Unnamed (between Clearwater Creek and West Fork Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu
Other commodities Au
Ore minerals bornite; chalcocite; malachite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.2145
Longitude -146.8302
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 5,500 feet about midway between Clearwater Creek and the West Fork Maclaren River. The map site is near the top of the ridge about 0.4 mile west-northwest of VABM Little in section 15, T. 20 S., R. 5 E., Fairbanks Meridian. The occurrence corresponds to locality 8 in figure 4 of Cobb (1979 [OFR 79-238]) and to locality 15 in table 2 of Nokleberg and others (1991). The location is probably accurate within one-third mile.

Geologic setting

Geologic description

The country rock at this occurrence is basalt of the Nikolai Greenstone of Late Triassic age (Nokleberg and others, 1991). The mineral deposit is a vein in propylitically altered greenstone. A quartz-epidote vein in an approximately 9-foot-wide shear zone contains bornite, chalcocite, and malachite. Sample 79IL031A of vein material assayed 2.4 percent copper, 15 parts per million (ppm) silver, and 0.1 ppm gold (Nokleberg and others, 1991, locality 15).
Geologic map unit (-146.832466842746, 63.2140601842772)
Mineral deposit model Copper-bearing vein in weakly cupriferous greenstone. Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization The copper deposits are younger than a pre-Late Jurassic period of folding of basaltic host series (Stout, 1976, p. 30-31). They are probably Cretaceous or early Tertiary (see MH060).
Alteration of deposit Propylitic alteration of basalt.

Production and reserves

Workings or exploration The occurrence was probably first reported in the early 1970s (Smith and others, 1973, 1975); it was revisited and sampled by the U.S. Geological Survey in the 1980s (Nokleberg and others, 1991).
Indication of production None