black semi-transparent mineral(s) are noted .which might (?) be spinet, or pyroxene {?j. One such observed is associated with a small. grain of a black crystalline material which might be magnetite (?), or The "bests such euhedrai crystal of a black mineral noted shows vaguely-defined striaelcleavage (?) subparallel to its long dimension, suggestive of a pyroxene. This crystal may well be twinned, as an apparently similar crystal lurks beneath, vaguely defined within the surrounding crystalline mosaic of calcite, .periclase: (brucite), etc., comprising the bulk of the marble. This crystalline -mosaic also features disseminated "very-very"-ffie-grained black "platy" (graphite?/magnetite?/phlogopite?/??) specks/grains, some associated with apparent "rusty" (hence iron-bearing?) material{s}. Zone "B" is a "forsterite, +/-?, calciphyre". It consists principally. of predominant .calcite (as a crystalline mosaic), and, generally (except where present in some concentrations, as °layers/bands/lenses/pa#ches/streaksn), substantially subordinate forsterite/forsteritic olivine. The zone. is "somewhat bandedn overall, and features darker grey,. }fighter grey, and yellowish-greenish "subzones">portions, as well as varying grain sizes {some discernible megascopicatty). Compared to zone "A°, zone "B" features a greater amount. of black vitreous crystals/aggrega#es, some of which are associated with patcheslmargins of yellow-brown material similar to that observed in zone "A" in association with black. crystals of (?). Also note some crystals (some apparently 6-sided} of clear vitreous aspect, with, patchy . distribution. of internal disseminations/"dustings" of a "very-very"-tine-grained., chocloate brown material.. AU set.. in the crystalline mosaic "matrix" of the predominant .calcite. The concentrations of greenish, black, and brown-dusted.- materials are most apparent as occurring in ill-defined .but discernible - "bandsn, which define the "banding" within this zone, occurring in subparallel aspect/orientation to the :major "boundaries" between "zonesA 8-A GMC DATA REPORT 3 4 8 Page 8s/12~ lie. marble, -then calciphyre, then forsterite; serpentine, pyroxene, garnet) in this specimen: These. "bands" are often-more like wispy patches, lenses, actually,. within this .zone "B". "Interbands" containing. more, or less, marble/calcite crystalline mosaic material occur as well; essentially by varying degrees of abseneedlack -- default, as it were -- of other constituents. The zone "B" vs. zone . "C" boundary, if indeed a "B-C boundary" actually exists as such, is "vague; perhaps illusory(?). Though the concentration of green mineral(s) increases from Zone "C° consists of a forsterite calciphyre, similar to "B" except for a greater proportion of °yellow-green" mineral constituent{s), principally forsterite. Zone "D" is light green in color with a elf! low tinge due to its increasingly forsterite-rich (veHow-green mineral)- content. becoming an essentials "monomineralic" zone though with scattered -black sub-euhedral o.~ague gCains ••- maanetite~.)_ distally from "C". At the distal from-"C"/proximal-to-zone "Fn t~ortion of this zone lie. "D"l. is a relatively thin subzone ~E") consisting of serpentine {+/- same forsteritel. developed ~ ^^ ~ i ly continuously along this "border/boundary" This is probably the "bottom" of zone D" if as seems not unlikelw the presumed source of the metasamatizing fluids was toward zone "F". (???) A "monomineraiic forst~erite" zone, per SMA(?). Subzarie "E" is light green, "waxyn in appearance, comprised: principally. of crystalline serpentine, with preferred orientations of the Tong dimensions of the prismatic-appearing crystals -- chrysotile, or perhaps antigorite (?) -- in growth positions (apparently), essentially perpendicular to the boundary with zone "F". It is highly fractured; with some white fibrous crystals (talc?!+/-?) also present, lining the fractures/seams. At the distal- from-"F" margin of subzone "E", a thin interval of "darker/denser"-appearing material of undetermined nature (representing depositional conditions mare conducive to a "massive" form. of crystallization of a serpentine mineral, perhaps antigorite?),_ occurs,. separating "E" from zone "p,; Immediately adjacent to!"below" this "basal° :serpentine-rich subzone. ("E") is a re{ativefy thin layer of red-brown. garnet, which has invaded through the black pyroxene zone ("F") adjacent to zone."D". This type of red-brown Garnet -- comprising theepredominanf mineral of zone "G" -- is seen in zone "F~, engulfing black pyroxene euhedra/masses. Zone "F" is dark grey to blackish, with areddish cast. It is comprised .principally. of. very .fine grained,. to massive, pyroxene, +/-, as a "skarn"..The pyroxene euhedra occur as black stubby prisms, with good cleavage displayed. Somewhat intermittently developed between zorfes "E".and: "Fn is subzone "P", comprised principally of phlogopite, +/- perhaps subordinate_ amounts of other material(s). Developed "below/subeven" with the serpentine .horizon of subzone "E", "P" manifests itself as pods/lenses of phtogopite. These podsllenses occur immediately adjacent to serpentine on one side, and to pyroxene (+/- garnet) of zone "F° on the other .side. In some places; observed clear micaceous materials may -- at least in part -- actually be talc (?), while in other (most) places the. micaceous .mineral is darkerfgreenish, and most likely phlogopite. An additional, rather intriguing, situation seems to present. itself in his particular portion. of the specimen: r n in hi eneral "horizon" include- o a ue hoses. (in minor/trace. Oth@r mmerats p ese t t s g p g p amounts). These include euhedral"octahedra"(?} of "brassy"-appearing opaque .material(s); 9-A GMC DATA REPORT 3 4 8 Page.. s9/127 perhaps chalcopyrite (?), or chalcopyrite after magnetite (?). Possfb(y (??) vaflerfite, tochilinite, etc..(?~?}, Same opaque masses feature ayellow-brown/"bronzy" material of pyrrhotite "aspect", but in direct. contact with .black material which may be/include magnetite (?!?). Some of this: bronzy material apparently has a "prismatic" crystal habit, variously developed. The opaques seem to be transected by garnet, +/- quartz(?), +1-carbonate(?), at .least focally. Elsewhere. in this same .general "horizon", some apparently prismatic (or, perhaps, , actually an "end-on" view of "layersn??) crystals of "bronzy" opaque material{s) are present, in direct contact with. (apparent} pyroxene .(magnetite??). In this particular occurrence, the "prismatic" aspect of the bronzy opaque. material might, aiternatfvely, actually represent manifestation of cleavage ors subjacent pyroxene crystals (perhaps undergoing alteration/replacment??). This "horizon" is essentially within the zone "F" vs. zone "G" transitionfborder, with boundaries irregular,. vague: As noted above, zone "F" contains appreciable/principally pyroxene, occurring as black stubby prismatic sub-euhedral crystals, showing goad cleavage. Might (??), per an observation by Ramdohr, the "bronzy opaque" material occur as an "encrustation" on pyroxene?. Asa "preferred" (for vatferiite/etc.) mode of .occurrence "as encrustations.:...:. associated with serpentine, .etc..::..." (Ramdohr). Pursuing thin thread .further, is the black "pyroxene" in contact With the bronzy opaque/valleriite(???) actually. pyroxene? Or, perhaps, magnetite? jln an association of garnet+/-quartz(?)+/-calcite+/-magnetite+!-valleriite/tochilrtfte+/-pyrrhotite ??j Zone "F" becomes decreasingly a discrete entity as admixture with/replacement by garnet, opaque minerals, +/-, is shown/represented through zone "G" to the distal edgeftip of the specimen. Zone "G" features a dark brown-reddish cast overall,. due to the predominant .garnet. Thin zone is, essentially, representative of "garnetiferous skarn". Pyroxene, magnetite, other opaque minerals, including sulphides, occur, variously, in subordinate/minor/trace amounts. Some '"rusty" patches. occur.. Copper "staining", apparently as malachite, +/-, occurs at the extre=me tip. of the specimen. Thus, in summary, a very interesting specimen. Essentially a "microcosm"of•the sequence: Periclase (brucite} marble. -- calciphyre(s), -- forsterite{+/-) -- pyroxene -- garnet+/-opaque minerals "zonation". .With calciphyres, forsterite, phlogopite, serpentine, opaques (perhaps. including vafieriite/tochiiinite??). Each in its "proper"/appropriate "position", .spatially. and genetically, petrologically and geochemically. (See Aleksandrov, 1998, ~ etc.). This specimen displays: Periclase (brucite) .marble Calciphyres, .with forsterite, +/- Metasomatfc zoning of the magmatic stage - Subsequent (partial, at least) effects of post-magmatic "alterations", through at feast the "acid stage" Minerals such as spfnel, phlogopite, serpentine; magnetite, chalcopyrfte, garnet, pyroxene - TM-tJ4-6-9-3-11 c This is a specimen with a number of aspects of magnesian skarn ,displayed in "microcosm": Blocks/fragments of apparent perfclase (brucite) marble, with runs.. of garnet, adjacent to pyroxene skarn material; then phlogopite +/- serpentine, .then forsterite, then -once ,again .back into- pyroxene skarn, followed in turn by another garnet rim, around another blocfdfragment of marble.. 10-A 6MC DATA REPORT- 3 4 8 Page 90/12 Phlogopite is very-well-developed, serpentine well-developed. Spines, +/- magnetite, +l-?, occurs scattered throughout the specimen. Note periclase and brucite, with. character and relationships as noted in other calcitic marbles/ calciphyres, from this, and other localities at the Arctic Chief. Interpretation of the observed overall relationships in .this specimen remains .somewhat ".uncertain"._ Do these blockslfragments represent. "nodules" of marblefcalciphyre, rimmed. by "reaction zones" (??) of garnet, as remnants within pyroxene skarn? Or might they be related to "apophyses" of °granitic"f? melt; as "tongue-like" fieatures intrusive into host rocks of carbonate.. (or previously-formed skarn material?) nature: With the pyroxene, garnet, phlogopite, serpentine, etc. observed being ancillary to this sort of situation. (Cf. TM-04-6-9-3-1, and -3, specimens with similarities to this one:) TM-04-6-9-3-12: Specimen (maximum dimension = 8.5 cm) contains a number of "zones", especially weft displayed across one of its faces.. in order, along a distance of 5.0 cm across this face, in a direction {"left to .right") perpendicular to the trends of .these. zones,. the relationships observed are as follows: From the leftmost edge of the specimen, a zone of reddish-brownish garnet, with .minor wide: calcite, 1.5 cm A zone of pyroxene skarn. Predominantly consisting of a relatively light green pyroxene, with minor/trace spinet, +/-?. This zone is on the order of 2.0 cm wide. A zone featuring predominant phlogopite, with .lesser calcite,- spinet(?}, "rusty" magnetite(?), talc (??). This zone is on the order of 1.3 cm wide. A thin zone (approximately 2-3 mm wide} along the rightmost edge of the specimen. It , consists principally of serpentine, some clearly fibrous, and minor "rusty" opaque material, presumably magnetite, +/- ?. I Additional observations: Black "very-very"-fine-grained, black ("flaky", at least in part) crystalsfmaterials occur disseminated throughout .the "pyroxene skarn" zone. The garnet zone has an aspect suggestive of an "apophysis"/tongue. (As discussed by Aleksandrov, 1998, & etc. Especially note a diagram depicting the development of zoning around an "apophysis"...:... -Also, on a larger scale, the similarity to known relationships at the HoltonfHol-Kol, North Korea, locality/deposit.) [As a further observation, it should be noted that there actually appear"to be a number ofi similarities between this Korean deposit and the Arctic Chief].. The shapelorientation of the adjacent pyroxene. skarn, as well as that of its adjoining neighbor, .the phlogopite, +/-, zone, mimicking as they do the shape/outline of the garnet zone, add to this "suggestiveness". Similarly, though not as well-displayed due to its location on the edge of the specimen, the shape/orientation of the serpentine, +/-, zone further. substantiates this "apophysis-liken impression: The. serpentine occurs intergrown with, and .likely from, adjacent. phlogopite of the - phlogopite +f- zone.,. Phlogopite occurs as well-developed euhedral crystals, light olive green to dark olive green in color, often with physically interleavedlintertayered other minerals. (viz. calcite?, +!-?). Given the nature, and "position", of these "zones", it might be speculated that a zone. featuring forsterite, +/-, might .well have existE:d "beyond"/adjacent to the 1 1 -A Page 91/127.. ~, GMC DATA REPORT 3 4 8 .serpentine!"phlogopite-serpentine"(?) zone observed in this specimen. TM-04-6-9-3-13: :Specimen is on the order` of 5A x 5.5 cm. It features. several "zones", especially welt- displayed onone of its relatively flat surfaces.. In order, along a distance of approximately 5.2 cm across-this face, in a direction ("left to right"} perpendicular to the. trends of these zones, the relationships observed are as follows: . A zone of "caleiphyre", on the order of 3.7 cm wide,. from .the Left edge of the specimen to the adjoining zone to its right. A zone on the order of Q.9 cm wide, consisting of pyraxene skarn, with minor associated spinet(?), +/-?. A zone consisting of serpentine, +/- forsterii:e, +/-?. It is discontinuously developed, :with a maximum observed width of about 1 - 2 mm. A zone appraximately 5A mm in maximum observed width, extending. to the right edge of the specimen. This zone consists predominantly of phlogopite, +!- associated: talc(?), +/-?. The calciphyre zonepresentssome indications of additional "subzoning"/banding'-within it, but this is rather "subtle", at best (especially under the stereomicroscope, on a rock .surface}. :The caliciphyre is made up predominantly of a crystalline. calcite mosaic (ie. a "periclasejbrucite] marble'), with lesser amounts. of associated "light", and "dark" minerals. These include forsterite, pyroxene, vesuvianite/idocrase(?), spinei, +/-?. Trace: quantities-of opaque minerals, featuring magnetite, +!- vaileriite?, +!- pyrrhotite?/pyrite?/arsenopyrite??-ioeflingite??, also are present, as lenslike/streaky occurrences. The calciphyre also features some. patches of .garnet(??}/+/- magnetite{??) -- as "rusty" .black .crystalline sub-euhedral grains. In association with the surrounding calcite mosaic some articular exam les of this materials are also Hated to be in close proximity to ~ N O traces/specks/crystals{?) of a bright blue-green mineral{s). The latter .range from sub-euhedral, are tabular-prismatic, .and appear/look.. "coppery". le., chrysocolia, +/- malachite, +/- azurite (?}. Or, sometimes seemingly "emerald- . turquoise colored". These "coppery" materials appear to be "vitreous-waxy" in aspect,. and are concentrated. in a °patch/lens/layers of thE; "rusty" black minerals. i -zone n its environ r Additionally, disseminated sporadically throughout the serpent ne a d s, a e some black-very dark brown vitreous crystals, ".not. uncommonly as euhedra/subhedra with six-sided ar eight-sided aspects. Some are "d~endritic"/"snowfiaky" in appearance, perhaps as crystal aggregates/skeletal crystals/growth forms. Remindful of manganese oxide "dendrites". Arborescent, overall. With many (variously) well-developed "six-rayed" branching forms displayed. Skeletal crystals/fiorms(?}; possibly borates{?); graphite(?), +[- ? TM-04-6-9-3-14• Specimen is 6.5 cm in width, as measured across the face' described here. Consists. of a number. of "zones", characterized far descriptive purposes principally by overall color, mineralogy, texture. As observed, from "(eft to right" across the face, these zones are as follows: 1. On the order of 6 mm and, .variously, less in apparentwidth, at the leftmost edge of the specimen: Greenish, consisting principally of phlogopite,. with".minor calcite, talc(?}. 2. Adjacent to zone 1. Approximately 1.1 cm in apparent width, variously,. and 12-A GMC DATA REPORT 3 ~4 8 Page 92/127 conforming to the shape of the adjacent zones on either side. Greyish, consisting principally of calcite!"carbonate", with some associated. perictase (brucite), and minor/trace. amounts of relatively. finer-grained "dark" minerals (spinet?/magnetite?/+f-?). A "pericfase (brucite) marble"/"calciphyre(?)". 3. Adjacent to zone 2. A "fens"P`tongue" of material comprising zone 5 occurs .within zone 3, occupying an apparent width of 1.5 cm in the central portion of zone 3. The apparent width of. zone 3 is 1.5 cm on. the "left" side of this iensltongue; and 1.0 cm on the other side of it. Zone 3 is comprised of "calciphyre", containing predominant calcite, with associated periclase (bructte}, and minor forsterite, +1-pyroxene. 5. The above-described zone 5 is made up of principally. of patches of reddish-brownish garnet, as well as some calcite, minor forsterite, epidote?/serpentine(?) and same blue- grey material which may be zoisite/clinozoisite!+/- (?). 4. Approximately 0.8 cm in width, adjacent 'to the "rightmost" .portion of zone.3, and: on to the "right" edge of the' specimen. Features a~-preciable pink and green (epidote?) and pink. .(zoisite?) materials, as well as "other" minerals, al! "dark", some opaque: Relatively -fine .grain size precludes definitive characterization (on a rock surface, with. the stereomicroscope) of the materials. comprising this zone. The overall "aspect" is ~uggesttve of "epidotizatfon"/ "alteration" of previously-existing material(s). Might zones. 2, 3, 4, 5 -represent "marblelcalciphyres" (2 and 3), associated- with (4 and 5} "veins"L"apophysis-related" features? After having been broken into several smaller pieces, this specimen shows same interesting "zonal" -- "transitional" -- "banded" aspects/features. Especially as regards the "cote-skarn"-like(?) garnet-epidote-opaque !"other" dark. minerals}-"blue-grey" zoisite/clinozoisite(?) association/"assemblage": TM-04-6-9-3-15: This specimen rather °comple'x". A "bodge-podge"/veritable "witches' brew°. "calciphyre"(?)/"marble"(?);"originally". Featuring (relict) "prograde"(?), as well as "retrograde" (ie. "magmatic stage", and "post-magmatic. stage"), assemblages. Minerals recognized/perhaps present are pyroxene (diopside?), garnet, magnetite, calcite, phfogopite, spinet(?), forsterite(?), +1-?. Patcheslienses/"apophyses"f"fingers" of pyroxeneldiopside(?), +1- occur. These rimmed with/outlined by reddish-brownish garnet, calcite, +1-?. The other minerals/assemblages' occur betweenlamong the several such "apophyses"(?) present. Apparently (?) representing a portion of what voas originally a magnesian .skarn, -with subsequent "retrograde" ("post-magmatic; late early-alkaline <---> acid stages", +/- --->?)..Illustrative, thus, of the general trend/sequenee of metamorphic and metasomatic events which were involved in the history of this. specimen. And, thus, by extension,. to the Arctic Chief deposit as a whole/overall (?}. .This specimen one of several collected at this sampling. site as representing. the "skarn" ..material(s) -- the "darker rocks", ie. -- of the "apophysis(es)° into/ associated.. with the hi r Ic t s t n viz. I Pci h re county /host ac s at oca e. li titer surroundin carbo ate marb a/ca g g ( p y ) y ["Representing", though not necessarily -- though of course "hopefully" - "representative" of such; ie.j 13-A page 93/127 AMC DATA REPORT 3 4 8 TM-04-6-9-3-16: Specimen is made up of a number of "zones", manifested by color, mineralogy,. texture: Illustrative of, "representing" (not necessarily "representative" of) the "sksrn"-like darker :material(s) occurring as .apparent "finger/lens/apophysis" features into/associated with the lighter-colored "carbonate" country rocks. at this locale. 3n the direction perpendicular to the "zones", the distance is on the order of 3.0 cm, across the face of the specimen. From "left. to right" a3ong this direction, the zones/materials. encountered are as follows: 1. Approximately 1.5 cm in apparent width. principal constituents recognized in a ..texturally "complexn rock mass include calcite. ("marble", ie.}, scattered phlogopite, olivine/forsterite(?}, +/-?.' Or perhaps better termed a "catciphyre" (?}. A dark "horizon"/"subzone" of pyroxene, +/-?, occurs in one portion ofi this zone, toward the. ..side adjacent to the adjoining zone "3". At the edge ofi zone 1, immediately adjacent to zone 3, is a thin "layer"/"subzone" comprised of principally of .olivine/forsterite(?}, +/-?. 2. Occurring vuithin the central. area of zone (`'1 ") is a "fens/patch" of "exotic/foreign" material, whicl5 is .designated. as "zone 2". It is "tinged" with/comprised at least in part of reddish-brownish. garnet, and. epidote(?}, as -- apparently(?) -- some sort of "vein/replacement" material(s). 3. About 1.0 cm in apparent width,. zone 3 is a light greyfwhitish "band", consisting: predominantly of calcite ("marble", ie.), with trace amounts of scattered "dark" materials}. A thin, discontinuously-developed "subzone" rich in phlogopite, +/-, occurs along the margin of zone 3, adjacent to zone 1. 4. Qn the :order of Q.5 cm in apparent width, zone 4 is made up predominantly of phlogopite, some calcite, +/-?, as a "dark bandthorizon" in the specimen. 5. Occurring along the "rightmost" edge of the specimen, zone 5 is essentially a thin "rind"/"skin" of either weathered specimen surface,. or, perhaps, vein-related/alteration material(s). The materials} have abluish-greyish hue, -with indications of vitreous.. aspect, perhaps also displaying some prismatic .forms. TM-04-6-9-3-1~: Specimen is a porphyritic .igneous intrusive rock,. apparently, of "intermediate" compasiiion. Representing a dike, perhaps "late"!"after" (?} the metamorphic/metasomatic activity responsible: for the formation of the Arctic Chief. deposit {??) [Cf. "References" section of this _report.]. Or, alternatively, perhaps at some, likely "later", stage during the formation of ibis deposit. in either. case, this. rock perhaps -- likely? -- crystallized from a melt related to, or a part of, the `°main magma/intrusion" responsible .for the metamorphism/metasomatism at the Arctic Chief locality, with attendant formation. cf this ore deposit. [Cf. other remarks by, the authors elsewhere.. in this report.].. This specimen features phenocrysts of zoned sub-euhedra! plagioclase (with some .included - "iron-affected" [ .Viz.. "magnetite!+/-?".] core and marginal- areas. [Much. "magnetite" began to crystallize late in the crystallization of plagioclase, as well as during subsequent matrix-solidification.] Such plagioclase is the predominant phenocryst miners! present,. with 14-A- GMC DATA REPORT 3 4 8 Page 94/127 subordinate amounts of quartz {eu-subhedral, and often somewhat broken up). Also noted are a .few scattered subrounded "lithic fragments"!"inclusionsn {"cognate"?), containing, variously, plagioclase, pyroxenelamphibole(?), quartz, magnetite. Also present are trace. amounts. of "micaceous material" {likely "biatite")?lpyraxene, amphibole? subhedra, of similar size to the phenocrysts, which perhaps represent portions of "relictidlsaggregated° lithic fragments. The groundmass of thin specimen is fine-grained, grey-green iin color, featuring plagioclase sub-euhedrai crystals, set in a surrounding matrix of quartz(?), magnetite(?), +/- another silicate. mineral which may be amphibole (??) andfor pyroxene{??). This matrix appears to be too light in color to contain appreciable amounts, if any, of such mafic silicates, however. Thus, .rather, perhaps a matter of "dusty" quartz!+/-, with finely disseminated opaque{s) mineral(s) -- viz.. magnetite, +I-. Some potassium .feldspar might. also be present, as matrix material, andlor as "micro" phenocrysts (??). i~owever, this is difficult to ascertain with confidence, using only a stereomicroscope on rock surfaces. This .specimen is m©~erately fractured, and "veinedA. The .fracture-fillingalveins feature a thin medial. zone, generally dark/black {magnetite?), with adjacent borders made. up of white material(s), perhaps ~ quartz?!carbonate?!feldspar(s)?. `TM-04-6~g-4-.. .,... The COlleCted specimens from this locale include carbonate racks ancf "skarn" material(s). Three of the Tatter "-17-A, B, C" feature "skarn" materials and "ores". These specimens are from outcroplrubble-crop, at a high- "bench" location, with -- at present -- not much directly above the sampling area except air,. birds, aircraft, etc. to have contributed "significantly out-of-place° material to these samples. (Bulldozers, etc. excepted,. of course.) TM-04-6-9-4-1: An example ®f periclase (brucite} marble. This is a somewhat weatheredlaftered{?) specimen. Rock contains predominant calcite, periclase (brucite), and a distinctly rninor/trace amount of disseminated dark-black materials}, probably at beast in part. magnetite {note "rustn), though some might be graphite{?). The. "pock-marked" weathered surfaces are of interest as regards recdgnitionf identification of rack constituents. Much useful information to be gleaned from scrutiny of "rusty° surfaces. periclase (brucite). and calcite are present in essentially subequat amounts, intergro~vn throughout .the specimen. .Comparisons with observationslcomments regarding similar-appearing specimens elsewhere at the Arctic Chief suggest not at all dissimilar rocks. Of particular interest in this regard are comparisons with samples from TN(-Q~-6-9-3, & -5, locatians, ~rhich are just across the Arctic Chief (west) pit entrance cut, to the "northish" of this "-4" locality. Carbonate, and Other, rocks, apparently/essentially "on-trend across. the pit entrance cut here. TM-04~-6-9-4-2~ Specimen is an "interestirtgfi one. A combination of periclase (brucite) marble and "skarnA material o i p rt ohs. ~~fith apparent chalcopyritel+!-? disseminated -- in fair amount -- v~ithin the carbonate 15-A ~ 6MC DATA REPORT 3 4 8 Page 95/127 rock adjacent to the skarn material The marble apparently. having' been invaded by sulphides, featuring chatcopyrite, +!-..galena(??), +/-?. The marble is comprised predominantly of calcite and periclase (brucite), with some disseminated pinkish-light brownish euhedra which may be spinel(?), andlor "flourite"(???)/+/-?, A "banded'/gradationaf contact/intercontact exists between marble and "skarn". In part at (east along "seams/fractureslshear zones"?, Some evidence of "internal` shears/slip surfaces/slickensides/seamlets° withinlthroughout "skarn" as well as marble. "skarn° consists of pinkish-brownish garnet, sulphide minerals (disseminated/semi- concentrated; chatcopyrite?f+/-?), calcite, quartz(?}, +l- trace of "epidote-like° coloration here and there, +/-?. One "pod/lens" of "skarn" seemingly occurs as an "offshootltongue° from the banded portion, into the adjacent marble. The weathered surfaces of this specimen afford supplementary information/evidence regarding mineralogies, textures; structures. TM-04-6-9-4-3: ` A Specimen featuring "banded skarnA adjacent toffinvading" periclase (brucite) marble. Quite similar to specimen TM-04-6=9-4-2 {cf. above}, Marble predominantly comprised of calcite and periclase .(brucite), with same disseminated sulphide (chatcopyrite, +/-?) mineral{s), +/-graphite?, +/-?. This marble is- quite. similar to that at other nearby localities elsewhere at the' Arctic Chief. (viz.. TM-04-6-9-3, - 5). "skarn" consists of pinkish-brownish garnet, pyroxene, sulphide mineral(s) -- chatcopyrite(?), +/-? -- calcite, black opaque material(s)/magnetite(?), +/=?. TM-04-6-9-4-4: A large (hand-size) specimen, broken into three pieces (which fit back together like- pieces of a jigsaw puzzle). Displays "bandingn,overall, in varieties of greys, black,whitish; .pinkish-brownish. Piece #1. The largest piece. Comprised of a number of "layers/bands°. Layer "A":.White-grey periclase (brucite) marble.. Consisting of predominant calcite; and subequal (periclase (brucite). Compare with other similar. marbles at nearby locations at the Arctic Chief {viz. TM-04-6-9-3, -5). There are trace amounts of black material(s) -- magnetite(?), graphite (??), +!-? -- disseminated throughout, often in "pockets" of ~ concentrations, and/or along "seams° within the rock. Also scattered eu-subhedral crystals (tetrahedrons?, +/-?) of pinkish-greyish-brownish material- (spinet?) disseminated in this. Layer as well. -Trace amounts of sulphides (chatcopyrite?) are 'noted; "smeared out" along a "seam" (a "mini°-crushed zone) tthealed" with recrystallized(?) .calcite. Layer "B": A band. of "darker" materials,. adjacent to "A". Comprised of black mineral(s) -- pyroxene?, magnetite??, +f-?, pinkish-brownish vitreous ..crystals/masses --garnet, +/-?, calcitelmarbie??. Some "hematitellimonite° like material(s) is/are associated with the black mineral(s), as well as along "mini-seams" across the rock, subparal{el to the "banding". Layer "C": A thinner band adjoining. "B°. Composed of somewhat more coarsely-crystalline calcite, perhaps due to recrystallization along a"seams(?) Trace amounts of pinkish- brownish euhedral (tetrahedral?) crystals. (spinel?/or??} occur sporadically within this ..band. There is also occasional sulphide(?) material(s); as well- as; more commonly, some' reddish very-fine-grained crystalline material which mighfi be hematite(?)/+f-?. Layer "D": Adjacent to "C°, this is another "darkM band, similar in :aspect and thickness to .layer "B". It ties subparallel to the other bands in the specimen. Layer "E"; Adjacent to "D". This a lighter band, made up principally of a .periclase ~ (brucite} marble/"calciphyre"(?}, similar texturally .and mineratogicatly to "A ; but -with 16-A GMC DATA REPORT 3 4 8 Rage 9x/127 a somewhat greater proportion of "darker" constituents. These batter present as dark grey or -black sub-euhedra (pyroxene?, magnetite?, traces of sulphides. (chalcopyrite(?), perhaps galena?? and/or molybdenite(???), +l-?), disseminated throughout the surrounding calcite and periclase (brucite) principal constituents. Piece #2: Adjacent tofcontinuing from Layer "E". Layer °F": Essentially similar. to the descripti®n of "E", above.. La er "G": Next to "F". Os a whiter band,. similar to the material described as Layer "C". Y " above. Like ~t, "G" ~s a somewhat -more-coarsely-drystalline interval .than the marble/ calc!phyre" .bands observed elsewhere in the specimen. Relatively "pure", preponderantly crystalline calcite, though with some :concentrations of sulphides, +/-?, especially along the margins of this banditayer. Layer "H": Adjacent to "G",.'.this is another band of "intermediately-darker" (?!?) aspect, somewhat similar texturally and mineralogically to some of the other bands 9n this specimen, such as Layer "E" in particular... Layer "I": Adjacent to "li", this is a lighter band, featuring much less in the way of "darker" minerals/materials. It resembles Layer "A" rather closely, and is the final "Layer" so-designated in this specimen. It is a periclase (brucite) marble!"calciphyre"?, consisting .principally of a crystalline mosaic of calcite and associated periclase {brucite). Note especially features in evidence on the weathered surfaces of this specimen. Cf. other specimens from elsewhere at the Arctic Chief, especially TM-04-6-9-3, -5. Trace amounts of disseminated dark opaque grains are observed, likely magnetite ,(note. accompanying "rusty" haloes. Also note some pinkish-brownish sub-euhedra. (tetrahedra?; _ spine!?), as well as perhaps same graphite(?), disseminated throughout this layer. Piece #3: Comprised of some of the "bandsllayers" described in the other two pieces of the original specimen.. This Piece #3 contains Layers "E, F; G, H, I ", per the foregoing observations. The weathered surfaces of this specimen offer a wealth of euidencefeffectsfinformation as to textures, mineralogies present. Studied in conjunction with freshly-brakes surfaces, collectively much is available to be gleaned from this specimen. TM-04-6-9-4-5: ". r h vin in e i e s I' 'n tr ect s mean S ecimen a white ericlase brucite marble. Contao s ass g g y , p P ( ) features which apparently are "healed"/recrystallized "crushu-zoneslfractures. These are made up of clearer, coarser-grained calcite than occurs within the crystalline mosaic of the marble per se. Cf. similar marbles,- etc., from other nearby. sample localities at the Arctic ~ Chief -- viz. TM-04-6-9-3, -5, etc.. The weath~:red surfaces are informative as to texture and mineralogy of this specimen.. In particular, the presence and nature of the- periclase (brucite) and the calcite,. as well as .the relationships among them, are well-displayed (as, in fact, they are wi#hin this specimen as well). Trace amounts of fine-grained .black material(s) -- .magnetite(?); graphite(??), +!-? - -are disseminated throughout the. specimen. The veins"!fractures in the specimen are essentia8y "linear", and intersect ©ne another at various angles, in a relatively (to other observed specimens at the Arctic Chief) widely- spaced networtc. TM-04-6-9-4-6: This specimen is quite similar to TM-04-6-9-5 (which. cf., aboveJ, but with a more closely-spaced .network: of "veins/fracturesfhealed crush-zones". A periclase. {brucite) 17-A GMC DATA REPORT 3 4 8 Page 97/127 marble, with predominant calcite and periclase {brucite}, as well as trace amounts of - disseminated black material(s), .which may be magnetite(?)/graphite(?)/+/-?. The weathered surface of this specimen is not. as well-developed as on some other similar specimens, hence the informative "hummocky topography" is not as promir:ently evident here. TM-04-f -9-4-7: This `specimen, together. with the ..nearby TM-04-6-9-4, -5, -6 specimens, essentially represent "minor variations bn a common theme°, as it were. Alt are rather similar in general appearance, aspect, composition. This ("-7") specimen, however, features amore- closely-spaced network of "veins/fractures/healed. crush-zones" lie., a` greater/higher °fracture density" than any of the others). perhaps interestingly/informatively(?}, in the context' of the foregaing, this"specimen alsa affords, .perhaps most clearly of the. tour, a quite well-developed, .most illustrative,. example of the periclase/brucite, and associated calcite, typical of these periclase (brucite) marbles present at the Arctic Chief. The. grain-sizes are relatively .larger, here, in this .specimen.. The minerals are well better)-developed, their inter-relationships (more)clearly-presented. All fairly evident, both on weathered, as well. as freshly-broken, surfaces,_ while also displayed quite clearly. within the specimen. TM-04-6-9-4-8: This specimen is a light grey periclase (brucite} marble. Consists predominantly of .a crystalline mosaic of calcite and periclase (brucite), with trace amounts- of black material(s). -which may be magnetite(?), graphite(?}, +/-?. This specimen is similar to others from nearby localities sampled at the Arctic Chief (cf. in .particular TM-04-6-9-3, -4, -5): Some relatively vague indications of "crushed"/"heated" zones. throughout .this specimen, manifest as somewhat. well-defined linear features, .although well-developed...networks `of intersecting "veins°/etc. are not readily apparent. Moderately-developed weathered surfaces display textural, mineralogical, structural features, in complementary fashion to the .freshly-broken surfaces elsewhere on this specimen. Not quite the sort of "hummocky topography" as developed on .other specimens of similar character, but akin to tt. TM-04-6-9-4-9: Light greyish. periclase {brucite) marble. Featuring some especially noteworthy examples of the periclase-brucite. relationship, evident in umistakeable fashion.. With. some fine examples, .variously, of .periclase crystals; remnant "cores", with fibrous ,crystalline brucite "rims/whorls" adjacent to/surrounding/pseudomorphous after/replacing the periclase. Att within a "marble-texturedA crystalline mosaic consisting. of subequal/ predominant calcite as .well. As per a comment of SMA, this is indeed a "splendid" .example of the periclase (brucite) marble lithology: With alt the implications -- petrogenetic, geochemical, geological -- .pertaining thereto. . The general "greyish" cast. of this specimen likely is due to the significant (though "trace" amount, ..overall) .abundance of very-fine-grained black. {graphite?/magnetite??/+/-?} materials} disseminated throughout. Not in even a minor amount, or so it appears, yet quite evenly-destributed within the specimen. There is at least one "pocket» of sulphide .minerals {chalcopyrite?/pyrite???/+/-?), ` with some at least siisplaying aspects of eu-subhedrai habit, within the periclase (brucite) marble"/"rock-forming .minerals" crystalline mosaic. Suggestive, perhaps, of an "early" formation, likely attendant to -the metamorphism of the assemblage, Perhaps due. to the. presence, pre-metamorphism (cf. as well ..the.. apparent(?J presence. of .ubiquitous every-fine- grained "graphite"(?J throughout. the entire specimen) of an isolated remnant of pre- 18-A GMC DATARE~ORT 3 4 8 Page 9x/127 ,existing, likely ,biologically derived, organic matter? le. "organic" material(s) in a precursorial carbonate- sediment, etc., etc: ? Several excellent examples of periclase-cored, brucite-rimmed, eu-subhedrally-outlined pseudomorphous °crystals" occur -not tar .from this "pockeUpatch" of sulphides. gAccident"........... °coincidence":...... or incident".:....... Several subparallel semi-linear/planar. "seams/veins" transect #his specimen. These occur in afairly-widety-spaced "network" of intersecting fractureslshears/"healed crush ....zones". Though compared to other similar samples from elsewhere at the Arctic Cttief, the "fracture. density" apparent in this specimen might best be termed "moderate°. On weathered surfaces, there tends to be a "greenish. cast"..associated with materials. presently. occupying °core" positions in/within periclase --> brucite "composite crystals". Perhaps aweathering- phenomenon/product? .Possibly related to a .ferruginous componentof the original periclase..:.....and/or the replacive brucite? Or...:.. ? Atl-in-all, an exemplary specimen, in a number of ways. TM-04-6-9-4-10: A largish specimen, comprised of two types/colors of periclase (brucite) marble, one a dark grey and the other a "whitish" color. The two varieties adjoin one another with a rather: welt-defined/sharp contact, of apparent sedimentary nature. There is the decided impression of original differences in composition (+!- texture) between these two variants. (ie. a "bedding contact")..Although some sort of "front"-type. contact .related to metamorphism/' , metasomatism is another (though unlikely, in my opinion) alternative interpretation. The "white/lighter" lithology closely resembles. similar-appearing periclase (brucite) marbles encountered at the Arctic Chief {cf. TM-04-6-J-3, -4, -5, etc.), Some. fine examples of the. mineralogies and textures in terms of the predominant calcite and periclase {brucite). phases present, are .evident herein. These relationships. are also well-illustrated on weathered surtaces of this specimen. A particularly illustrative "veinlet"/fracture of linear/planar aspect transecis the darker lithologicai variant,, abutting againstltrending into the lighter adjoining. "layer" at essentially 90 degrees. This feature. appears to continue oh through the lighter material, on to the "diets!" ..weathered specimen surface, on which. a "rusty" zone is manifest, associated with a series ©f dark fine-grained "specksn (presumably iron-rich; sulphides? and or magnetite?; or....?). Such "vein/fracture"-associated zones at the distal (from the darker-colored rack variant} end of the specimen feature a "string-of-beads"-like array of black crystals (magnetite?/+/?), with "rusty" portions/subzones/margins/adjacent host rack-staining/ alteration effects manifested. One of these. "effE:cts" being .apparent staining/alteration. of nearby/adjacent minerals. This especially notably .affecting "rims", .and/or "cores" of the periclase --> brucite assemblage/materials, which appear to have been particularly susceptible to such °iron-staining". Perhaps essentially merely a matter of physical adsorption, etc., of iron-.rich. fluids by, especially, the generally-fibrous brucite.. Though formation of "iron-rich brucites" due/related to to pre-weathering phenomena are also a possibility.. This "string-of-beads" occurrence is unique. to the .fracture/crushed-healed zone best developed at the distal end,of the specimen, and best-displayed on the weathered surface there. The "white" rock variant being elsewhere/otherwise essentially free of other materials, containing only relatively little/trace amounts in the way of disseminated dark/black material(s) --_ graphite?, +!-?. Appreciable similar-appearing very-fine-grained dark/ black material(s) occur{s) in association with. the above-described fracture/healed-crush- zone. Other crystalline ..material(s) of "rusty" appearance also is/are .found in this zone, though, again, this perhaps is actually representing "iron-staining"(?). 'Or another 19-A GMC DATA REPORT 3 4 8. Page 99/127 mineral/phase:. ???, This "crushed .zone" features more coarsely-crystalline calcite, suggesting a °seff- healing/recrystallization" genesis, attendant to fracturing and recrystallization during and/or :.subsequent to metamorphism (cf. analogs in similar fithologies at other nearby Arctic Chief. locations). This' zone persists in linear-planar attitude across. the °white" lithology, manifest, for the most: part only vaguely, by a trend of sporadic "rusty" specks/material(s), ..until "emerging" at the "distal" end, clearly evident on the weathered. cock surfaces there. This zone crosses the "border/contact" between the .lighter and the darker lithologies, persisting across the latter to the edge of the specimen. More clearly evident in the darker lithology, due to the contrastingly white calcite of .which .this zone is presently comprised. It immediately/abruptly changes character upon entering the white lithology. Seemingly swallowed. up/disappearing, as it were, .within this new host rock of somewhat less-dissimilar nature to itself, as compared with the darker lithology. The darker greyer lithology owes this .aspect principally to the substantial.(verging on being a "minor", rather than a "trace" constituent) amount of fine-grained. black material(s): of "graphitic"(?) aspect disseminated/scattered throughout this. rock. type, along {principally, if not actually totally) the margins/boundaries. of the rock-forming ..minerals (viz: calcite, and periclase [brucite]}. There is also an impression. of somewhat "greyer" crystals of calcite in this "darker" lithologic variant. Though the amount,. and widespread dissemination, of the discernible .inter-crystalline "graphite"(?)/+/-? materials} in itself seems sufficient/quite adequate to "explain" the relative darker color/cast of this lithology. Presumably representative or an original sediment/sedimentary rock. with an appreciable carbonaceous component. [Perhaps less magnesium-rich as wet!? With possible implications with respect to "magnesian-skarn" development?? Is the periclase (brucite) component: of this "darker" lithology less .than, equal to, or greater, than in .the "whiter" lithology? Good/interesting question......... (?!?}. Though the "appearance" under the stereo-.microscope suggests subequal proportians of the twa principal rock-forming minerals in this darker lithology (in which the viewing constrast is perhaps no better or .worse, essentially, than it is in the.' lighter lithology(?). [Perhaps a useful. subject for some thin-section work?] TM-04-6-9-4-~ 1 : A white .periclase (brucite) marble. A "foot"-specimen; ie. somewhat .larger than merely the run-of-the-milt "hand" specimen. Chosen thus for purposes of serving as a "reserve" specimen, for- possible future work. "Representative" of other "white marbles" of similar aspect in this portion of the Arctic Chief. Calcite and periclase {brucite) the principal rock- forming phases, with .associated. trace amounts of dark/black .material(s) ["graphite"?!+/- ?] somewhat irregularly disseminated throughout.. TM-04-6-9-4-12: Another "foot" specimen. Mostly alight-grey periclase (brucite) marble,: with one end of the specimen an_apparentlycoarser-grained white. periclase (brucite) marble: A relatively .sharp .contact exists between these two. lithotgic/color .variants.. Perhaps. most likely representing asedimentary/bedding contact- {?). Or some sort of "front", due: to metamarphiGmetasomatic activities (???}. One .obvious fractureJseam/crushed-zone (?) cuts the grey rock, at an other-than- subparallel angle to the white-versus-grey rack contact. The. grey .rock has some lenses/pods/wisps of coarser-grained "carbonate" rocklmaterial(s) in it, here and there. Not as white as the "white marble", but lighter, and coarser-grained, than the "grey" marble. 20-a GMC DATA REPORT 3 4. g Page 100/127 r le c ntains a roximatel sube ual ro onions of the two rincipal rack- h ma b o p T whrte e q p p y p p formin minerals, calcite and (nicely-developed and displayed). periclase (brucite}. Trace g amounts of "very-very"-fine-grained black (graphite?/+?-?) and amber (spine!?) grains are disseminated throughout the. white marble. The grey marble shows even better-developed periclase .(brucite) features, with excellent examples of .brucite "cabbage head" rimslpseudomorphs, periclase cores, etc.: Some especially. nice examples occur on weathered surfaces of the specimen. This grey rock is also. quite similar to numerous others from nearby localities examined at the Arctic Chief. The: rock- forming calcite in this grey marble here is .somewhat finer-grained than its counterpart in the associated white marble in this specimen. The amount: of dark-black material(s): disseminated in this grey variant here is a bit/somewhat -- though not all that much. -- greater .than in the associated white marble. TM-04-6-9-4-13: A hand specimen. Featuring two variations on the theme of periclase (brucite) marble. One. a "white", coarser-grained, more "massive" variant. The other a "less-white°, finer- grained, less "massive"-- "bedded/layered" (structa~rally?} -- variant. The corrtact/bordeNinter-relationships between these two somewhat: ambiguous in` hand specimen. The less-massive type contains/is cut by a relatively-closely-spaced network' of (apparent) fractures{?}, intersecting one another at various tow-higher angles (cross- bedding??~, Both variants are well-developed periclase (brucite) marbles,. similar to others from nearby localities at the Arctic Chief.. Weathered surfaces show .this best on the "white" variant here, while the similar relationships are even better-displayed by the other. variant; both. on weathered and "fresh° surfaces. TM-04-6-9-4-14: A large hand (a "semi-foot"?) specimen. Mostly weathered surfaces all around on this particular specimen. Rock a whitish periclase (brucite) marble/ "caiciphyre"?, featuring a podliens/inclusion/(?) of dark grey-black material(s). [Possibly of .organic composition, origin? le., perhaps.."faunal/floral" remains?j The black material(s) might{???), alternatively, be "skarn" -- ie. garnet(?), +/-pyroxene(?), +f-?'. The weathered- surfaces of this whitish rock display, rather/fairly well, the usual features. representative ofi the periclase (brucite) presencelrelationship, simil~rx to other specimens .from nearby localities at the Arctic Chief. TM-04-6-9-4-15: A hand specimen. A .grey-whitish periclase (brucite)' marble/°caiciphyre°{??}: All surfaces are moderately weathered. Some "humrnocky topographya is developed. The weathered surfaces :manifest quite well the relict cores of periclase, and the surrounding rindslshells/rims of brucite pseudomophously replacing originally eu-subhedral crystals of periclase*. As noted commonly at this, and other nearby localities at the Arctic Chief. ['Often featuring an "oolitic" aspect. Which ought to be kept in mind when studying features on weathered surfaces. While of course "true" oolitic forms do in fact occasionailylnot infrequently occur in carbonate rocks!] !Vote a set of intersecting fractures transecting the specimen, atfwith a moderate spacing/density. Note also suggestions of banding/layering subparallel to the short dimensions of the specimen... Some portions {"bandsflayers", ie.) of the specimen are "whiter", others less so, {"greyish", or "plnkishn). A pinkish hue is not uncommon,: and somewhat more. apparent in 21-A GMC DATA REPORT 3 4 8 Page to %127 calcite-rich. portions of the rock, due to the darker-greyish material(s) associated .with 'surrounding/adjacent network of fractures.: Some of the. "pinkishness" may be due to "rusty" effects. of weathering/+/-?. TM-04-6-9-4-16: This is a "large" hand specimen. Features two varieties of periclase (brucite) marble. One a lighter grey, more. massive type, the other a darker grey, more °Iayeredlbandedlbedded" variant.. The contact between the two is fairly-well defined, and is in subparaflel orientationlattitude with respect to "layering" in the darker variety. The specimen overall seems .somewhat "heavyldense" for its sizefdimensions(?). Avague impression of a certain "unusual .heft" to it (?). - The tayeringletc.(?) of the darker variant reflects original bedding, apparently/probably. Perhaps(?) also a .result of "less intenseJless thorough" metamorphism (+/- metasomatism) of this portion/lithotogy of the specimen.. This darker variety appears to captain a greaten proportion of "carbonaceous/graphitic"(?) material. Both variants are akin to perictase (bructte) marbles .from other nearby areas at the Arctic Chief. Specimen too large far much examination with the stereo-microscope,. while further breaking might destroy some of its "mega" aspects.. Thus "reserved as-is" for possible future work. TM-04-6-9-4-17-A. - Specimen one. of three (-"A, -B, -C") from the same sampling. site at this "-17A locality. This "-A" specimen an example of "banded skarn". Featuring pyroxene (?), magnetite- bornite-phlogopite-chlorite?-talc?, .calcite (pinkish white), garnet.. (pinkish-brown), +/?. Pyroxene now strongly altered, with .products including "amphibole" (actnolitel tremotite}, "green micaceous." material, likely phlogopite (+1-?), +/-?. Some fibrous "serpentine" also. hated. "ReNci/actual" pyroxene is not readily apparent,. but there .might well be some remnants,. masked by/associated with the alteration. products ubiquitously present with "pyroxene-like" material Some of the "green micaceous material(s)" is/are a lovely bright to deep green (likely phlogopite [or "clintonite, "mariposite/fuchsite"??J). Not infrequently "fibrous" margins/ edges of this. matertal .are variously well-developed ("serpentinefchlorite/talc" ??). The calcite and garnet .are intergrown (sub-euhedral} in "pockets", with surrounding "green micaceous material(s)", magnetite, bornite (some of which is also intergrown with calcite and garnet). Magnetite and bornite range sub-euhedrai throughout the specimen.. The "micaceous" minerals are generally well-developed sub-euhedra intergrown with, magnetite, bornite, etc. Also .possibly(??) some hematite(?}, .quartz, +/-?, associated in very minor - amount with the calcite-garnet, +/-?, "pods/len es/vugs(?)". Much of this specimen consists of .intergrown "green. micaceous°-magnetite+/-bornite. Note an unusual "dull brownish-blackish sub-ei~hedral o ague phaselmateriat" in one place. associated with "green micaceous" mineral). calcite. magnetite {which is not "rusty/oxidized"). This "unusual/dull'-appearing material resembling perhaps an oxidized/weathered/altered magnetite {but note the presence of the adjacent "fresh" magnetite). This material somewhat resemblesfha5 some intriguing similarities to a specimen labelled "valieriite". presently on display in the Yukon Visitor Centre display of mirierals found in the Territory The site of this material in thepresent sample is on one edge near ong of the tins" of the specimen The "valleriite~~~'~" is intergrown with bright "green micaceous" mineraUmaterial. for the most part as well as in part intergrown with adjacent I magnetite +/- bornite in the one not d "occurrence" 22-A 6MC DATA REPORT 3 4 8 Page io2/i2z This specimen, TM-04-6-9-17-A, should be compared with the descriptions of its (complementary) "compatriots", "-17-8, -17-C". Especially with regard to the presence.:. or absence of pyroxene in each, vis-a-vis magnetite. Also as regards the green micaceous mineral(s)/materials(s), .etc.' TM-04-6-9-4-17-B: .Nand -specimen of "ore". Made up of bornite-chalcopyrite-magnetite-"skarn"-, +/_?. Some "rusty" areas on specimen surfaces. Apparent relict black pyroxene (note cleavages) occurs, though in large .part altered to "masking° green. micaceous material(s), +/-. (Cf. sample "-A»). The larger, more "flamboyant" crystals of "green .micaceous" mineral(s) seem fo be ..associated with. the "ore" minerals. While the smaller, somewhat. 6ess-"spectacular" mica- like materials tend to be found/occur in association .with the "skarn"/pyroxene, where lesser amounts of "ore" minerals are in relatively closf; proximity {?). In this. latter -- ie. the pyroxene" - "skarn" areas --, the mica-like crystals are smaller; thus (?) appear "lighter" in "greenishness", with. perhaps(?) an additionat mineral (white,: "very-very- _ fine-grained", perhaps calcite?/ 'amphibole?/ serpentine?/ diopside?/ talc?? #orsterite???/+l-?. Though this may merely represent an optical "illusion" due to smaller grain size(?}. This grain size effect perhaps the result of "granulizationn due to pulverization. .attendant upon tectonic/structural deformation? Using only. the stereomicroscope, much of the foregoing remains somewhat. "speculative", at best. The "skarn" portion of this specimen grades into a zone of more coarsely-grained "mica- like" material(s) + relict pyroxene + magnetite +chalcopyrite +bornite, intimately intergrown, with some scattered small vug-like patches of very-very-fine-grained euhedra of calcite/"carbonate" of light buff colour (ankerite?/siderite?. Mica-like material is "retrograded/altered" to .talc(?) and/or serpentine(?), +/- chlorite (??}. .Minor amount of brownish-reddish garnet, eu-sub-anhedral in aspect, occurs sporadically distributed within the "skarn" material Brownish carbonate -- calcite?; siderite?; ankerite?) -- occurs, similarly, in the "skarn". Such carbonate also occurs, as more well-deVelaped ..crystals,. in association with "ore", especially .magnetite. Haw much apparent "pyroxene" is actually magnetite (with cleavage), at feast in parts of this specimen? The "green .micaceous" looks more (ike "tats"(?), for the most, part, in this ~-B" specimen, than it did in specimen "-A". "Green9 phlogopite --> talc and/or serpentine {note .fibrous edges/margins of "mica-like" crystals), as "retrograde" andfor "alteration" effects/results? Magnetite in this specimen is euhedra!-subhedrat, massive; .bornite .sub-euhedra!; chalcopyrite is rarely better than' anhedraL This specimen is "rustier" .than "-17-A". The "rustiness" makes the search for "valleriite" rather difficult. ONy the very occasional possibility was noted; -- -a11 rather "dubious" This .specimen, TM-04-~-9-17-B, should be compared with the descriptions of its (complementary) "compatriots", "-17-A, -17-C". ~speciatly with regard t© the presence or absence Qf pyroxene in each, vis-a-vis magnetite. Also as regards the green micaceous mineral(s)/materials(s), etc: TM-04-8-9-4- 1 7-C: A hand specimen.. "Banded": with bands of "skarn" (pyroxene, +/-} and of "ore" (magnetite-bornite- +/-?}. One surface of this specimen is "slickensided ; with a "skin" of dark-green-black "smeared-out" mafic material(s); perhaps chlorite, +/-, etc, 23-A GMC DATA REPORT 3 4 8 . Page .103/127... Magnetite occurs as eu-subhedral.` crystals to anhedral masses, often in association .with "green micaceous" mineral(s)/material(s), intergrown with .lesser bornite, as well as, occasionally, trace .amounts of chaicopyrite (auks-anhedral).. The anhedral-subhedral- euhedral developments of each of these sulphide minerals varies from place-to-place. within this specimen. The "skarn" bands -- at ..least some -- .appear to actually. be "crushed zones/shear zones/seams" made up of very-#ine-grained magnetite and "crushedlrecrystallized" light "green micaceous" (viz. phlogopite?, .talc?/serpentine?/chlorite?) .material(s). [[Cf. descriptions of specimens TM-04-6-9-4-17-A, -B. Which, in light of the foregoing,., may merit/require. some "reinterpretation"(?).]] Note occasional patches/pods.. of very-well-developed euhedra of magnetite (the "prismatic magnetite" of SMA?), "micas", and fairly-well-developed crystals of bornite, chatcopyrite: Affording.an almost."pegmatitic" aspect, a "vuglike" appearance. One small-pod has eu- subhedral chalcopyrite surrounded by subhedral,. +/-, bornite, with magnetite eu-subhedra surrounding bornite and chalcopyrite. The adjacent. "green micaceous" is very-fine-grained (perhaps pulverized/ recrystallized?}, as part of apparent movement/structural deformation in this portion of the specimen {throughout the specimen, likely, with recrystallization of euhedral/+/_ magnetite and sulphides post(?) thESe effects ort previously-existing. "green micaceous" (or, rather, pre-existing pyroxene/forsterite/+/- [?]): A trace amount of - carbonate/calcite(?) is associated with this (and others) "pod". Note some occurrences of chalcopyrite (as weH as magnetite, .bornite) interleaved/ intergrown .with coarse-grained "green micaceousry material(s). [Where is the valleriite~~~ Why not here? Perh~s because no clinohumite??~ Where chalcopyrite occurs, the paragenesis consistently. is: chaicopyrite, then bornite, then magnetite. Bornite occurring within magnetite sometimes displays a rounded outline (due to the bornite having been partially "resorbed"?). Note some copper "staining" (tight blue green, ie.}, -here and there, on weathered surfaces of this specimen.. Perhaps also some blue (covellite?, chalcosite?, -~!-?) on some bornite crystal massesf surfaces (and. also on the rims of soma bornite crystals observed on "fresherp specimen surfaces}. Some "turquoise"-!green-blue- colored material(s) occurs in association with "green micaceous" materials} in a few places (weathering?/or?). When. viewed "end-on", quite a bit of the: "green micaceous" material(s) has this appearance,. even in perhaps "fresher" views afforded on fractured surfaces. -Here and there, ata~c/serpentine after/around "green micaceous" crystals refatianship does seem apparent/manifest. See; some .good examples of the "transition" between very-coarse-grained well-developed crystals of "green micaceous" material(s) and adjacent finer-grained materials. Generally .appears to be "gradational", hence perhaps supportive{?} of the "structural deformation/ disiocatian" premise/postulate for Yhis state of affairs within this specimen (as well as in the "compatriot" specimens "-~7-A, -t7-B"). Patches of buff-tight. brown eu-anhedral carbonate minerals} occur here and there, more ..often associated with coarse-grained "zones"/areas of the specimen: Note a .fair amount of `apparent evidence (viz. contortion of "mica" plates/crystals; "smearing"!shearing?, etc.; perhaps. also the coarse-grained podsJpatches/zones as subsequent recrystaliization effects?), supportive of this deformation/metamorphism(?). Much (but not all) of the carbonate material{s) mentioned above appears to occur onlwithin one .particular "shear surface/zone" within. the specimen. Some magnetite occurs as masses of perhaps "spheroidal" aspect (or is this. appearance actually due, rather, to the "conchoidaln fracture aspect of this magnetite?), with seemingly "radial prismatic" textures on broken surfaces {ie, of "spheroidal" grains /pods! 24-A GMC DATA REPORT 3 4 8 - Page io4/12z "whatever"[?~?]). Note these especially in association with coarse-grained "green .micaceous" crystals. Difficult to recognize possible: "valleriite": in this specimen, due to the weathering. effects. This specimen `is important in terms of many asoects of all three "-17-" s ecimenS Especially sa with regard to the Bugg ere t~QStl,tated "structural /deformation m~tamor hie" a r~ects of the coarse-grained < jfine-grained "green micacen~es" materials} as well as the presence/absence of "relict" ovroxene and -the paragenesis of the s,~-Lphtde minerals and m gnetite Each of th a threesspecimens affords unique manifestations- and should be considered in complementary fashion in any subsequent work TM-04-6-9-5-.... _ TM-04-6-9-~-1: _ _ An originally large specimen, subsequently broken into "many" pieces. Periclase (brucite} marble. Two variants present in #his .specimen. Une a lighter/whitish,' somewhat. coarser- grained rock, the other a greyer, denser (?), .finer-grained lithology. A'rather subtle, but ` apparent,~sharpish" border/contact. separates the two: A veinlfracture zone(?)1? is subparallel to, the latter, and trends along into the "border° between the two variants. This "border" likely(?} a sedimentary "contact", ie. "bedding plane". The nature of the periclase and the brucite, as welt as their genetic and textural relationships (brucite pseudomorphously replacing periclase), are well-displayed, .both throughout the specimen, as well as on weathered surfaces. The predominant rock-forming minerals, calcite and periclase {brucite), occur in a crystalline mosaic of typical "marble" texture. Minor/trace amounts of greenish-greyish-brownish fine-grained rr~aterial(s) disseminated throughout likely. are spinet(+/-?)..Some similarly dissemtnated very-fine- grained.black materials} may be graphite(?), and/or magnetite(??). A trace amount of quartz,. some appprentty as sub-euhedral grains, .occurs similarly. disseminated. TM-0~-6-9-5-2: A "salt-and-pepper", "dioritic-looking" specimen. Featuring pyroxene, plagioclase, quartz(?), .carbonate(?) matertat(sj, with lesser proportions of magnetite(?), pyrite,. ehalcopyrite(?), and associated. epidote{?) veinlets. Amphibole [tremoiite/actinolite (?)], serpentine{?), chlorite(?), +/-?„ are .observed in association with pyroxene, presumably as alteration phases. The pyroxene tends to Decor as stubby,. sub-euhdral, prismatic crystals, exhibiting good cleavage, a(orig .with associated alteration minerals.. The latter manifest themsetves as rims, sheaths, ..coatings, etc., comprised, variously, of amphibole(tremolitic/actinoFitic), chlorite, serpentine{?}, talc(?), +/-?,..adjacent to ,quartz+I-carbonate+!-epidote. -Fresh/unaltered pyroxene is black-very dark greenish in color: The: sulphides often occur as crystalline masses, aggregates, surrounding, engulfing, and/or .replacing pyroxene. Or as discrete. eu-subhedrai crystals adjacent to such. occurrences. Some fine examples of striated pyrite euhedra (including ,pyritohedra, cubes) `are noted, .associated with pyroxene, quartz(?), carbonate, +/-epidote, +/-?, Examples of chaicopyrite tetrahedra occur as well: At feast two sets of epidote/+!- veinlets are apparent, transacting portions of the specimen. Might this seemingly "dioritic" rock actually represent "endoskarn" material, in the .sense of APeksandrov (1998)? tt appears to .feature original "igneous" textural, mineralogical, and overall compositional characteristics, Perhaps a representative of "contaminated" magma, from a "carapace/shelf" of dioritic character.. Portions of which, presumably .were 25.-A GMC.DATAREPORT 3 4 8 Fage 105/12' - -- potential y available to intrude into portions of the adjacent/surroundeng country rocks as I eo o i I it m c c cu s n m v i a to ces a ha e d ctated/ ermitte f il' d/ ac mated. Providin m m i g 9 Y p 9 ag at c materials for. "apophyses" which might serve as metamorphic/metasomatic "facilitators" " " vis-a-vis es ciall pe y susceptible. country. rocks such as dolomites, resulting in formation of "skarns" and related materials. Per the concepts presented fy Aleksandrov (1998; and etc.}. TM-04='6-9-5-3: Specimen similar in aspect to TNI-04-6-9-5-1, which cf. White-colored;. a periclase (brucite) ,marble. Predominant rock-forming minerals occurring as a .crystalline mosaic of calcite and periclase (brucite}, .with associated minor/trace .amounts of spinet(?), graphite(??), +!-?, disseminated throughout the rock. The periclase (brucite) nature, and their geneticltextural relationships,. are rather nicely exemplified in this specimen._(Cf. specimens of similar nature,. from other nearby sample locations at the Arctic Chief.) As in other similar lithologies from this general area of the Arctic Chief, there is evidence of at least a moderate (strong?) degree of structural deformation having. affected these rocks. "Crushed/healed: zones", fractures, as well as some "slickenside°-like features,. occur, variously,. within these specimens, as especially manifested by the carbonate grains/crystals. Perhaps .not "pervasive", but "substantial". TM-04-fa-9-5-4: Specimen represents part of a "skarnn .zone. l:~nder the stereo-microscope, restricted to working at 30x/60x, and only on specimen surfaces (fresh as .well as weathered), this specimen is of the "challenging" sort. A "character sample", in the parlance. "skarn" material. Featuring pyroxene, +/-?. 1+Vith seams of fibrous "serpentine", +/-?, on/along .the .fractures. Specimen is "fraught" with slickehsides, epidote on .fractures, etc. Carbonate (calcite?) is abundant in parts of the specimen (ie. the "marbtefcalciphyre" iithologies, +!-). The.. specimen representing a "pyroxene +f-.:skarn --- forsteritelforsterite-rich zone --- calciphyre" sequence,. apparently.. Evidence overall of a "magnesian skarn" situation, in all likelihood. Note traces of sulphides. (pyrite, +/-?) in the "calciphyre" zone. Also, as well, in the "forsterite/forsterite-rich" zone,. near "seamsfshears" featuringtwith apparent "serpentine"(?} .occurring as prisr•natic/fibrous E:u-subhedra .oriented. sub-perpendicularly to "crush zone/fracture. walls" of forsterite(?), etc., adjacent thereto. Epidote present here and there as well. Similar "serpentine"/+!- occurs within fractures/zones which transect pyroxene. and/or other black .minerals in "calciphyre", along' with associated forsterite, +/-. Pyrite. occurs in trace amounts nearby, .sometimes as (fresh) cubes. Specimen represents a "retrograde" situationlset of assemblages ap arently Complex As such, not ins~nificant in the greater scheme of thus here. TM-04-6-9-5-5: .Specimen apparently presents a "diorite/endoskarn" to "garnet"(?} to "pyroxene" skarn contact(s). sequence [??]. Featuring a plagioclase-pyroxene- +/- "diorite" ("endoskarn"?), similar to TM-04-6- 9-5-2, etc. A thin. layer/zone of pinkish-light brownish garnet(?) [rather, zoisite?/clinozoisite?! epidote?/ .:......??j separates the "diorite" from ales-well-defined "skarn"(?} of darker and lighten minerals (viz. pyroxene?, carbonate?, +/-?) A trace amount. of sulphides (pyrite?, +/-?) occurs in this "skarn" zone. Cf. Aleksandrov (1998, & etc.). on "diorite", "endoskarn", "HHP granitoids", etc. 26-A GMC DATA REPORT 3 4 ~~: Page Zo6/i27 i '; TM-04-6-9-5-T3: A "banded" periclase (brucite) marble specimen. Predominantly consisting of white/lighter-colored bands (most of the' specimen) made up .predominantly of a crystalline .mosaic of the rock-forming minerals, calcite ..and periclase (brucite). , With .some: light. grey, much thinner, bands/zoneslhorizons of more-coarsely-crystalline calcite, featuring evidence of deformation of crystals (ie. representing a "crushed// healed/ recrystallized" zone within a formerlyloriginally more "homogeneous"(?) .marble/carbonate rock protolith(?). - Trace amounts of black/dark ("micaceous/mica-like"; ie. perhaps graphite?) mineral(s)/material(s) occur disseminated throughout, especially (more .prominently?) within the lighter" 'portions of the specimen.. Such "dark" material(s) somewhat/ appreciably less-abundant in this specimen than is the case in otherwise quite similar rocks from nearby sampling sites at the Arctic Chief. Perhaps the "two types" of marble in this specimen represent different "degrees" of metamorphismlmetasomatism, or differing degrees of "susceptibility" thereto; andfar "locally" differing degrees of structural deformation having. occurred -- for various reasons. -- within this specimen; and/or actually a case of two originally .different lithologies/ proportions of :constituents/components(?). Viz. "dolostone" vs. "marble" (??), Etc.......... (?). And/or merely a case of original "sedimentary" bedding??. TM-04-6-t0-4.. TM-04-6-10-4-A-1: Part of a "foot" (ie. appreciably Parger than a "hand") specimen ("-4-A-"), subsequently broken with a hammer into several smal6er (`-A-lal....:...") pieces/sub- speciinens. This one a ,dark. rock, with a vein(s) with attitude(s) subparallel to a dominant direction/ orientation of breakage of the specimen. Vein "fresh" <--> "weathered/altered", laterally, on broken specimen surface. Specimen is/seems relatively "dense", "heavy". A dark rock. Made up of pyroxene sub-euhedrz~, blackldark green, with alteration to tremo{itic/actinalitic amphibole. marginally (+/-talc?, chlorite?, ??}. Same manifestatians (warping, bending, of crystals) of deformational stresses having -been experienced within the rock. A minor {+/-} amount of clear-whitish la ioclase ? occurs in r p g O to granular to the redominan t a tered oxene. This la ioclase h p ( ) pyr p g sows c eavage, and .occasional subhedral ',, crystal forms/outlines, with .darker/smoky-brownish central cores (perhaps at least in part quartz?), and clear-whitish grain margins. (Cf. other specimens in the "TM-04-6-10-1 <- ` -> 6" series). The latter. presumably representing igneous zoning, though some sort of ~, „ secondary/overgrowth henomenon mi ht also be invoked here viz. wi P 9 th uartz erne ( t q 9 , +/-? ).. Nate occurrences of vein(s) of quartz(?), ±/- calcite/carbonate, +/- epidote, with -vague to moderately-well-defined margins, adjacent to .the "pyroxene" +/- rock. Iron-stained, as well as with traces of ,malachite, near a smelt "pod" of probable chalcopyrite(?} +/- magnetite, +f- ("green calcite?). Some offshoots here and there of "epidote", +/- "cryptocrystaliine" .quartz" (??}, into adjacent rock walls. The chalcopyrite crystals are eu-subhedral, "tarnished", and lie within the vein. There is evidence of shear parallel to thee. plane of the .vein, with "unconformity" .surfaces vrithin the vein.. Evidence of "altered"/ "silicified", +/- "carbonatized"(?)/"epidotized"(`??) relict (euhedral, +/-) pyroxene grains within the vein. Two °generations" of carbonates, a darker brown ("earlier"?), 27-A GMC DATA REPORT 3 4 8 Page 10/127 .and a clear whitish (°later"?), in the veins (?'?). [And/or magnetite(?}, +/-?, with carbonate, quartz(?). Or quartz brownish}?; then carbonate?]. Original pyroxene grains eu-subhedra!, .oriented variously ("randomly"?), with (quite) subordinate plagioclase, +/-? (including carbonate)..Wtagnetite sub-euhedra disseminated amongst the. pyroxene grains. Epidote, quartz, (chalcopyrite?}, carbonate, (chalcopyrite?), the apparent(???) depositional sequence in veins,. from margins; inward. Pseudomorphs of carbonate?/quartz?/epidote?/+l-? after pyroxene, with retention of relict crystal .outlines, ` cleavage noted(??)_ Weathered specimen surtaces suggest "plagioclase", magnetite, +/-quartz, epidote, carbonate, pyroxene do in fact comprise portions. of this specimen, per the above/foregoing "treatise"/"exposition". A sample of "pyroxene skarn"(?}, rather. than "igneous", _ie. ?? TM-04-6-10-4-A-2: Another, larger, broken piece of "-4-R-.....". The- "other half", actually of a piece broken from "-4-A-1..:." originally. "Same as its mate". TM-04-6-10-4-A-3c A larger broken piece. Observe sub-euhedra! outlines of "pyroxene"(?) crystals (12 mm, +/-, and srnalier) here and there; "veinlseam" of carbonate(?), +!-. The large "pyroxene" grains. show. 87/93-degree cleavages (?), are black-dark green, could be altered to .hornblende{??), and .then to tremoliticlactinolitic amphibole, marginally (+/-talc?/+/-?). The. eu-subhedra abut one another at various (--> 90 degrees) angles. ("glomeroporphyritic"/"blasto-"), originally???). Sample is "seamed°, with epidote, quartz(?), carbonate, +/- "opaques" (???}, TM-04-6-10-4-A-4: Largest broken piece. Calcite euhedra in one Ic~cation associated with a vein". "Color index" of this sample = 60+ (to "++"). Calcite {cleavage remnants). =16 mm, +/-. "Much" of the "late"-clear-whitish material in the specimen probably is calcite(?). 'Though some is likely plagioclase (?), +/-?, "Seam/vein" is quartz -and calcite, +/- .epidote, +/- . Perhaps (?) most likely (??) an "altered/retrograded" ."endoskarn"?? pyroxene .and plagioclase rock ("exoskarn"?), with magnetite; veined/seamed .with calcite+/-quartz+/- epidote+!-magnetite(??~+/_?. Possibly (?) trace of very-fine-grained "opaques"; viz. "sulphides" (andlor "graphite" ?I /+/-/or "disrupted" magnetite (??), disseminated throughout the specimen (??). TM-04-6-10-4-B-1: Once part of an original "foot" specimen, now broken into several pieces. These. labelled "TA4-04-6-10-4-B-1, -2, -3". .Note euhedra! (well-developed) prismatic pyroxene (clinopyroxene?} °ghosts" on a (freshly-broken) fractured .surface, which also confains sulphides. The "ghosts" now pseudomorphed --> hornblende(?} +/-?. Carbonate euhedra (and also .some less-well- deveioped), on the opposite (also freshly-broken} specimen surface (pinkish-buff-whitish}, with sulphides present as weiL Note similar "ghost" features in other. "dioritie" rocks in this general area. Are these. originally igneous in origin, or metamorphic/metasomatic? Scattered eu-subhedra (and less-well-developed) of sulphides ("molybdenite"~ galena magnetite??) on specimen surfaces .Specimen broke readily along these. surfaces, thus they .are "zones of weakness", +/- "zone(s)" of structural significance within this,. as :welt as the original larger, specimen. Featuring mineralization/aiteration associated with them. 28-A GMC DATA REPORT ~ 4 8 Page lOS/:127 Apparently featuring euhedral. crystals/platelets of molybdenite(? -- hexagonal seemingly opaque, shiny. moderately "loosely-leaved". Or alternatively (~?) some sort of peculiarly. "blackish/bluish", shiny to "dull-appearing" black mica (viz. biotite ~hlogopite j??~; or graphite(?~) Or "smeared" galena +/-? A penknife point succeeded in "peeling" a curling "shaving" of a .layer from one or these hexagonal crystals ie "looks metallic"(~ Host rock/specimen overall: Features eu-subhedral pyroxene(?) --> "amphibole" initially hornblende, then subsequently --> tremolitic/actinolitic .variety. Plagioclase is another .principal .mineral present in this specimen, occurring as eu-sub-anhedral clear- ,whitish .grains. Minor. euhedral and fees-well developed quartz(?) is also present.. Thus the rock might be considered to be aquartz-bearing/quartz diorite,. with an "igneous-like"{?) texture. of intergrown crystals. Evidence. of a moderate(?) degree of structural deformation throughout the specimen, with some. "veinlets° along semi-planar. "shear/fracture" surfaces, which often feature very- fine-grained carbonate (calcite?} +/- quartz(?), +/-?. Molybdenite/? is essentially restricted, as far as can be discerned in this hand specimen, to one zone/fracture/shear (??). .Relative proportions of pyroxene/etc. vs. plagioclase seem. to :vary within the specimen ("banding"?)..Thee larger-scale "ghosts" mentioned above ,are .not readily evident as such. at 30x magnification, likely slue to the replacing/pseudomorphing materials ("amphiboles", /-) "masking/confusing/obfuscating aspects of the original pyroxene crystals.. Trace amounts of epidote occur here and there es ecialfy in the "zone" which features the apparent molybdenite(?). These "molybdenite" euhedra are hal#-again or so as large as adjacent ~gyroxene~" --> "amphiboles" +/- grains The "molybdenite" grains measure on the order of 3 0 mm in "width" of hexagonal plates The "other/whiter" side of thin specimen features similar "molybdenite" more-widely spaced/spread across the hammer-broken fracture surface and they are of similar ie. 3 0 mrn. and smaller) "width" as their counterparts on the other °darker" surface of the specimen. A penknife point drawn across a surface of one. of these "platelets° readily leaves. a groove (?). Though: this material seems uncommonly "well-crystallized" for "graphite". Thou h in reflected oblique illumination at 30x magnification it also looks perhaps a "bit -too black" for molybdenite{~~) These "enigma ic' opa~ues are intergrown/occur with "pyroxene" --> _ "amphiboles". +/-. and/or plagioclase. on this surface. Occasionally "interleaved" with "tremolitic/actinolitic a~hiboie"/+/-. ..:One massive accumulation of "mo{ybdenite" crystals seems to have "reacted: with/been altered to„ a pale yellow-buff "box-work/network" of prismatic/lathlike crystalline aspect (with voids). Sug, eg sting perhaps the "parent" m~uerial in ihis~nstance was not "graphite/carbon" but rather, "something else"/a ~ hp ide (viz molydenite~ and/or~~ le molybdenite/sulphide --> a sulfate carbonate +/- etc. (?). This occurrence lies within an area of plagioclase (+/- carbonate) and "~tyroxene" --> "amphibolesn +/- not far from a "zone"/"veinletH featuring rather well-crystallized epidote/+/-?. White-pink materials on this specimen. surface are. carbonate (calcite?), quartz, plagioclase, +/-?. The "ghosts" (1.2 mm and smaller) of "pyroxene" (?) euhedra mentioned above are apparently on the "darker" surface of this specimen. They are now comprised of a pseudornorphous assemblage of "amphiboles" (viz. hornblende, followed by "tremolitic/actinolitic" material). For the most part, these occur as fine prismatic crystals, more or less oriented in keeping .with than of the "original" pyroxene crystals. There are, however,. orientations at odds wRh this. This latter effect may be more apparent than real, 29-A 6MC DATA REPORT 3 4 .$: Page l09/127. however, since the "original" pyroxene(?) crystals occur in various orientations (even presently, within the "ghosts" -- ie. the "ghosts" perhaps not igneous in .origin, but,. rather "--blastic", due to "other-than-igneous" -- ie. metamorphicfinetasomatic -- circumstances.. "Growthfreplacement" (???). In places, such as shown on this surfacelportion of the overall "-4-B-...." sample as a whole, the mineralogy, +/- the texture, appear to be more a "gabbroic"?f"skarnoid" type of ` affair (?!?). The "original" pyroxene(?} crystals (black, shiny) are often. seen as representing "books"/".patches" of "platelets" -- ie. , "mica-like"(?) -- (biotite/phlogopitef???). This .appearance might(??) be the. result of "alteration", andfor "breaking" with hammer, of traces of pyroxene cleavages on pyroxene "prism" faces (???). Cleavages, "ghost" morphology/outlines are, however, apparently.. indeed "pyroxene-like" (?).:.The "ghost" outlines are. only apparent withoQ~t magnification, and are not readily. discerned at 30x. It might be conceived that the rock originally was more akin to a "pyroxenitelgabbro" ("meladlorite"?) than a "diorite"; perhaps even more likely (?) a "pyroxene skarn", retrograded, fractured, mineralized, etc. (?). It does in fact seem that the apparent "mol~b~lenite" is most likely -- though reauirina further confirmation -- just that. Per its metall~~ ~~o~rAr and other characteristics. its color its observed apparent "boxwork/network" alteration and other attributes Although "smeared-out" occurrences of sulphides such as Helena etc remain possibilities yet to be dismissed While "graphite" seems perhaps the least (ikety candidate. A!I in-all a most interesting specimen. If perhaps remaini~ a bit. "enigmatic", at the preliminary level of "triacte/analysis" performed here petrographic scope time.......lll TM-04-6-10-4-B-2, This sample ("-2") - is from another {opposite) end. of the larger specimen ("-4-B-.....") from the previously-discussed "TM-04-6-10-4-8-1" sample (which cf.). Sample "-2" shows two rather distinct (in mecfa-appearance) apparent Ilthogies, one dark grey-black, with a color index of about 50+; the other 'one a lighter grey-green,. thQUgh also. with a color index of about 50+, if the "green" material{s) isfare considered "mafic". A moderately "sharp" border separates these two: (Vote some "ghosts/mega-crystals-blasts-phenocrysts" (?), on the order of 1.2 cm and smaller. These. appear to be somewhat akin to siimifar features observed in sample "-1": However those, in the present sample have perhaps(?)amore "hornblende-like" .aspect (?) than the apparent "pyroxene"{?) analogs !n "-1" There is actually a vague. indication of "bandingflayeringn, with bands" of "black" versus "grey-green" alternating. Each band on the order of 1 to 3 cm in apparent thickness, as viewed on the specimen surface. Two major broken. specimen .surfaces,. one "fresh" ("F°), the other .weathered (°W"). "F Presents some fine examples of euhedra! pyroxene (with .the distinctive cleavages), surrounded by rims of tremoHticfactinolitic amphibole, +f-, within/adjacent to sub- euhedral clear-whitish plagioclase. Some of the plagioclase !s altered, variously, to (apparently) epidote, +f-, in places.. A "banded/iayered° specimen, with darker ("pyroxene-rich") versus lighter-greenish- (plagioclase+/-epidote, +f-? - richer) "zones/bands". A few thin .planar "seamsfveinlets" transect the specimen, with associated "more intense" 30-A GMC DATA REPORT 3 4 8 Page lio/12~ development of epidote/epidotization of adjacent plagioclase, as well as some concentrations of _ FeO/OH (now, of present) material(s). Trace amounts of "magnetite"(?)/+/-"limonite" are scattered throughout the .specimen as well. A ' "plagioclase +pyroxene (now --> "amphibolesA, +/-?} rock". °Diorite, meta-diorite, gabbro, etc. (?). "Igneous"? Ora "pyroxene-plagioclase: "skarn/skarnoid"?? "W": Suggestions (viz.. cavities, "drusy surtace"} of carbonate on weathered surface of specimen. Trace of "molybdenite"(~/"praghite"(.~~}J"smeared-out" sulphides. +/- ? !/ AND/ OR ~ on surface This surtace is the extremE~p~site end of the specimen from the ~ecimen TM-04-6-10-4-8-1 (which cf.l. This moderately} weathered surface features much "whiten -- though with apparent "iron-staininca" - material (°crust~~ and/or "fracture surfacefseam/veinlet"~l The "molybdenite°(?) occurs here and there, associated with white material(s) ie. plagioclase +I- quartz(?) +l- carbonate? +/-?). as eu-subhedra, similar to that noted on the "-4-8-1 n specimen. The "molybdenite"(?) is fresh unweathered (~• perhaps rather ~r~phite" thus~~l. Traces of eu-subhedral "rutty" seemi Ol~-aaue (magnetite?- sul~hide[si~} grains acr.-,r on this surface of the specimen. Some pyroxene crystals show slighUincipient weathering (?) --> "rusty° material(s). Note. another "ghost" pyroxene, about 1.5 cm in maximum observed dimension, with euhedral crystal outlinelshape, .weathering/altering -->?. NNote/Aside]--- Re/ "diorites" etc. Esp. in the Whitehorse Copper Belt. +I-. "Igneous" diorites? Vs. "pyroxene-plagioclase" rocks; esp.- as per Aleksandr6v {1998, & other papers) ?Criteria for .distinction? Endaskarns....... Exoskarns....... Skarnoids.......... Contamination.:...... Reaction......... Assimilation......... Melting......... (esp. "of countrylhost rocks"; 'and/or "skarn"....:... ) "Meta-diorites"........... "Gabbroic rocks" -- compositionally (mineralogy, chemistry); texturally; .modes/loci of occurence; etc. (?) "Meta", "Meta'd°, "Meta", - "diorites". "Granitics".:....... "Super-heat".......... "High-heat-producing" (HHP) "granite/granitic" magmas/melts........ (Cf. Aleksandrov, esp. his. " Wit. Austell"/HHP paper, and his1998 book). TM-04-6-10-4-B-3: Similar to "TM-04-6-10-4-B-1". of which the present. specimen, "-3", is the larger "parent" portion, broken in turn from the largest (in "reserve") "foot" specimen ("-4-B- ......."}. While. (as !mentioned to Jim Coyne) an even- larger, "penultimate", parent resides(ed) along tike "Mt. Mc{ntyre"{?} ,road {on the. "southish" side of ,the road), about 0.3 miles uphill from. the junction of thin road with t:he "road/two-track" to the top of the Arctic Chief (west) pit north rim. (cf. field notes). The present specimen ("B-3")-features on the order of 3-5% "molybdenite" (,)/"araQhite"~w)!"smeared" other material(s) viz, galena. other sulphides. etc. (??). located on the "fresh" fracture surface {"F°) of the specimen which surface is the "mate" to that/the similar one on specimen "-1" (which cf.). This surface( F n his intersected/transected by a number of moderately-spaced #ractures culling across it at high (---> 90 degrees) angles.. These latter fractures. are not obviously. "mineralized". More akin to "cleavage" in aspect (?); "laten, hence, presumably. The opposite side of the specimen ("W") is moderately. weathered, with appreciable whitish 31-A GMC DATA REPORT 3 4 8 Page 111/127 +/- "rusty" material(s), as well as slightly-moderately weathered pyroxene, +/-. These two surfaces "W" and "F", are subparalfel, with several.. variously.-we11-developed "seams/veinlets/fractures" ..subparalfel to them, within the specimen. Also note several:. "veinlets", with associated "whitish" material(s), trending at high. angles to both. the "W" and "t=" and the "cleavage-like" trendsffractures. In essence, more or less a "three- dimensional" network. A "cross .section" of a "weathering profile" at the larger butt end of the. specimen has much to offer in terms of elucidation of mineralogies and .textures of this .specimen. The °cleavage-like" fractures .may .have at least some associated quartz- (ie. silicified"}, +/- traces of iron-bearing material(s).' The "mol~bdenite"~} crystals/platelets seem to have a "coherency" as individual sub- platy flakes suggestive of a "metallic" rather than "graphitic/carbonaceous". character (?l. Though as well there may well be some smaller disseminated) grains/raiatelets/etc of graphite/carbonaceous material present on this fracture surface !??l: Same of the"mol~bdenite" (?) crystals/platelets are on the order of 4.0 mm (+/-) in maximum dimension of the hexagonal surfaces The white/whitish (sometimes slightly "rushy/ferruginous"?) materialO associated with these "molybdenite" (~) grains may be plagioclase/auart~al/carbonate(?1/+/ ? Egidote is not uncommon in roximity as well Also some cp~ger-bearing sulphides (viz. chaL_ co~yrite +/ bornite. +i-?) occur s r is I~ on this fracture surface (associated with carbonate quartza +/-?} Some green ..(malachite +/-material(s) associated as. presumab~ alteration andlor weathering products These sulphides are eu-subhedral, as wf~ll as less-well-developed Seen best on one "edge of-the specimen near the "wedge-end" of the specimen. Some very-weN-developed "tetragonal-IikeA euhedra noted here. Some "mo(Xbdenite"(?) is associated with/intergrown with "tremolitic-actinolitic" amphibole +/- and relict pyroxene. There is a "chlorite-like green" cast to .some of the "whitish-clear" mineral(_s) (viz. auartz~ carbonates plagioclase?/+/-?} akin to an "internal dustir~" of inclusions of "extremely fine-grained" green material(s) [??]. "Cooper--"???. "W,,. Surface. is moderately weathered. Evidence of .weathering of mafics (pyroxene; --> "tremolitic/acinolitic" .amphibole, +f- :...., with "drusy" very-fins-grained crystals of .bright --"epidote"-- green eu-subhedra, seen on relict pyroxene crystals, etc: ---> surficial crust, on weathered surface of specimen; more or less "ubiquitous"). Also weathering of carbonate, +/- plagioclase, is evident.- Numerous holes, cavities are noted, though there seems to be no (other compelling evidence of "weathered-out" sulphides, or magnetite (?). All in all an interesting specimen Especially with regard to the chalcopyrite +/-bornite + malachite + "mo[kbdenite"(~ associated on the "F" surface. TM-04-6-10-5; "Dioritic" ' (?) rock.. Sulphides. and trace malachite. on a "readily broken" (with a hamtn ~ surface fracture"?~ Blebs/blobs/patches of black materialtsl associated with these sulphides. - Specimen has a "granitic" aspect, overall, with vague "bandingflayering" in places. A "salt rand pepper" texture,: megascopically. "Rusty" weathered surfaces staining near sulphides Chalcopyrite -with associated white lcarbonate~~, red-brown (hematite?. garnet??l r~llow-green a idote?). clear-vitreous 32-A 6MC DATA REPORT 3 4 8 Page 112/ l v ((auartz~~/carbonates?/feldspar~~ material(s.) Cha(capyrite is eu-subhedr al, with occasional weatheredt?~/altered(~l associated malachite hematite(/merc ury-bearin minera~slf???~, This chalco~yrite +/- assemblage is essentiallX restricted to a planar zone of .relatively small thickness with evidence of structural movement within this zone (slickensided features alteration) Essentially chalcopkrite~ +/- ovrite(?.) some bornite ~~ perhaps -- -> hematites +/- malachite etc. ?. at least in ap rt ?). Note .other "veinlets" of epidote(?), quartz(?), feldspar(?), +/-?, which transect this zone, here and there. Some such feature apparent. very-fine-grained. carbonate(?) of pinkish hue. Black hornbtendic(?) amphibole, similar to Ghat found less-intensely altered in the surrounding "country rock" of this specimen, is, in this zone, moderately/strongly altered, peripheralry and along cleavages, to a light green prismatic "tremolitic/actinotitic" amphibole, +/-?. The "host rock/diorite/endoskarn/exoskarn"(?) 9S made up principally of clear white plagioclase (?), and dark green to black amphibole (note cleavages)/+l- "pyroxene". The latter "mafic(s)° show(s) various .degrees of "alteration" ---> °tremolitic/actinotitic" amphibole, but, for. the most part, less .intensely so than is the case within the sulphide- bearing zone.. Eu-subhedral magnetite is an important third constituent mineral in this rock. Plagioclase, pyroxene(??)/amphibole. (hornblende?, +%-?), are. eu-subhedral, intergrown in an apparent (?) "igneous° texture ("granitoid/dioritic"), of medium-fine grain size, mare or less equigranular constituent phases. Some epidote alteration of/marginal to/within plagioclase, .and/or "amphibole(s)". Also +/- some °flakes/specks" of magnetite(?)/ galena(??)/molybdenite(???)/graphite(????) on "dioritic° rock. proximal to the sulphide-bearing "zone". Some lozenge-shaped amber eu-subhedra within the rock might be sphene (?)/+/-?, in trace amount. °Country rock° of °dioritic° aspect/flavour, mineralogically and texturally (?). [[However --- "genesis" is another matter. Especially given/in the context Df the (Deal-areal-regional geological setting/environment.]] Perhaps/likely (?) an example here of the not unusual °dioritic° border/ margin/ carapace/shell associated with "graniticn intrusive suites. in many places .elsewhere. Apparent examples of such too numerous to do more than aPlude to here, in this report.. Cf. also Aleksandrov, .1998, and other publications; especially his °HHP° paper at the St:"Austell. conclave. Implications for the,. Arctic Chief? For the Whitehorse arealCDpper Belt? Regionally? Cf. also Moorhouse, .1959, .regarding diorite, .especially page 244 regarding hornblende after pyroxene morphology, etc.; also pp. 256-3a1. "A lot. of Tore", in Moorhduse (Hogarth, pers. comm.). ,4t a location on one edge%orner of this specimen note one very-we1i-develo ep d eight-sided in part euhedraf crystal (Qyroxene originally) Replaced ~y epidote. in the center and b~ "malachite° at the crystal margin with some relict "pyroxene" remaining. in the central :core. Further; as regards the nature of the dark/bla.ck "blebs/blobs/patches" seen. megascopically on the surface. of the specimen; near the. sulphides. "Megasopically" they have a "blastD"-crystalline aspect, with seemingly a "metamorphic" equivalent of "poikilitic" texture lie. "poikifoblastic"). Viz. the amphibole?/hornblende??tor'....'....... ?, with "inclusions" of "plagioclase", "pyroxene", +/-?. They seem to be, rather, "composites" of .variously-oriented eu-subhedral pyroxene; which has .been moderately "altered --> utremolitic/actinotitic° amphibole, (+/-). 33-A AMC DATAREPORT 3 4 8 Page 11`3/127 Seemingly via an intermediate °hornbiende° step/stage. The pyroxene. having a decidedly "black, shiny; hornbiende-like appearance to it. Ie. (?) :pyroxene --> "hornblendic amphibole" ---> "tremolitic/actinolitic° amphibole, +/-. Was the hornbiende originally of igneous ("dioriticn?) parentage, initially? Subsequently..: pseudomorphed to pyroxene, via change (increase?) of temperature, and/ar other effects related to changing pressure; composition conditions? With subsequent "retrograding/alteration resulting in formation of tremoliticlactinolitic amphibole, +/-? Some of the outlines of the "mega" crystals abut chaico~yrite +/- g_arnet~ +/-? as though .they crystallized "side-by-side" (??). Or rather sulphides "quartz"~, epidote carbonate +/- "re~lacive" of "pyroxene"~ +/- (?)- [[Like.... (?7111 TM-Q4-6-10-6-1: An outcrop specimen. A "salt and pepper" rock. "Dioritic"(?). T'wo variants noted in the specimen. The "contact/border" between them is relatively .distinct/sharp. One is 'a fine-grained equigranular rock, featuring apparent "pyroxene" (eta-subhedral) and plagioclase. "pyroxene" features rims/borders of apparent "tremolitic/actinolitic" amphibole composition. These "pyroxene" grains occur intergrown with sub-anhedral plagioclase, +/- quartz(?), +/-?. Color index = 40+; ie. "diorite/meladiarite" (?). Trace of molybdenite(?t/coca hite(~~)/magnetite(~)_ Mol'rbdenite~/"smeared" galena or other suiphides~f"giant" ma~netite~ occur( associated with carbonate. at/near the margin/contact/boundar~r between the fine-grained and meditam-grained variants of this specimen. Likely (?) magnetite, but might be "mica", viz.. biotite, phlogopite (?). Persistent along this "contact", in trace amounts. Apparent magnetite. euhedra noted. Note also some oxidation products ("rusty", +/- 4mm in size) associated with this "contact" zone (and elsewhere, too), where the fresh and weathered surtaces of the specimen meet. This material(s). persist(s) throughout the "medium-grainedp portion of .the specimen. The other variant is amedum-grained rock,with (ergs black eu-subhedral crystals of "pyroxene"(?), within lighter (plagioclase?) material(s). One (the. largest noted) euhedral prismatic "pyroxene' crystal is 14 mm in maximum observed dimension; others are in the range of 7 mm and smaller. The weathered surface of this medium-grained rock shows the major mtnera! constituents °in a different light", as it were. Consisting of apparent quartz, plagioclase, carbonate, pyroxene (with "amphiboles"), -magnetite, green euhedra of spinet(?)/??, and ~~erha~s(~l some moiybdenite(~) Some eu- subhedral clear amber crystals (spinet?/+/-??) occur in this :rock type, associated with pyroxene, .plagioclase, +/- quartz. Trace of .garnet (??) .noted, as very-fine-grained, red- amber, eu-subhedra, +/-, associated with pyroxene. Might the pyroxene "euhedra" originaity been "giomero-porphyritic/-phenocrystic" groups. of .crystals, now "altered"/whatever. --> "uratite" (viz. hornblende? --> tremolitic/actinolitic amphibole%+/-epidote{+/-phiogopite or biotite in places? The "mega- euhdrat" outlines now consist of a mass of variously-oriented eu-subhedral .relict "pyroxene" crystals --> "amphibole(s)" --> +/-. Similar, to .relationships observed in diorite-like" specimens from- TM-04-6-10-4, & -5 (which cf.). Two kinds/generations of plagioclase noted. An "earlier", often eu-subhedral, clear but brownish" variety. This surrounded by a more abundant uwhitishn variety (?). [The _ "brownish" could(?) actually be "later" than the "whitish" (???).] The "brownish" ranges from euhedral <-,> "rounded". Perhaps these relationships, actuallylmerety representing a 34-A GMC DATA REPORT 3 4 8.. Page 1I4/127 " " " " matter of zornng rn plagioclase (?),..from dusty/smoky lettered cores --> whitish rims. (??). Likely... (?), or so it appears, in some views. le. "zoned" p{agioclase. ]Perhaps "likely so' ; but not "assuredly so". As is the case in most matters geologic -- and. otherwise. Cf. Smith; .Spry, etc.] Does this suggest/indicate(establish/demonstrate/"prove" the "igneous" nature of ..this plagioclase? .........+/-the rock? At least during the- crystal){zation of the plagioclase adjacent tofaround the "pyroxene" eu-subhedra, etc. (?}. le. crystallization from a melt, "contaminated" or otherwise (?). With attendantlpresumed implications as to "dldeltaT", "HHP"; etc., per Aleksandrov (1998, and other publications;. especially his "St. Austell" paper).. fe. not a "plagioclase-pyroxene rock" as a metamorphiclmetasomatic product. But, rather, aportion/variant. (perhaps/likely "contaminated") of the 1a "main magma" body (?)• [Asidelquestion: can/does a "contaminated", perhaps/likely(?) less-basic,. melt crystallize medium-fine-grained. eu-subhedrat pyroxene, plagioclase,. +/-, at' lower temperatures than the experimentally-"demonstrated" :phase. relationships/mineral stabilities "regime" (at "thermodynamic equilibrium", ie. (??). Perhaps as a "non- equilibrium" °quench phase"1"over (or under) -shooting" sort of thing (??). "Reaction/assimilation" as a °type" of metamorphism? Cf. stabititieslassemblages per various PTG's.] One freshly broken surface on the specimen shows some minor iron-staining at an edge where the surtace adjoins one of the other, weathered, surfaces of the specimen.. TM-04-6-10-6-2: A hand. specimen now broken into- six pieces. "Float" sample. One fracture noted.. cutting this specimen. Vaguely-defined "planar" seams occur subparallel to this, or at +/- 45 degrees to it. Specimen displays a "salt and pepper" texture, megascopically. The lighter grains showing a "pinkish" cast, the darker ones agrey-green aspect. (Altered/metamorphosed- metasomatized?). Light .green material "diopsideA? An battered pyroxene", ---> "tremoli is/actinolitic" amphibole, +/-? Crystals displaying good outlines suggestive. of "pyroxene". Plow made up of crystalline material(s) with some apparent retict/vestigial "87-93 degrees" cleavages, but with overall color aspect of "diopside/tremolite-actinolite" (?). Some of these crystals are clearly eight-sided: in outline; prismatic forms are displayed as well "Pinkish" material(s) originallylstill(?) plagioclase (likely).. Pink representing alteration --> clinozoisite/zoisite/ENn-epidote/+/-?. Now a subtle "rose quartz" color,- in places (due to zoning,. or to thickness of viewed crystal, etc.?). Though at least some of this pink material might actually be carbonate; some might be quartz(?}. Traces of apparent zoning {?), with brownish cores -and. lighter rims. Could {?) be zoned garnet, .rather than plagioclase {?). Occasional scattered. crystafsfpatches of dark brown-black "graphite-tike-looking" rnaterial(s},..especially associated with "plagioclase", Traces of light. yellow-green epidote(?) °are similarly associated, as eu-subhedrat crystals. Also note some. amber-brownish eu- subhedra of spinet(?)Igarnet(??)/or?. Possibly (?) also some light- red-pinkish. garnet(?) here and there. Also (appreciable) eu-subhedrat magnetite (?)/?, as well as ph(ogopite(?)fgraphite(?)/sulphides, disseminated, here .and there. 35-A GMC-.DATA REPORT 3 4 8 Page 115/12 Note a few "prominent".internal fractures/shears, which intersect at various .angles, in a moderately-spaced "network". Some. "sl!ckensided" features also noted. in association .with these. Lithotogy(ies) now, a pyroxene ("altered" --> °amphibole(n, +{-) - plagioclase -garnet - magnetite (minor} -carbonate - +!- quartz? - +/-? "rock", .with .textural .variants. An "altered/retrograded/(ca!c)-skarned" roctc (?)..Which could: have had a "dioritic-gabbroic° proto!ith. At !east some of the "pinkish" material could be carbonate. There. are some masseslpods of magnetite(?), here- and there, as well as the disseminated eu-subhedra: Weathered specimen surfaces afford much useful informationlperspective regarding this specimen. The "light-green" material(s) .does seem to be (altered) "pyroxeneH (now diopside(?], and/or "tremoliticfact!nol!tic" amphibole(s), +/-), based on the nature of observed crystal shapes/outlines, and cleavages, especially when vievued on weathered (moderately+) specimen surfaces. The pinkish-whitish. euhedra appear to be feldspar, presumably .plagioclase, as similarly :viewed on wreathered specimen surfaces. Occasional bright green six-sided crystals are probably epidate. Also noted are variously rounded/weathered apparent euhedra! crystals ' of °magnetite". .Weathered specimen surfaces are irtformat!ve at 30x/60x viewing, especially with the stereomicroscope. TM-04-6-10-8-A: Hand specimen. "Oreg. Massive specimen of magnetite, with scattered patches of serpentine(?} jgreenish, to huffish-yellow on weathered surfaces]. Traces of copper-staining (light b(ue-green} on same fracture surfaces. TM-04-8-9-2-~: Garnet (reddish-brownish) and pyroxene (dark green/black) "skarn~, with crystalline calcite ..(orange-pink), +/-. (Cf. similar specimens TM-Tit-7-30-1 & -2.) "Typical skarn", sent to SMA January 2005. Cf. SMA comments: TM-04-10-12-.... -TM-04-10-12-22-A'-101 Massive chalcopyr!te, magnetite, +/- bornite; with associated pyroxene, calcite(?), quartz(?), malachite (featuring some nice acicular crystals); serpentine(?), +/-?. TM-04-10-12-22-A-102: Massive .magnetite-bornite-chalcopyrite; +/- calcite(?), serpentine(?), quartz(?}. TM-04-10-12-22-A-103: Green "mica" (phlogopite, presumably); magnetite,. bornite, pyroxene(?}; serpentine(?), .calcite; ...quartz(?), +/-?. TM-o4-10-12-2a-a-toy: - Massive magnetite, with coarser crystals of bornite(?) [with associated azurite/malachite 36-A 6MC DATA REPORT 3 4 8, Page.116/12~ on the weathered side of the specimen]. Also crystals of forsterite(?)f --> serpentine(?). Also some calcite(?) and/or quartz(?). A small specimen, but one with some interesting textural. relationships. TM-04-i 0-12-22-A-1 1 2: A "float" specimen .from the "-22-A" area. Note some subtle "banding" in mega-view. Periclase (brucite) marble. Predominant rock-forming calcite .and Periclase (brucite). Trace amounts of Mack opaque mineral(s): magnetite(?), ludwigite/vonsenite(??1 +/-?.-Also some spinet(?), forsterite(?): TM-04-1 0-1 2-22-A-1 1 3.: A carbonate rock specimen. "Fooat° from. the "••22-A" area. Features two types. of carbonate rocks, one white, the other grey. Both Periclase (brucite) marble,. lithologically. The Periclase-brucite relationships are especially evident on the weathered .specimen surface. Weathered surface also shows trace amounts of black opaque mineral(s),. and some sulphides (pyrite?land/or??. jAlso perhaps~~~ molvbdenite ?? . TM-04-1 0-1 2-22-A-1 20: Specimen from a LARGE chunk of ore material at locality "-22-A9. Comprised of magnetite-bornite-phlogopite- ,+/-?. Note varying grain. sizes of crystalline phlogopite. TM-04-1 0-•12-22-A-1 21 : Specimen from a LARGE "boulder°/chunk of ore material in the "-22° .locale.. On the "benchn/rim of the south side of, and above, the entrance cut at the Arctic Chief .(west): pii. Specimen consists of magnetite-phlogopite-bornite, +f-?. TM-04- 1 0-1 2-22-A-1,22: .Specimen .from. the same general locality as the "-22-A-121" sample, above. Consists of magnetite-bornite-chalcopyrite, with much. associated phlogopite as well. (+/-?). TM-04-i 0-12-22-A-1 23:. Specimen from the same general locality as the "-22-A-121" sample, above. Consists of pyroxene(?)-magnetite-bornite-chalcopyrite-phlogopite{?)- +/-?. TM-04-10-12-22-A-124: Specimen from the same general locality as the "-22-A-121" sample, above. Consists of pyroxene(?)-phlogopite-magnetite-bornite-chalcopyrite- +/-?. TM-04-1 0-1 2-22-A-1 25: Specimen. from the -same general locality as the "-22-A-121 n Sample, above. Consists of pyroxene{?)-phlogopite-magnetite-bornite-chalcopyrite- +/-?. T M-04- 1 0- 1 2-22-A-1 26: Specimen from- the same general locality as the "-22-A-121" ample, above. Specimen is "banded", with opaques .versus .non-opaques: magnetite-bornite-chalcopyrite; forsterite(?)- TM-04-10-12-22-A-127: _ Specimen from the. same general .locality aS the "-22-A-121" sample; above. Cor~sistS of phlogopite-magnetite-bornite- +/-?. 37-A GMC DATA REPORT 3 4.8 ~ Page 117/127 TM-o4-~ o-~ 2-22-a-1 2s: .Specimen from the same general locality as the °-22-A-121" sample, above. Consists of magnetite-chalcopyrite- +/-?. TM-04-1 0-1 2-22=A-t29: Specimen from the same general locality as the "-22-A-121" sample, above. Consists of magnetite-pyroxene --> phlogopite/tremolite-actinolite/? -chalcopyrite-bornite (trace amount).. Features chalcopyrite. and calcite on planar/vein-like surfaces as well. TM-04-1 0-1 2-22-A-1 30: Specimen from the same general locality as the "-22-A-121." sample, above. Consists of magnetite-phlogopite-chalcopyrite- +/-?..Magnetite varies in crystalline/grain size. TM-04-1 0-12-22-A-1 31 .Specimen. from. the same general locality as the "-22-A-121" sample, above. Consists of magnetite-forsterite/serpentine/ +/-?. T'nlt-04-1 0-12-22-A-1 32: Specimen from .the. same general locality as the "-22-A-121° sample, above. Consists of magnetite-bornite (trace amount)-phlogopite-:calcite- +/-?. TM-04-1 0-1 2-22-A-1 3.3: Specimen from the same general locality as the "-22-A-121" sample, above. Consists of phlogopite-serpentine-magnetite- +/-?. TM-04-1 0-1 2-22-A-1 34: Specimen from the same general locality as the "-22-A-121 ° sample, above. Consists" of magnetite-phlogopite-chalcopyrite-bornite- +l-?. TM-04-1 0-12-22-A-1 3g: Specimen from the same general locality as the "-22-A-121" sample, .above. Consists of magnetite-phlogopite-calcite. Apod/lens of crystalline calcite was noted occuring within magnetite crystals in one location in the specimen. T M-04-1 0- 1 2-22-A-1 36. .Specimen from the same genera) locality as the "-22-A-121" sample, above. Consists of magnetite-phlogopite-calcite- +/-?. TM-04-1 0-1 2-22-A-1 37: Specimen from the. same general locality as the "-22-A-121" sample, above: Consists of pyroxene(?)-phlogopite-magnetite(?)-chalcopyrite-bornite-malachite-azurite-calcite- +1-?. Complex sample. TM-04-1 0-1 2-22-A-1 38: Specimen from the same .general .locality as the "-22-~-.121" sample, above. Consists of magnetite-phlogopite-calcite(?)- +/-?. TM-04-1 0-1 2-22-A-1 39: Specimen from the same general Locality as Che "-22-A-121" samp[e, above., Consists of pyroxene(?)-magnetite-forsterite{?)/serpentine{?)/calcite(?)- +l-?. 38-A GMC DATA REPORT 3 4 8 page ls/127 TM-04-10-12-22-B-104:. A ~(ERY NICE SPECIMEN. "skarn"; "intrusive"/"front", "zoned". CQliected in the vicinity of the skarn "apophysis"/"lens" at the north edge of the Arctic Chief. (west). pit entrance. A "co pate float" sam to -from .below "ma #3" ie. ` TM-04-6-9-3 iocalit . p p ( ) Y 9 .Specimen is approximately 16 cm in its maxirnum/"longest" dimension. Displaying six apparently recognizable individual/discrete "zones", .as followsc Zone: 1. 3.7 cm inapparent width, as measured.on thespecimen surface selected for study.. Periclase (brucite) marble,. with minor/trace spinet(?), +/-?. Light grey, "banded". Zone 2. About. 2.0 mm "wide". Clear-grey. Coarse .crystals of quartz(??), calcite(?), in a lens-like "border" region between zones. 1 and 3. Zone 3. On the order of 4.0 mm "wide". Dark grey-greenish-yellowish. Banded. Calcite(?), forsterite(?), pyraxene(?), +/-?: Zone 4. About. 5.O mm "wide". Ayellowish-greenish zone. Forsterite(?}, +/-?; calcite(? ). Zone 5. On -the order of 13.0_ mm "wide". Dark greyish. Pyroxene(?), phlogapite(?}, other "micaceous" mineral(s)(?), +/-?. Zone 6. Approximately 16.0 mm in apparent 4vidth, as measured across thin "tongue-tike" feature .which is surrounded by .immediately-adjacent zone 5 material Pinkish in color. Likely(?) 'altered igneous material -- ie. zoisite(?)/clinozoisite(?)tepidote(?}/+/-??; or garnet(??), calcite(??}, +/_??, This "illustrative" specimen is moderately-strongly fractured, with most of the evident fractures oriented more or less sub-perpendicularly to the "borders/margin" of the "apophysis/intrusive(?)/replacement. zone ("6"), wherein the "skarn" material presently occurs. This tatter perhaps/likely .associated with a "long-lived" (or otherwise) fracture, oriented along the (apparently, in this. view) .long .axis direction of the. present mass of "skarn" and related zones surrounding the garnet, +/ ; "core". (?). This is the specimen described by S M Aieksandrov in his paper "Gold Behavior during Ertdogenic ar~d S~aunraene Alteratian of Sulfides in Magnesian Skarns" BY S M ALEKSANDRO'Vs PUBLISHED IN GEOCHEMISTRY INTERNATIONAL,- 2007, VOLUME 45. No. 2, pp. 152-169. The following is taken from remarks of TCM, in his "review" of this paper, in the present report (above, pp. 7-9, which cf.): ........: Among others, one important point in particular seems worthy of special note here in ..this commentary. On page 154,. Aieksandrov observes: "The magnesian skarns of the Arctic Chief deposit occrar~ not only at contacts with the [main] intrusion but also around injections of diorite melts into dolomites (Fig. 2). The rocks preserve their zoning and inclusions of Mg- ludwigite in the forsterite calciphyres but contain no magnetite ore mineralization" jassociated directly with the latter, smaller/miner `injections', ie.]. Illustrative of this, his. Figure 2, on his. page 156, offers a drawing of a rock specimen. This specimen happens to be the one designated `? M - 0 4 - 1, 0 - 1 2 - 2 2 - B - 1 0 4" when it was collected in the field. at the Arctic Chief on Jctoberl2, 2004, at sampling locale "22-B". ` Described;by TCM in his "triage" phase of analysis. as a "VERY NICE SPECIMEN", among other comments. This specimen was subsequenty sent in :its entirety to Aieksandrov. Studied, depicted. and discussed, by him.. Who also apparently found it a 'very nice specimen'. Collected-in the near vicinity of a larger skarn/apophysis/lens. of tongue-like aspect,. featuring zoned igneous and "skarn" materials within carbonate host rocks, with green, ttue, +I-, "rusty"-/copper-staining present in places abng its margins. This larger featur~;~is a 39-A GMC DATAREPORT 3 4 8 Page 119/127 rather "gaudy"!spectacular one; well-photographed, 2004 and later. As well as, subsequently, in 2006, collected in detail as samples. "TM-06-8-22-2-........". Cf. "maps, descriptions, etc. by TGM in the "Data Supplement" of the present report Location is at the northern edge/margin of the entrance cut of the Arctic Chief (west). pit, exposed up on the side/wall of the cut. In the .vicinity of the core/crest of a tight/overturned fold in the carbonate host rocks. Below map#3 (ie. TM-04-6-9-3 locality). (From selected portions of..earlier letters from SMA to TCM: "Ludwigite is in serpentine-bearing marble ~ M - (0 4 j - 1 0 - i 2 - 2 2 - B - 1 0 4, very .little. May be in contact with marbles you can see kotoite Mg3(B03)2???......." "You can see rhythmically-banded textures, that inherit, and in magnetite ores.. (The -best you can see in T M ~ 0 4 - 1 0 - '1 2 - 2 ,z - b - 1 0 4 --- (the sequence( around diorites'. injection in marbles: exchanged ("altered"] diorite--clinozoisite rim-- pyroxene skarn--banded ludwigite-bearing forsteritic calciohvre--banded periclase - {brucite) marble.) According to its caption, Aieksandrov's Figure.. 2 illustrates "diorite injection in dolomite and zoning in magnesian skarns"........... Recognized as such in the field, too.- Collected with - precisely. this intent, this specimen is used as an example -- "in microcosm", as it were -- of the general relationships ("positions") typical of magnesian skarns, at various scales from hand specimen, as here,. through "deposit scale"."Per the "model" for the "geochemistry of skarn and ore formation in dolomites" as developed and set forth by Aleksandrov and his associates over. a period of many years. Providing further illustrative bonuses, as observed, and depicted, this informative specimen- also features "rhythmically banded forsterite calciphyres", and "disseminated. crystals of magnesioludwigite". In addition to the other compositional and textural features .characteristic. of magnesian skarns so nicely displayed in this one specimen. Collectively, "Letting the rock speak for itself", as it were....._:.. This Figure ,this specimen, the evidence afforded, supplemented by Aieksandrov's comments, sufficiently informative to merit incorporation in the present report. A '`key" item..- Thus his Figure 2 and caption are reproduced below, on page "Insert//SMA-156": 40-A AMC DATA REPORT 3 4 8 Page 120/127 156 ALEKSANDROV ~ ~ ~ - r _ _ _ ~ i ~~ ._ i :.. Il /l 111 \~~~~~~\~~~~~~/// ~ ~____-__=~>~////rl IIII II)I fJlll /1il/ ))1,11/////7i ~~ .: -- -_ ~ ~/i/ Zo ~11~1~11:1.11\II1l1111///l~~i/ //////ij` _ "' -~ 1~II~II.1'tir~\\11\I1,\'\+'i\\11!`~~ ~/,,,//i°// F'h / 1 11111 1\11\\ \ ~'\\\\\ 1111 1111 1/ 1 ~~II,ILd' \1\ \\\\. \\\\\~1\4 ull'rlllll L /l ~i1i ~~'\`i\1111 `\i\li\';\~ 1\ ii iFoCa' 1''~I\'~\ ~ 3 5 %I \\ \\\\~ \\111 \~\\;.`\\.1\,\\\\ \~ \\~` \ %/~~~.\~~\\\ '~/// \ \\\\~\~\ ~ \ \ ~\~ \\\~~~~.~~~:_~i////~/ink\\ u .. / I 3 I1/////I l 1111 ///// 1 ~ /II I'f•~ll~\\\ ~i/////~1111\\1' i~ 1l/l/'/ ///lll'1//I ~ 1 1\1111\\F'ii ~ 5%ii/I//A1 ~\~\\• ~i / i r / / 1111111\\~ Itil~~\~~~`~i~/// \ ~~~_ Fig. 2. Diorite injection in dolomite and zoning in magnesian skarns. Arctic Chief deposit (sample of T.C. Mowatt). {1) Diorite re laced b zoi 't p y st e (Zo); (2 hlo o ite-dio side s P g p karn Ph ; 3 dio side skam D' • 4 r a p ( ) O t , h mlJC 11 banded forste p ( ) O me calci h r Y~ Y PYe (FoCa); (5) disseminated crystals of magnesioludwigite (Ld). Magnification 2.5x, ((INSERT//SMA-~ 56}) 6MC DATA REPORT 3 4 8 Page 121/127 TM=04-1 0-1 2-22-13-1 1 4: Specimen from the northwestern part of area "22-B", at the northwest side of the Arctic Chief (west) pit entrance. This is below map {ocale #3. A "#loat" sample. Features a "plug-tike" zone/lens/tongue of "skarn" into/surrounded. by carbonate "host/country" rock. Presumably (?) fracture-related. "Skarn" consists. of apinkish-brownish. garnet "core' ; rimmed with a "calcite+magnetite(?)+pyrte+garnet" zone, featuring relative concetration of magnetite(?) pyrite(?)- +/-?: The carbonate rock -- pertclase (brucite) marble -- is white-fight grey. It consists of the rock-forming assemblage of calcite and periclase (brucite), with. minor-trace. amounts of associated pyrite (euhedral, +/-), magnetite(?)/mol~rbdenite(???). +/- .graphite(??). Specimen contains some fractures, best observed on weathered.-surfaces. TM-04-1 0-1 2-22-B-'1 1 5: A "float" sample, from locality "22-8", below locality "3" at the. northwest side of the .entrance to-the Arctic .Chief (west) pit. Features a "skarn° plug/lens/tongue into carbonate host rock. The larger of the two broken pieces was sent to SMA, the smaller piece, containing the "snout" of the plug{lens, was retained. The carbonate host rock is a white periclase (brucite} marble, with trace amounts of associated graphite(?)/mo~bdenite(???). pyrite, and spinet(?). The "skarn" material(s) islare dark grey-blackish; pyroxene(?)-magnetite(?}- sulphides (pyrite?, +/-?), as well as aminor-trace amount of reddish-pinkish-brownish ...garnet. TM-04-1 0-1 2-22-B-1 1 6: A "float" sample, from .locality "22-B", below locality "3" at the northwest. side of the _ entrance to the Arctic Chief (west) pit. Specimen: features serpentine, with a seam{vein of white (calcite?) and .dark grey/black material(s), Pyroxene(?}, .serpentine, forsterite(?), epidote(?), calcite, magnettte(?)fother black opaque .mineral(s)(?); trace of sulphides(??}. TM-04-1 0-1 2-22-B-1 1 7: A "float" sample, ftom locality "22-B", below locality "3" at the northwest side of the entrance to the Arctic Chief (west) pit. An "alterered/retrograded" pyroxene skarn material(?): pyroxene --> tremalitic/ actinolitic: apmphibote//talc(?}/+/-?. With some calcite(?) and sulphides (pyrite?}: -TAA-04-1 0-1 2-22-B-1 1 8: A "float" sample,. from locality "22-B", below .locality "3" at the northwest side of the entrance to the Arctic Chief (west) pit.. An "illustrative" specimen. Specimen is about 11.0 cm in its "longest" dimension. "Banded/zoned", as follovrs: Zane 1. 15 mm in apparent width, as measured on the face setected for study. A plagioclase- pyroxerte rock;- a "dioritic", or "endoskarn" material(?). Zone 2. 4.3 cm "wide". Pinkish .garnet. Zone 3. 3.5 cm "wide". Pyroxene, moderately altered. to tremolitic/actinolitic .amphibole(?), +/-?• Zone 4. 1.5 cm "wide". Phlogopite. :Zone 5. 1.5 cm "wide". Forsterite(?)/serpentine(?)/+/-?; spinal(?), maroon-red- brown. "magnetite/hematite(?)", black opaques. 41-A Page 122/I27 GMC DATA REPORT 3 4 8 TM-04-1 0-i 2-22-B-1 i 9': A "float" sample, .from locality '`22-B"; below locality "3" at the northwest side of he entrance. to the .Arctic Chief (west) pit. Periclase (brucite) marble. With associated "black-smoky" spinal(?)/or some other more or less opaque mineral(?), occurring as eu-subhedra (tetrahedra?/cubes?/+/-?). ["Borates"??1. This. "spine)/opaques/?" material(s) comprises an appreciable (+/-30°Io ?) component of this specimen. TM-04-i 0-1 2-22-B-i40: A "float" sample, .from )ocality "22-B", below Ideality "3" at the northwest side of the entrance to the Arctic Chief (west) pit. Pyroxene --> tremolitic/actinolitic amphibole - serpentine(?) -forsterite(?) - spinal(?) -trace ..garnet(?) -trace magnetite(?) -trace. plagioclase(?). Pyroxene and plagioclase sub-euhedral. "Exo-/endo-skarn"(?) - ie. "plagioclase-pyroxene rock"(?). Or...:... ? Note a concentration of chatcopyrite at one end of the specimen interarown with p~rroxene (within avroxene crystals tool and disseminated amongpyroxene and plagioclase. Specimen agoears to perhaps be °silicified" (al. TM-04-i 0-1 2-22-B-141 A "float" sample, from.. locality "22-B", below locality "3" at the northwest side of the entrance to the .Arctic Chief (west) pit. Copper mineralization at one end of the specimen. Pyroxene(?)/magnetite- phlogopite-chatcopyrite-bornite(trace.~-malachite-azurite- calcite. TM-04-1 0-1 2-22-B-1 42: A "float" sample, from locality "22-B", below locality "3" at the northwest side of the .entrance to the Arctic. Chief (west) pit. ' Magnetite-serpentine?/forsterite?/+/-?. TM-04-i 0-12-23-1 05: A fractured, banded/layered/sheeted specimen. Weathered, but with some interesting structures .and .mineral textures/intergrowths. Calcite-magnetite-chatcopyrite-malachite-/hematite(?)- +/-?. TM-04-i 0-1 2-23-i 06: Massive crystalline magnetite,. with subord'+nate ("yellow-greens) crystalline forsterite(?)-serpentine(?)- +/-?. Yellow-green, +/- some white,. crystals are intergrown among magnetite crystals, as well as along fractures in specimen. TM-04-1 0-1 2-23-1 t)8: A "granitic" rock. Float/excavated/"cast" material from the southern end of the Arctic Chief (east pit. A few fractures; three sets/directions/attitudes: noted. Some apparent(?) inclusions(?), dark as well as light. [Or, perhaps, "phenocrysts"?j. Plagioclase-pyroxene/hornblende(?)-some calcite(?}-some "rosy" quartz(?)-trace chatcopyrite; ..magnetite(?). A few fractures -- some.. with chalcoPrite, +/-. Others with: dark green crystalline material, +/-. Fractures bordered by "leuco"/light-colored. zones ("bleached"?) -mostly III plagioclase and/or?. 42-A GMC DATA REPORT 3 4 8 Page 123/122 °Intrusive"......... or "endoskarn"........ (?)• Appears gdioritic", an cursory examination with the stereo-microscope (?). YM-04-10-12-23-109: .Specimen represents float/excavated/"cast" material: from the southern end of the Arctic Chief (east pit. A "granitic" ("dioritic"} rock.. Texture igneous, or recrystallized! metamorphic, or "contaminatedA more leucocratic intrusive magma(?). Intrusive, or endoskarn, or...... (?). Fractured, with "bleached" border zones, greenish vein-filling epidote. - Plagioclase(twinned)-pyroxenelhornblende(?)-quartz(???)-calcite(??), magnetite (??).:Trace chalco~yrite. A "plagioclase-pyroxene" rock, apparently; of one. sort or another. Apparent(?) igneous crystallization textures, vrith plagioclase and pyroxene(?) eu- subhedra intergrown. Some retrograde(?) chlorite/serpentine(?)-- (after pyroxene?). . Some plagioclase.. crystals.. feature "cores" of greenish crystalline (epidote?/+l-?} material(s) (altered anorthite-rich .cores, ar ??). TM-04-10-12-23-T1 O: .Specimen represents float/excavated/"cast" material from the southern end of the Arctic ...Chief (east pit.. "Dioritic" rock.: Plagioclase (sub-euhedra, twinned), pyroxene: (sub-euhedra), epidote (espei;ially as alteration product in central/core locations in plagioclase crystals). Sorne °rosy" pinkish. quartz(?} here and there. Trace Ryrit~~) with a few crystals of agAarent cube gvritohedron aspect adjacent to ~la4ioclase and pyroxene as individual grains tsome noticeably striated). A few fractures cross the specimen, with associated dark green-black (chlorite?, +/-?) material(s) as "filings". Some interesting textures, with apparent igneous character of intergrown plagioclase.. and .pyroxene rock-forming minerals. TM-04-1 0-1 2-23--1 11 : Specimen .represents float/excavated!"cast" material from the southern end of :the Arctic Chief .east .pit. An altered. "granitic" rock. Actually "dioritic", .featuring pyroxene {altering/ed to chlorite, +/-), and plagioclase (alteringled to clinozoisitelzoisite/epidote, +/-). Trace mo~lbdenitel??)..magnetite(?): A few fractures, with associated epidote, +/-. 43-A 4 127 e 12 Pa / 9 6MC DATA REPORT 3 4 8 . M. ALEKSANDROV : ERVATIONS ON SPECIFIC SPECIMENS S ) THER'OBS 0 ~ "First commentaries for your. samples: Common look - as also in Brooks Mountain and. Tin Creek. [Seward Peninsula, Aiaska] in Arctic. Chief rocks. [Emphasis by TCMj ...... in TM-04-10-~2-22-a-134 and 131 and -102 --- banded phlogopite-- 'magnetite ores,:- in -126 --- serpentinelfarsterite rhythm in magnetite; in T M - 0 4 - 6 - 9 - 4 - 2 --- is forsterite--calcite rhythm, etc....). These textures. hava origin on progressive stage of metasomatic exchange of dolomites and reflected in ores-- see book [SMA, 1998j, pages 77-87. It is non-equilibrium process." " In dour collection is splendid _.periclase marbles but in literature are not this information: In many samples in marbles and forsterite-calcite environrnent are a bit to .big black crystals of LU®WIfa1TE ts~e TM-04-10-12-22-b-115; -23-110, ~23-108, etc See Brooks Mountains Thin fully are not in literature about Whitehorse copper beltl [Underlining in above is original in letter from SMA; bold emphasis added by TCM.j About typical lime skam (T M - 0 4 - 0 8 - 0 9 - 2 ~ (ofj pyroxene-garnet composition: What is its. position. with magnesian skarns? I believe that it has postmagmatic origin from Si-bearing marbles. What, how much, are sulfides in this type skarns?? Or. absent? In forsterite marble (T M - 0 4 - 6 - 9 - 5 - 1) is spinal. The part of pyroxenes is Al-bearing. In this situation is formed late phlogopites in rocks and ores ............. About dykes and. its composition. In :last letter I note about leucocratic hornblende quartz. monzonite dyke. tt is possible that monzonite from massif will be more. basic! If this so /welt -then/ you can think-that monzonite magma of massif is result of assimilation of host rocks and primary melt was more close, to granitic. composition and was superheated.. Last dykes from deepest magmatic camera must be leucocratic. In book [SMA; 1998] (Fig. 13) is illustrated this, and similar with. Arctic Chief locality. [Emphasis by TCMj. (!n text, epidote = clinozoisite). Plus, see green amphibole with plagioclase in quartz-monzonite dyke- T M- 0 4 -1 0 -1 2- 2 3 -1 0 8, 1 10 with pyroxenes and quartz." TM-05-5-25-1 -Q: "Probably in this specimen is ludwigite in the. marble part near contact with forsterite- magnetite ore. ...,......" "Marble with ludwigite (??????) as black needles. ......:....." "I wNl be send .you new j[microprobej] analytical data for sample..#TM-05-5-25-1-Q (marble with Ldw?????? and + magnetite. ore............ )" [An excerpt from a letter from SMA to TCM, May 11, 2006 states: "All black needles are pseudomorphoses magnetite after boraces ....:.......Hj 44-A - 6MC DATA REPORT 3 4 8 Page i25/z2z ".Other minerals in this .specimen: Mg-bearing.. magnetite- (>90% FsO, and 1.5% MgO) Dolomite- {22% MgO, 30% CaO) Serpentine- (36% MgO, 3% FeO, 45% SiO2) Phlogopite, altered to clinochlore- (with MgO, SiO2, and AI2O3} Talc- (MgO, SiO2} Are jalso} Fe-Mn species dolomite/artkerite." "Near manzonite plag and prx -- transformed into zoisite and calcite; and prx -- into Mg phlogopite. Ail periclase in marbles fully transformed to brucite, with calcite; its form is pseudomorphic after periclase. In these rocks are a few grains of forsterite and. clinohumite. In .magnetite ores forsterite is transformed inta serpentine near calciphyres, or into other silicates --- into Mg-phlogopites {after diopside). Mg-pyroxene is in T M - 0 4 - 1 0 - 1 2 - 2 2- A- 1 37 and actinolite........ 2 2- B- 1 1 7, amphiboles........ 2 2- A- 1 0 7 .Green amphibole with plagioclase in quartz-monzonite dyke- TM-----23-108, 110 - with pyroxenes." "TM-04-8-9-2-Z: Vesuvianite (idocrase)-pyroxenic typical barren. skarn: TM-04-1 0-1 2-22-A-1 01: Actinolite in magnetite ore. TM-U4-1 0-1 2-22-A-1 1 3: Brucite-periclase marble, with forsterite and clinohumite. Microprobe. analysis: P-68-2. Brucite .and periclase, some dolomite. TM-04-1 0-1 2-22-A-1 21: Phlogopite in magnetite ore. TM-04-1 0-1 2-22-A-1 26: Rhythmically-banded serpentine-magnetite ore. TM-04-1 0-1 2-22-A-1 30: Magnetite ore .with phlogopite. TM-04-1 0-1 2-22-A-1 31: Magnetite ore with phlogopite; magnetite is prismatic. TM-04-1 0-12-22-A-1 32: Magnetite ore with .phlogopite; magnetite is prismatic. TM-b4-1 0-1 2-22~-A-1 33: Phlogopite-magnetite ore. T.M-04-1 0-1 2-22,.A-1 34: Magnetite ore with phlogopite; magnetite is prismatic. 4 5- A 6MC DATA REPORT 3 4 8 Page 26/i2~ TM-04-1 0-1 2.22-A-1 35: __ __. Magnetite ore with phlogopite; magnetite is prismatic. _TM-04-1 0-1 2-22-A-1 37: Diopsidic skarn with .prismatic magnetite. TM-04.1 0-1 2-22-B-1 04: Forsterite-bearing... brucite (after periclase) marble, with calcite, serpentine and phlogopite.`. .Microprobe analysis: P-67-2. Forsterite, serpentine, Brucite, phlogopite. TM-04-1 0-1 2-22-B-1 14: Rhythmically-banded serpentine-magnetite ore, Serpentine after forsterite. TM-04-1 0-1 2-22-B-1 1 7: Actinolite after diopside, in magnetite ore. TM-04-1 0-1 2-22-8-1 1 9: Brucite-periclase marble. Microprobe analysis: P-68-1. Brucite with rEaicts of periclase, and dolomite + spine( + hydrotalcite (after. spinet) and. magnesite. TM-04-1 0- 1 2-22-B-1 41: Magnetite ore with serpentine. TN1-04-i 0-12-23-106: Rhythmically-banded serpentine-magnetite ore. Serpentine after. Forsterite. TM-04-10-12-23-108: Plagioclase rock with amphibole (dike???). TM-04-10-12-23-109: Clinohumite calciphyre .with. magnetite. TM-04-10-12-23-110: ..Plagioclase rock with hornblende and pyroxene (dike?). TM-04-10-12-23-111: Skarned zone on contact with .dike. Content anorthite, pyroxenes (fassaites) and garnet. The typical in contact. magnesian skarn plagioclase-pyroxene composition and secondary [-ily] transformed in [into] salite-garnet bearing associations. Microprobe analysis: P-67-1. Salite, plagioclase (anorthite), garnet: (grossularite 70%, andradite 30%), pyroxene. TM-04-1 0-1 2-23-B-1 15: Brucite (after periclase) marble with forsterite. T.M-05-10-13: Rhythmic-banded marble with sulphides." 46-A GMC DATA REPORT 3 4 8 Page 127/i2~
