Unnamed Occurrence (ARDF - ID048; east of upper Little Yetna River), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence is a zone of bleached, silicified rhyolite of unknown extent; the silicification is largely chalcedony. The rhyolite is part of the Upper Cretaceous or Early Tertiary, Yetna River volcanic field (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). One grab sample of silicified rhyolite contained 100 parts per billion (ppb) gold and 60 ppb mercury (McGimsey and others, 1988).
Workings: Samples were collected by the U.S. Geological Survey in 1985 (McGimsey and others, 1988).
Age: Unknown; the rhyolite of the altered zone is part of the Upper Cretaceous or early Tertiary, Yetna River volcanic field (Miller and Bundtzen, 1994).
Alteration: Silicification with deposition of chalcedony.
Commodities (Major) - Au; (Minor) - Hg
Development Status: None
Deposit Model: Hot springs gold-silver? (Cox and Singer, 1986; deposit model 25a).
1 entry listed.
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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.