Unnamed (along Kuskokwim River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb
Other commodities Ni
Ore minerals pyrite; pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale D-6
Latitude 62.888
Longitude -155.588
Nearby scientific data Find additional scientific data near this location
Location and accuracy The unnamed occurrence is located along the banks of the Kuskokwim River about 8 kilometers due south of McGrath, Alaska and 1.5 kilometers due south of VABM About, at an elevation of about 400 feet (120 m) in the SE1/4 sec. 2, T. 32 N., R. 34 W., of the Seward Meridian. The occurrence corresponds to prospect #1 of Cobb (1972) and prospect #13 of Bundtzen and Laird (1983; field no. 77BT230).

Geologic setting

Geologic description

This occurrence consists of pyrite-pyrrhotite nodules in highly deformed, sheared shale and siltstone of the Late Cretaceous Kuskokwim Group (Bundtzen and Laird, 1983). Individual sulfide nodules average about 8 centimeters in diameter, and are locally oxidized to ferricrete gossan. The sulfide bearing zone, which appears to be parallel to steeply dipping bedding in the host sedimentary rocks, is about 3 meters thick. The sulfide zone quickly extends upward into the vegetated slopes (Bundtzen and Laird, 1983). Cobb (1972) and Brooks and Martin (1921) refer to the occurrence as an unnamed, copper-nickel lode. A selected grab sample reported by Bundtzen and Laird (1983) contains 12.26 grams/tonne silver, 116 ppm copper, 167 ppm lead, and 139 ppm nickel.
Geologic map unit (-155.59034366047, 62.8873713911565)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Alteration of deposit Ferricrete oxidation of pyrite and pyrrhotite.

Production and reserves

Workings or exploration Brooks and Martin (1921) first mentioned the existence of sulfide mineralization at the site. A selected grab sample reported by Bundtzen and Laird (1983) contains 12.26 grams/tonne silver, 116 ppm copper, 167 ppm lead, and 139 ppm nickel.
Indication of production None
Reserve estimates None.

References