Unnamed Occurrence (ARDF - ID101; northeast shoulder of Swinging Dome), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence is a sulfide and tourmaline-bearing silicified zone at the contact between a Tertiary intrusive body and hornfels derived from the Upper Cretaceous, Kuskokwim Group (Miller and Bundtzen, 1994; Bundtzen and others, 1992; Bundtzen and Miller, 1997; Miller, Bundtzen, and Gray, 2005). The Swinging Dome intrusive is 60.9 Ma. Disseminated sulfides locally make up to 10 percent of the silicified zones. Several felsic dikes intrude the contact zone. One grab sample of mineralization contained 20 parts per million (ppm) tin, 20 ppm antimony, 40 ppm arsenic, and 2,000 ppm boron (McGimsey and others, 1988; Bundtzen and others, 1992).
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; Bundtzen and others, 1992).
Age: Unknown; the Swinging Dome intrusion that may be related to the deposit is 60.9 Ma (Miller and Bundtzen, 1994).
Alteration: Tourmaline and silicification in contact zone.
Commodities (Major) - Sb, Sn; (Minor) - As, B
Development Status: None
Deposit Model: Possibly Sn-polymetallic deposit model or Polymetallic vein (Cox and Singer, 19
2 entries listed. 1 valid mineral.
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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. 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.