Unnamed Occurrence (ARDF - SM033; east tributary of Kolmakof River), Aniak District, Bethel Borough, Alaska, USA

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Location: This placer occurrence is at the head of an unnamed, east tributary of the Kolmakof River that drains the western slopes of the Horn Mountains. The location of the occurrence provided by Cady and others (1955) is vague. Gray and others (1994) describe a heavy mineral placer occurrence at an elevation of about 1,600 feet in the SW 1/4 sec. 17, T. 19 N., R. 51 W of the Seward Meridian that may coincide with this occurrence. The location is approximate.
Geology: Abundant scheelite (CaWO3) and gold were found in Quaternary gravel on the western side of the Horn Mountains at some unknown location prior to 1951 and probably prior to WWI (M. Hofseth, oral communication, 1990; Cady and others (1955). Theodorakos and others (1992), and Gray and others (1994) reported values of up to 500 parts per million (ppm) gold, 20 ppm silver, and 120 ppm arsenic in panned concentrates and stream sediment samples along this creek, but no anomalous tungsten. The rocks in the vicinity consist of the Upper Cretaceous Horn Mountains pluton, the slightly older Horn Mountains volcanic rocks, and contact metamorphic rocks at the contact of the pluton and the volcanics (Bundtzen and others, 1998).
Workings: There was surface sampling by prospectors before 1951 (Cady and others, 1955). The U.S. Geological Survey resampled the area in 1988, 1989, and 1990 (Theodorakos and others, 1992; Gray and others, 1994). Bundtzen and others (1998) mapped, sampled, and described the Quaternary deposits in the area.
Age: Late Pleistocene-Holocene, based on dated glacial chronology established in Horn Mountains by Bundtzen and others (1998).

Commodities (Major) - Ag, Au; (Minor) - As, W
Development Status: No
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).

References

Bundtzen, T.K., Harris, E.E., Miller, M.L., Layer, P.W., and Laird, G.M., 1998, Geology of the Sleetmute C-7, C-8, D-7, and D-8 quadrangles, Horn Mountains, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 98-12, 38 p., one sheet, scale 1:63,360. Cady, W.M., Wallace, R.E., Hoare, J.M., and Webber, E.J., 1955, The central Kuskokwim region, Alaska: U.S. Geological Survey Professional Paper 268, 132 p. Cobb, E.H., 1972, Metallic mineral resources map of the Sleetmute quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-368, 1 sheet, scale 1:250,000. Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Dillingham, Sleetmute, and Taylor Mountains quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-606, 92 p. Gray J.E., Theodorakos, P.M., Bradley, L.A., and Bullock, J.H., 1994, Favorable areas for metallic mineral resources in and near the Horn Mountains, Sleetmute quadrangle, southwestern Alaska: U.S. Geological Survey Bulletin 2068, p. 79-90. Miller, M.L., Belkin, H.E., Blodgett, R.B., Bundtzen, T.K., Cady, J.W., Goldfarb, R.J., Gray, J.E., McGimsey, R.G., and Simpson, S.L., 1989, Pre-field study and mineral resource assessment of the Sleetmute quadrangle, southwestern Alaska: U.S. Geological Survey Open-File Report 89-363, 115 p., 3 plates, scale 1:250,000. Theodorakos, P.M., Borden, J.C., Bullock, J.H. Jr., Gray, J.E., and Hageman, P.L., 1992, Analytical data and sample locality map of stream sediment and heavy mineral concentrate samples collected from the Horn Mountains area, Sleetmute quadrangle, southwest Alaska: U.S. Geological Survey Open-File Report 92-708-A, 36 p., one sheet, scale 1:250,000.

Mineral List

Ilmenite

Scheelite

2 entries listed. 2 valid minerals.