Hill Top

Occurrence, Inactive

Commodities and mineralogy

Main commodities As; Au
Other commodities Ag; Hg
Ore minerals arsenopyrite

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale B-6
Latitude 61.44774
Longitude -157.96117
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Hill Top occurrence is located on the southwest flank of a prominent, unnamed hill east of the upper reaches of the south fork of the Oskawalik River. It is about 3.6 miles north of the Mountain Top Mine (SM058), at an elevation of about 2,200 feet, about 0.3 mile west of the center of section 30, T. 16 N., R. 48 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Hill Top occurrence consists of a rhyolite breccia zone in a felsic sill complex that intrudes sandstone and shale of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955; Decker and others, 1995). The sills are part of a large, prominent northeast-trending sill complex in the central Sleetmute quadrangle (Cady and others, 1955). One grab sample of rhyolite breccia collected by the Alaska Division of Geological and Geophysical Surveys contained 927 parts per million (ppm) arsenic, 300 parts per billion (ppb) gold, 600 ppb silver, and 2.9 ppm mercury (Robinson, 1984 [RI 84-11]; Miller and others, 1989).
Geologic map unit (-157.963526576461, 61.4470348841149)
Age of mineralization Unknown. Decker and others (1995) report 40K/40Ar ages of from 67 to 70 Ma for a nearby sill swarm that is probably similar to the sills at this occurrence.

Production and reserves

Workings or exploration The Alaska Division of Geological and Geophysical Surveys investigated the Hill Top occurrence in the 1980s (Robinson, 1984 [RI 84-11]; Decker and others, 1995).
Indication of production None