Unnamed Occurrence (ARDF - ID123; northwest of upper Otter Creek), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence is a zone of quartz stringers in heavily iron-oxide-stained sandstone of the Upper Cretaceous, Kuskokwim Group. The quartz stringers are next to a quartz-feldspar porphyry dike (Bundtzen and others, 1992). The dike trends northeast along the ridge. Grab samples contained up to 200 parts per million (ppm) silver, 2.00 percent lead, more than 2,000 ppm antimony, 2,000 ppm zinc, 200 ppm copper, 50 ppm tin, 1,600 ppm arsenic, 100 ppm cadmium, and 18 ppm bismuth (McGimsey and others, 1988; Bundtzen and others, 1992). The primary sulfides are entirely oxidized, but the original primary minerals probably included galena or a lead sulfosalt and sphalerite.
Workings: Surface samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in 1986 (McGimsey and others, 1988; Bundtzen and others, 1992).
Age: Undated; a nearby intrusion is 70.5 Ma (Bundtzen and others, 1992).
Alteration: Intense iron-oxide staining.
Commodities (Major) - Ag, Pb; (Minor) - As, Bi, Cd, Cu, Sb, Sn, Zn
Development Status: None
Deposit Model: Sn-polymetallic deposit or Polymetallic vein (Cox and Singer, 1986; model 20b o
2 entries listed. 1 valid mineral.
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Bundtzen, T.K., Miller, M.L., Laird, G.M., and Bull, K.F., 1992, Geology and mineral resources of Iditarod mining district, Iditarod B-4 and eastern B-5 quadrangles, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 97, 46 p., 2 sheets, scale 1:63,360. 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.