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Unnamed (west-northwest of Lower Tangle Lake)

Occurrence, Inactive

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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

References

MRDS Number A011791

References

Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p.
Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000.
Stout, J.H., 1976, Geology of the Eureka Creek area, east-central Alaska Range: Alaska Division of Geological and Geophysical Surveys Geologic Report 46, 32 p., 1 plate, scale 1:63,360.
Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 6/17/2002