Unnamed (west-northwest of Lower Tangle Lake)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Ore minerals bornite; chalcopyrite; malachite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-4
Latitude 63.1468
Longitude -145.9979
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is at an elevation of 4,100 feet in a small cirque west-northwest of Lower Tangle Lake. It is in the SE1/4SW1/4 section 27, T. 20 S., R. 9 E., Fairbanks Meridian. This location corresponds to locality S75 in table 2 of Nokleberg and others (1991), locality 9 of Cobb (1979 [OFR 79-238]), and an occurrence described by Stout (1976, p. 30 and plate 1).

Geologic setting

Geologic description

This occurrence includes two types of deposits. One consists of pods as much as a foot thick of massive chalcopyrite and bornite in metabasalt of Nikolai Greenstone of Late Triassic age (Stout, 1976). The other consists of chalcopyrite, bornite, and copper oxide-bearing quartz veins in north-northeast-striking joints in the greenstone. Malachite-coated copper nuggets occur in stream gravels in a nearby cirque.
The quartz veins are localized in north-northeast-trending joints that cut across the folded limbs of the Amphitheater syncline. The veins post-date late Jurassic deformation and are probably either Cretaceous related to regional metamorphism and granitic plutonism (Nokleberg and others, 1986) or early Tertiary (Stout, 1976).
Geologic map unit (-146.000145685583, 63.1463762323776)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Late Triassic and Cretaceous.

Production and reserves

Indication of production None