Von Frank - North Occurrence, McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Von Frank - North occurrence is situated on a southwest spur of Von Frank Mountain at an elevation of approximately 2,800 feet (853 m) in Section 36, T. 22 S., R. 23 E., of the Kateel River Meridian. The prospect was located on a 1:63,360 scale map by Clautice and others (1993), and is accurate to within 250 feet (76 m).
Geology: Thin stockwork-type arsenopyrite-pyrite veins developed in granodiorite at the west side of Von Frank Mountain intrusion. No dimensions or aerial extent are given (Clautice and others, 1993; DiMarchi and others, 1994) The age of mineralization is Late Cretaceous, based on inferred age of 70.0 Ma Von Frank Mountain pluton (Patton and others, 1980; Moll and others, 1981). In 1992, Clautice and others (1993) collected grab samples of intrusive-hosted mineralization, which contained up to 78 ppb gold, 192 ppm antimony, and 100 ppm cobalt.
Workings: In 1991, Central Alaska Gold Company began a sampling program and encountered auriferous mineralization in a border phase of the Von Frank Mountain intrusion (DiMarchi and others, 1994). In 1992, Clautice and others (1993) collected grab samples of intrusive-hosted mineralization, which contained up to 78 ppb gold, 192 ppm antimony, and 100 ppm cobalt.
Age: The age of mineralization is Late Cretaceous, based on inferred age of 70.0 Ma Von Frank Mountain pluton (Moll and others, 1981).
Alteration: Sericite-quartz-ankerite in intrusion.
Commodities (Major) - As, Sb; (Minor) - Au, Co
Development Status: No
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model no. 22c)
3 entries listed. 3 valid minerals.
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Clautice, K.H., Bowman, N.D., Clough, J.G., Gilbert, W.G., Kline, J.T., Smith, T.E., and Blodgett, R.B., 1993, Land selection Unit 8 (Kantishna River, Ruby, and Medfra quadrangles); References, lead isotope, geochemical and major oxide data: Alaska Division of Geological and Geophysical Surveys, 42 p., 1 sheet, scale 1:250,000. DiMarchi, J.J., Weglarz, T.B., Adams, D.D., Huber, J., and West, A.W., 1994, Annual Report for 1993--Doyon Option Lands, Volume 1: ASA Inc. Report, 187 p. (Report held by Doyon, Limited, Fairbanks, Alaska.) Moll, E.J., Silberman, M.L., and Patton, W.W. Jr., 1981, Chemistry, mineralogy, and K-Ar ages of igneous and metamorphic rocks of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-C, 15 p., 2 sheets, scale 1:250,000. Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale.