Unnamed (north bank of the Kotsina River)

Occurrence, Inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MC
Quadrangle map, 1:63,360-scale C-8
Latitude 61.7193
Longitude -143.9204
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the north bank of the Kotsina River, 4,200 feet downstream of the mouth of Finnesand Creek. It is at an elevation of about 2,600 feet, 3,000 feet southwest of the center of section 2, T. 2 S., R 8 E. of the Copper River Meridian. This is locality 171 of MacKevett (1976) and locality 5 of MacKevett and others (1978). The location is accurate to within 100 feet. Cobb and MacKevett (1980) included this occurrence under the name 'Kotsina R.'.

Geologic setting

Geologic description

This occurrence consists of native copper, chalcocite, and some malachite and azurite associated with quartz veins and amygdule fillings in Triassic Nikolai Greeenstone (Moffit and Mertie, 1923; MacKevett, 1976). The occurrence is at a narrow part of the Kotsina River and native copper is present in greenstone on both banks (Moffit and Mertie, 1923). The widespread deposition of copper in Triassic greenstone and limestone of the area is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic or Early Cretaceous (MacKevett and others, 1997). Copper-bearing minerals were deposited in the underlying Nikolai Greenstone at about 112 Ma (Silberman and others, 1980).
Geologic map unit (-143.922494088652, 61.7188381281582)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23)
Mineral deposit model number 23
Age of mineralization Cretaceous? The widespread deposition of copper in Triassic greenstone and limestone of the area is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic or Early Cretaceous (MacKevett and others, 1997). Copper-bearing minerals were deposited in the underlying Nikolai Greenstone at about 112 Ma (Silberman and others, 1980).
Alteration of deposit Oxidation.

Production and reserves

Workings or exploration Only limited surface examination.
Indication of production None

Additional comments

The locality is in the Wrangell-Saint Elias National Park and Preserve.

References