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Home My WebLink AboutGMC Data Report No. 146Analytical results of K-Ar geochronology studies on biotite concentrates from the following two NPRA core tuff samples- U.S. Navy Umiat Test No. I (510.5'), and U.S. Navy Umiat Test No. 11 (488'). Received 28 November 1989 Total of 3 pages in report _ state'o~'Alask~a Geologic Materials Center Data'RePort No. 1'46~' TO: FROM: DATE: Dr. John Reeder, ADGGS Geological Materials Center, Fish Hatchery Road PO Box 772116 Eagle River, Alaska 99577 RECEIVED NOV 2,, ° Steve Bergman PRC D3136 Arco Oil and Gas Co. 2300 P lano Pkwy. Piano, TX 75075, 214-754-6264 (fax 754-3691)Div. ot c~eotegicat Su~ey 19 Novem~r 1989 Eagle River SUBJECT: NPRA core X-ray and K-Ar data It was good to visit with you last week. First, please a6cept my sincere apologies for not getting these results to you sooner. This memo provides a summary of analytical results of x-ray diffraction and 40Ar/39Ar geochronology studies on tuff beds from several-NPRA cores from the Simpson, North Simpson, Fish Creek, and Umiat wells. Enclosed please find x-ray diffraction spectra on the <2 micron fraction of 10 samples of the bentonitic tufrs. The spectra are for air dried (designated NARSA...) and ethylene glycol solvated (designated NARSG...) samples and were generated with a SINTAG PAD V X-ray diffractometer (Mike Kelton, analyst) with the following operating conditions: 45 kV, 40 mA, Cu Ka radiation, solid state crystal detector, 1 degree/min=scan rate, 0.03 degree=step size. The sample names give the well name (eg. SI _MP), core number (eg. 27), and depth or depth range (eg. 167). Also enclosed are K-Ar analytical results (Tom Bills, analyst) on biotite concentrates from two tuff samples (Umiat-gl-510.5'. and Umiat-gl 1- 488'). These two samples were the only two for which we were able to separate enough sufficiently pure and unaltered biotite for conventional K- Ar work. I thank you for your cooperation in permitting these analyses and we 100k forward to future Cooperative endeavors. GMC Data Report No. 146 Sincerely. Yours, Steven C. Bergrnan Principal Research Geologist . . _ . _ Page 1/3 GMC Data Report No. 146 Page 2/3 Sample Description & Locality: Sample ~UMIAT-1/510.5, biotite tuff. Material.Analyzed: ·Biot itc 'conc.entrate, -80/+.200 mesh.,: -_.. 40*Ar/4o K = .005538 AGE = 92.9 +/- 3.5 M.Y. Argon Analyses: 4°*Ar, ppm .03930 .04040 4O*Ar/Total 4OAr .689 .660 Ave. 40*Ar, ppm .03985 Potassium Analyses: %K 6.010 6.053 Ave.% K 6.032 '"OK, ppm 7.196 ConStants Used:. 4.962 x 10-1°/year (ke -I- k;) ---- 0.581 X 10 -m/year '. . 4OK/K = .1.193X10'-4 g/g ..... - . Note: 4°*Ar refers to radiogenic 4°Ar. M.Y. refers to millions of years. AGE = x~+(×~+ x;) In (Xe -{- ~';) X _ 4O*Ar 40K . .. - .. o. . GMC Data Report No. 146 Page 3/3 Sample Description & Locality: Sample I~UMIAT-11/488, biotite tuff core. Material Analyzed: Biotite concentrate, -200 mesh. ~O.Arl4OK = .006103 AGE = 102 +/- 4 M.Y. Argon Analyses: 4°*Ar, ppm 4°*ArlTotal 4°Ar Ave. 4°*Ar, ppm · 03524 .500 .03507 · 03490 .599 Potassium Analyses: % K Ave. % K 4.816 4.817 5.7z(7m DP 4.818 k~ = 4.962x10-~°/year AGE = ×~+(Xe+×;) In (Ne+X;) X mK +:1 ri' . NOte: 4°*Ar refers to radiogenic. Ar. -