Pupinski Prospect, McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Pupinski prospect is located near the saddle north of Encio Gulch at an elevation of 1,500 feet (457 m) in Section 18, T. 26 S., R. 22 E., of the Kateel River Meridian. The reporter visited the site in 1989 and 1996.
Geology: The Pupinski prospect is along the southeastern margin of the Nixon Fork monzonite stock (Bundtzen and Miller, 1997). It consists of a magnetite-sulfide skarn that differs from the Nixon Fork Mine showings (MD062) in that gold is absent and copper, silver, tin and minor tungsten values are elevated. Cassiterite is locally abundant in late stage veins, and in association with tourmaline. The Pupinski deposit has only been briefly explored. Age of mineralization is probably Upper Cretaceous based on isotopic age (68.0 Ma) of Nixon Fork pluton (Moll and others, 1981; Bundtzen and Miller, 1997). Grab samples collected at the site contain up to 262 ppm silver, 3.00 percent copper, 0.35 percent tin, and 120 ppm tungsten (Bundtzen and Miller, 1997; Ted Almasy, personal communication, 1998).
Workings: The Pupinski deposit has only been briefly explored, mainly by Central Alaska Gold Company in the early 1990s (Ted Almasy, personal communication, 1998). Grab samples collected at the site contain up to 262 ppm silver, 3.00 percent copper, 0.35 percent tin, and 120 ppm tungsten (Bundtzen and Miller, 1997; Ted Almasy, personal communication, 1998).
Age: Age of mineralization is probably Upper Cretaceous, based on isotopic age of Nixon Fork pluton (Moll and others, 1981).
Alteration: Sericite and tourmaline.
Reserves: None.
Commodities (Major) - Ag, Sn; (Minor) - Cu, W
Development Status: No
Deposit Model: Polymetallic tin (Cox and Singer, 1986; model no. 20b)
Mineral List
5 entries listed. 4 valid minerals.
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References
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.
