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Home My WebLink AboutGMC Data Report No. 265 X-ray fluorescence trace element data of the U. S. Bureau of Mines Idaho Gulch (Tofty tin belt) core of Central Alaska. r~ GE~OZQ '~ ~ ~/ ÇI:) 0 ~¡ALS Received 5 February 1996 Total of 2 pages in report Alaska Geologic Materials Center Data Report No. 265 MEMORANDUM State of Alaska DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGICAL AND GEOPHYSICAL SURVEYS TO: John Reeder DATE: February 5, 1996 Curator Geologic Materials Center FILE NO: TELEPHONE NO: 451-5000 FROM: Karen H. Clautice,~t} Geologist SUBJECT: Analyses of Tofty core Below are analyses made by Rainer Newberry, UAF, of splits we took from drill core from the Geologic Materials Center last spring. I have added brief sample descriptions. The core came from wooden boxes labeled "Idaho Gulch" and "Tofty." It is my understanding that this core was collected by the U.S. Bureau of Mines in 1956 during a study of the Tofty tin belt, approximately15 Ian northwest of Manley. The only published USBM data I can find from that era is chum drill data from placer deposits (Thomas, 1957). In the 1980's, the USBM did additional work in the Tofty area, logged 1956 core and published geologic cross sections constructed from the drill core data (Warner and others, 1986). The core I sampled was part of this study, I believe. But I was not able to entirely correlate the diamond drill hole numbers and footage found on the wooden core boxes to the footage descriptions and hole numbers in the 1986 report. The below listed samples are labeled as I found them in the wooden boxes at the GMC. I suggest anyone interested in the results read the report, look at the core and make their own interpretations as to location. Warner and others, 1986, suggest the presence of a carbonatite, an uncommon carbonate intrusive rock, in the Tofty area. Based on the theses analytical results, Newberry concurs. The highest niobium values come from a rock that looks like a sample from the carbonatite at Magnet Cove, Arkansas. These samples are within the area of the geophysical surveys to be released this month. We will have a field mapping crew doing follow-up work to the surveys this summer in the Tanana B-1 Quadrangle, northeast of the Tofty area headed by Rocky Reifenstuhl. Trace element analyses were performed by Rainer J. Newberry in the University of Alaska X-ray fluorescence spectrometer laboratory. Approximately 7 g of minus-200-mesh sample material was pressed into flat disks for analysis by a Rigaku® wave-length-dispersive X-ray spectrometer using procedures developed by the Alaska Division of Geological and Geophysical Surveys for data acquisition and correction. Three analyses of each pressed-powder disk were conducted and estimated errors due to counting statistics are noted in the column headings. GMC Data Report No. 265 1/2 (John Reeder)) Page 2 February 5, 1996 Drill NB RB SR Y ZR BI MO SB SN W GA NI PB TH ZN Hole Interval ±2 ±3 ±5 ±2 ±10 ±1 ±1 ±1 ±1 ±1 ±1 ±3 ±5 ±2 ±3 ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm DDH3 5' 183 34 38 4 37 0 6 6 4 0 11' 3416 33 56 638 DDH3 29.8' 5 1 29 1 8 1 1 4 0 0 19 1201 3 2 81 DDH3 46' 100 2 37 34 266 1 5 0 1 0 26 20 11 6 142 DDH8 200' 64 0 1975 39 250 0 6 0 0 0 2 53 0 0 41 DDH10 45.7' 194 0 7245 30 247 0 6 0 0 2 1 38 0 0 32 DDH12 204.7' 542 0 3411 24 281 0 7 0 0 0 2 39 0 0 33 DDH 3 5' magnetite-bearing limonite DDH 3 29.8' gray-green phyllite DDH3 46' tan, fine-grained carbonate with 2mm wide dark red-brown and orange limonite veinlets DDHa 200' magnetite to 1 cm acro~s in light orange~tan, fine-grained carbonate, DDH10 45.7' magnetite-bearing, white medium-grained carbonate with quartz veins DDH12 204.7' magnetite-bearing, white medium-grained carbonate Note: All samples described as 'carbonate' behave like a dolomite with HCI, effervescing only after being scratched Thomas, Bruce, Tin-bearing placer deposits near Tofty, Hot Springs District, Central Alaska: U.S. Bureau of Miners RI 5373, 56 p. Warner, 1. Dean, Mardock, C.L., and Dahlin, D.C., 1986, A columbium-bearing regolith on upper Idaho Gulch, near Tofty, Alaska: U.S. Bureau of Mines IC 9105,29 p. cc: Rainer Newberry, UAF Milt Wiltse, DGGS Rocky Reifenstulù, DGGS GMC Data Report No. 265 2/2