Unnamed (west of upper Brown Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Fe
Other commodities Ag; Cu; Sb
Ore minerals pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-2
Latitude 62.93035
Longitude -156.81769
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 2,400 feet on a knob near the head of Brown Creek. It is about 0.4 mile north-northwest of hill 2665 in the SW1/4, section 23, T. 33N., R. 40W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence consists of a pod of pyrrhotite in dense hornfels, about 650 feet from the east contact of the Cretaceous, Beaver Mountains pluton. The pod is poorly exposed. From rubble scattered across the hillside, the pod is is estimated to be 6 feet thick and 90 feet long. Two grab samples contained an average of about 20 percent iron, 1.0 parts per million (ppm) silver, 200 ppm copper, and 40 ppm antimony (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005).
Geologic map unit (-156.820049369061, 62.9297041851441)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Probably related to the Beaver Mountains pluton which has been dated at 70.1 Ma. (Bundtzen and Laird, 1982).
Alteration of deposit In hornfels near contact of granitic pluton.

Production and reserves

Workings or exploration The occurrence was mapped and sampled by the Alaska Division of Geological and Geophysical Surveys in 1979 (Bundtzen and Laird, 1982).
Indication of production None