Unnamed Occurrence (ARDF - ID138; near hill 1630), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence consists of a system of quartz-tourmaline-epidote veins in hornfels at the southern contact of a small, biotite-quartz-monzonite stock. The stock has been dated as 71.1 Ma (Bundtzen, Miller, and Laird, 1986). Major oxide data for the intrusion are given in Miller and Bundtzen (1994). The mineralized veins occupy vertical joints that strike about N40E and N44W. The size of the occurrence is uncertain. Grab samples of mineralization contain up to 860 parts per million (ppm) zinc, 300 ppm copper, 2,000 parts per billion silver, 5.1 ppm cadmium, and 10 ppm bismuth (McGimsey and others, 1988).
Workings: Samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in 1984 (McGimsey and others, 1988). Placer Dome Exploration flew an aeromagnetic survey over the Upper Granite Creek area including the prospect area in 1996. Results of that survey have not been released (L.E. Wyrick, oral communication, 2003).
Age: Undated; the quartz monzonite stock that hosts the mineralization has been dated as 71.1 Ma (Bundtzen, Miller, and Laird, 1986).
Alteration: Development of epidote-quartz-tourmaline greisen.
Commodities (Major) - Cu, Zn; (Minor) - Ag, Bi, Cd
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
3 entries listed. 2 valid minerals.
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Bundtzen, T.K., Miller, M.L., and Laird, G.M., 1986, Prospect examination of the Wyrick placer/lode system, Granite Creek, Iditarod-George mining district, Iditarod B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 86-29, 10 p., 1 sheet, scale 1:200. 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.