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Fourth of July Creek

Prospect, Inactive

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Alternative names

Woodin and Herman

Commodities and mineralogy

Main commodities Cu
Ore minerals bornite; chalcopyrite; malachite

Geographic location

Quadrangle map, 1:250,000-scale MC
Quadrangle map, 1:63,360-scale C-6
Latitude 61.5238
Longitude -143.1536
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at the head of Fourth of July Creek (MacKevett, 1972). It is at an elevation of about 5,400 feet, 3,300 feet north of elevation 6012, and 1,000 feet north-northwest of the center of section 13, T. 4 S., R. 12 E. of the Copper River Meridian. This is locality 99 of MacKevett (1976); the location is accurate to within a few hundred feet.

Geologic setting

Geologic description

This deposit consists of malachite along fractures and thin seams of chalcopyrite and bornite at the contact of amygdaloidal and more massive rock in highly fractured Triassic Nikolai Greenstone (Moffit and Maddren, 1909; MacKevett, 1976). A short adit and surface pits explored this prospect. 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 (-143.155679969668, 61.5233579938139)
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 A short adit and numerous surface workings explored this prospect.
Indication of production Undetermined

Additional comments

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

References

MRDS Number A011721

References

MacKevett, E.M., Jr., 1972, Geologic map of the McCarthy C-6 quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-979, 1 sheet, scale 1:63,360.
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.
Moffit, F.H., and Maddren, A.G., 1909, Mineral resources of the Kotsina-Chitina region, Alaska: U.S. Geological Survey Bulletin 374, 103 p.
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