Unnamed (east tributary of Kolmakof River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; W
Ore minerals placer gold; scheelite
Gangue minerals ilmenite

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale C-7
Latitude 61.73093
Longitude -158.57464
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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.

Geologic setting

Geologic description

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).
Geologic map unit (-158.577014344608, 61.7302233149411)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Late Pleistocene-Holocene, based on dated glacial chronology established in Horn Mountains by Bundtzen and others (1998).

Production and reserves

Workings or exploration 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.
Indication of production None

References

MRDS Number A106157

References

Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date 5/3/2003