Unnamed (west of Slana River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Ni
Ore minerals chalcopyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.0814
Longitude -144.3707
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is on the west side of the Slana River about 3.7 miles west-northwest of Gillett Pass at an elevation of 4,200 feet. The occurrence is about 0.3 mile east of the center of section 13, T. 15 N., R. 5 E., Copper River Meridian. The occurrence corresponds to locality 5 of Richter (1967), locality 4 of Richter and others (1977), locality 31 on figure 5 of Cobb (1979 [OFR 79-238]), and locality 143 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

The rocks at this occurrence are Nikolai Greenstone of Middle or Late Triassic age (Richter and others, 1977). The rocks were previously mapped as Slana basalt (Richter (1967). The basalt is amygdaloidal and pervasively altered; phenocrysts of plagioclase, pyroxene, and olivine are altered and occur in a groundmass that has been largely altered to chlorite, epidote, and serpentinite. Minerals contained in amygdules include quartz, potassium feldspar, calcite, chlorite, epidote, pumpellyite, prehnite, and zeolite minerals (Richter and others, 1977).
The mineralized area is about one-half mile south of the Denali Fault and is cut by subsidiary faults subparallel to it (Richter and others, 1967). The occurrence consists of pyrrhotite with lesser chalcopyrite in a lenticular mass about 10 feet thick and 100 to 150 feet long enclosed in the altered basalt. The topography is very steep, and only float material was sampled. A sample of pyrrhotite-rich float contained 0.6 percent copper, 0.04 percent nickel, 0.02 ounce of gold per ton, and a trace of silver (Richter, 1967).
A stream-sediment sample collected in the gulch below the deposit contained 340 parts per million (ppm) copper, 60 ppm lead, and more than 1,000 ppm arsenic (Richter, 1967).
Geologic map unit (-144.372930992222, 63.0810117051208)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Late Triassic or younger, on the basis of the age of host rock.
Alteration of deposit Pervasive propylitic alteration of basalt.

Production and reserves

Workings or exploration The massive sulfide lens is exposed on a very steep slope and has not been mapped or sampled in detail.
Indication of production None

References