Unnamed (tributary to Pass Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Ore minerals chalcocite; malachite; native copper
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.1488
Longitude -146.998
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at about 4,100 feet elevation in a north-flowing tributary of Pass Creek, about a mile southwest of its junction with Clearwater Creek and in the SW1/4SW1/4 section 28, T. 20 S., R. 4 E., Fairbanks Meridian. The occurrence corresponds to locality A40 of Kurtak and others (1992), location 1 in figure 4 of Cobb (1979 [OFR 79-238]) and locality 1 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

The rocks at this occurrence are propylitized metabasalt of the Nikolai Greenstone of Late Triassic age. The metabasalt is sheared and locally silicified (Nokleberg and others, 1991; Kurtak and others, 1992). The deposit consists of copper minerals in bedrock and in float. Malachite, chalcocite, and possibly native copper occur in quartz or quartz-epidote veins and vesicles (Kurtak and others, 1992; Smith and others, 1973). U.S. Bureau of Mines sample 1416 assayed 0.16 percent copper and near background concentrations of gold (10 parts per billion) and silver (0.5 part per million) (Kurtak and others, 1992, table A41).
Geologic map unit (-147.000260902515, 63.1483558121234)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986, model 23).
Mineral deposit model number 23
Age of mineralization The deposit is probably either Cretaceous or early Tertiary (see MH060 and MH100).
Alteration of deposit Metabasalt is propylitized and locally silicified.

Production and reserves

Workings or exploration The site has low development potential for copper deposits (Kurtak and others, 1992); there are no workings of significance.
Indication of production None