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  3. Alaska Resource Data File (ARDF)

Unnamed (near Contact Gulch)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Mo
Ore minerals bornite

Geographic location

Quadrangle map, 1:250,000-scale MC
Quadrangle map, 1:63,360-scale C-4
Latitude 61.5032
Longitude -142.3075
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on a bluff east of lower Contact Gulch. It is at an elevation of about 4,900 feet, 1,500 feet south of the center of section 22, T. 4 S., R 17 E. of the Copper River Meridian. This is locality 84 of MacKevett (1976); the location is accurate to within about 1,000 feet.

Geologic setting

Geologic description

This occurrence consists of bornite-bearing veins to 6 centimeters thick that occur in a 2-meter-wide fault zone that cuts Triassic Nikolai Greenstone (MacKevett, 1976). A sample of the mineralization contained 200 parts per million (ppm) silver, more than 20,000 ppm copper, and 7 ppm molybdenum. 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 (-142.309567646745, 61.5027848825381)
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).

Production and reserves

Workings or exploration Limited surface sampling.
Indication of production None

Additional comments

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

References

References

MacKevett, E.M., Jr., 1976, Mineral deposits and occurrences in the McCarthy quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-773-B, 2 sheets, scale 1:250,000.
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.
Silberman, M.L., MacKevett, E.M., Jr., Connor, C.L., and Mathews, A., 1980, Metallogenic and tectonic significance of oxygen isotope data and whole-rock potassium-argon ages of Nikolai Greenstone, McCarthy quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-2019, 31 p.
Reporters Travis L. Hudson (Applied Geology, Inc.)
Last report date 1/12/2003