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  3. Alaska Resource Data File (ARDF)

Unnamed (east of lower Nabesna Glacier)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Ore minerals azurite; malachite

Geographic location

Quadrangle map, 1:250,000-scale NB
Quadrangle map, 1:63,360-scale A-4
Latitude 62.0335
Longitude -142.8441
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the low, west-facing slopes along the east side of Nabesna Glacier. It is at an elevation of about 4,800 feet, 1,500 feet east of the glacier, and 2,800 feet south-southwest of elevation 5570. The occurrence is about 0.6 mile southeast of the center of section 16, T. 3 N., R. 14 E. of the Copper River Meridian. This is locality 18 of Richter (1973), locality 28 of Richter and others (1975), and National Park Service locality WRST-47 (unpublished data). Cobb and Richter (1980) included this locality as an 'Unnamed occurrence'. It is located to within a few hundred feet.

Geologic setting

Geologic description

This is a 30- by 200-foot zone of malachite- and azurite-stained amygdaloidal basalt (Richter and others, 1975). A composite chip sample across 50 feet of copper-stained basalt contained more than 20,000 parts per million (ppm) copper and 1.5 ppm silver (Richter and Matson, 1970 [OFR 70-276]). The basalt is part of the Triassic, Nikolai Greenstone (Richter, 1973). Copper mineralization is locally common in Nikolai Greenstone and is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic to Early Cretaceous (MacKevett and others, 1997).
Geologic map unit (-142.846223154967, 62.0330971577391)
Mineral deposit model Basaltic copper (Cox and Singer, 1986; model 23)
Mineral deposit model number 23
Age of mineralization Cretaceous? Copper mineralization is locally common in Nikolai Greenstone and is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic to Early Cretaceous (MacKevett and others, 1997).

Production and reserves

Indication of production None

Additional comments

The occurrence is in the Wrangell-St. Elias National Preserve.

References

MRDS Number A011401

References

Cobb, E.H., and Richter, D.H., 1980, Summaries of data on and list of references to metallic and selected nonmetallic mineral deposits in the Nabesna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-927, 117 p.
MacKevett, E.M., Jr., Cox, D.P., Potter, R.W., III, and Silberman, M.L., 1997, Kennecott-type deposits in the Wrangell Mountains, Alaska--High-grade copper ores near a basalt-limestone contact, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 66-89.
Richter, D.H., and Matson, N.A., Jr., 1970, Geochemical data from the Nabesna A-4 quadrangle, Alaska: U.S. Geological Survey Open-File Report 70-276, 14 p., 1 sheet, scale 1:63,360.
Richter, D.H., Singer, D.A., and Cox, D.P., 1975, Mineral resources map of the Nabesna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-655-K, 1 sheet, scale 1:250,000.
Reporters Travis L. Hudson (Applied Geology)
Last report date 11/24/2002