Unnamed Occurrence (ARDF - ID175; west of Julian Creek), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence consists of arsenopyrite-bearing quartz veinlets in a sericitically altered, granodiorite intrusion in flysch of the the Upper Cretaceous, Kuskokwim Group (Miller and Bundtzen, 1994; Bundtzen and Miller, 1997; Miller, Bundtzen, and Gray, 2005). The intrusion has a 40K/40Ar age of 70.1 Ma. The quartz veinlets occur in an area about 130 feet square. Grab samples of the veins contained up to 10.0 parts per million (ppm) silver, 100 ppm tin, more than 2,000 ppm arsenic, 11.0 ppm bismuth, 3.3 ppm cadmium, and 12 ppm antimony (McGimsey and others, 1988). The mineralized zone is a possible source of the placer gold in Julian (ID177) and Spruce (ID176) Creeks.
Workings: Samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in the 1980s (McGimsey and others, 1988).
Age: Unknown; the host intrusion has a 40K/40Ar age of 70.1 Ma (Miller and Bundtzen, 1994).
Alteration: Sericitic alteration of granodiorite.
Commodities (Major) - Ag, Sn; (Minor) - As, Bi, Cd, Sb
Development Status: None
Deposit Model: Sn-polymetallic deposit or Polymetallic vein (Cox and Singer, 1986; model 20b o
3 entries listed. 2 valid minerals.
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Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286. McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.