Whirlwind Prospect, McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Whirlwind prospect is situated at the southwest end of Whirlwind Ridge at an elevation of 2,700 feet (823 m) in Section 9, T. 23 S., R. 24 E., of the Kateel River Meridian. Location is accurate to within about 1,000 feet (304 m).
Geology: The Whirlwind prospect consists of veinlets and replacement zones near the contact of a composite pluton with Cretaceous flysch. The composite pluton, which is composed of pyroxenite, gabbro, and monzonite, is elongated parallel to the northeast trending ridgeline (Patton and others, 1980). Galena and arsenopyrite occur in replacement zones at the contact and as grains in mafic phases of the pluton. The pluton is marked by an elongated aeromagnetic high (Patton and others, 1982). The Whirlwind prospect is inferred to be Late Cretaceous, based on isotopic ages of the host pluton (Moll and others, 1981). Grab samples collected by DiMarchi and others (1992) contain as much as 276 ppm copper, 1.4 ppm silver, 396 ppm lead, and 6,192 ppm arsenic.
Workings: The Whirlwind Prospect was discovered in 1991 by ASA Inc. during regional exploration on lands selected by Doyon Ltd. Grab samples collected by DiMarchi and others (1992) contain as much as 276 ppm copper, 1.4 ppm silver, 396 ppm lead, and 6,192 ppm arsenic.
Age: The Whirlwind prospect is inferred to be Late Cretaceous, based on isotopic ages of the host pluton (Moll and others, 1981).
Reserves: None.
Commodities (Major) - Ag, Pb; (Minor) - As, Cu
Development Status: No
Deposit Model: Polymetallic veins (Cox and singer, 1986; model no. 22c)
Mineral List
3 entries listed. 3 valid minerals.
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References
DiMarchi, J.J., Weglarz, T.B., Freeman, L.K., Nicholson, L.C., and Barker, J.C., 1992, Annual Report for 1992--Doyon Option Lands, Block 10: ASA Inc. Report, 121 p. (Report held by Doyon, Limited, Fairbanks, Alaska.) Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale. Patton, W.W. Jr., Moll, E.J., and Cady, J.W., 1982, Aeromagnetic interpretation of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811E, 14 pages, 2 sheets at 1:250,000 scale.
