Eagle Bluff Prospect, Eagle District, Southeast Fairbanks Borough, Alaska, USA
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Geology: Eagle Bluff consists mainly of greenstone on the south and east faces; argillite crops out on the north face (Clark and Foster, 1971). The greenstone and argillite are probably equivalent to units of the Proterozoic Tindir Group; possibly the argillite is equivalent to the Adams Argillite, which is of Early Cambrian age (Foster, 1976). Limestone also crops out on Eagle Bluff, and argillite crops out for several miles from Eagle Bluff on the opposite bank of the Yukon River. The main trace of the Tintina Fault runs along the southwest side of Eagle Bluff; strands of the fault run through the bluff (Foster, 1976). Copper minerals at Eagle Bluff include chalcopyrite, malachite, and azurite (Saunders, 1953). Chalcopyrite occurs in veins with quartz and calcite, as disseminated grains in limestone, and in amygdules in greenstone. Rock samples contain as much as 3.47 percent copper. Small patches of nickel and cobalt bloom are found in a shear zone located about 1 mile southeast of Eagle Bluff on the north side of the Yukon River, as well as on Eagle Bluff about 2 miles northwest of the Yukon River (Saunders, 1953). Several samples of sulfide ore encrusted with cobalt bloom were reportedly collected from a gold- and nickel-bearing vein on Eagle Bluff by a prospector. A variety of rock types from Eagle Bluff contain locally high but sporadic concentrations of copper (more than 10,000 ppm), lead (as much as 1,500 ppm), zinc (as much as 1,500 ppm), cobalt (as much as 2,000 ppm), silver (as much as 1.5 ppm), and tin (as much as 500 ppm) (Clark and Foster, 1971). Eagle Bluff was visited by Wedow (1954) in 1948 in a reconnaissance for radioactive deposits in the Eagle-Nation area; he took samples but none was radioactive. Mining claims in the Eagle area were examined by Saunders (1954) in 1952. Clark and Foster (1971) conducted a geochemical and geological reconaissance in the Seventymile River area in 1968.
Workings: Eagle Bluff was visited by Wedow (1954) in 1948, in a reconnaissance for radioactive deposits in the Eagle-Nation area; he took samples, but none was no radioactive. Mining claims in the Eagle area were examined by Saunders (1954) in 1952. Clark and Foster (1971) conducted a geochemical and geological reconaissance in the Seventymile River area in 1968.
Commodities (Major) - Cu; (Minor) - Ag, Au, Co, Ni, Pb, Sn, Zn
Development Status: None
5 entries listed. 5 valid minerals.
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Clark, S.H.B., and Foster, H.L., 1971, Geochemical and geological reconnaissance in the Seventymile River area, Alaska: U.S. Geological Survey Bulletin 1315, 21 p. Cobb, E.H., 1977, Summary of references to mineral occurrences in the Eagle quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-845, 122 p. Eberlein, G.D., Chapman, R.M., Foster, H.L., and Gassaway, J.S., 1977, Map and table describing known metalliferous and selected nonmetalliferous mineral deposits in central Alaska: U.S. Geological Survey Open-File Report 77-168-D, 132 p., 1 sheet, scale 1:1,000,000. Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series, Map 922, 1 sheet, scale 1:250,000. Saunders, R.H., 1953, Report on the preliminary examination of the Fred J. Jenkins property near Eagle, Alaska: Alaska Territorial Department of Mines Property Examination PE 60-3, 14 p. Wedow, Helmuth, Jr., 1954, Reconnaissance for radioactive deposits in the Eagle-Nation area, east-central Alaska, 1948: U.S. Geological Survey Circular 316, 9 p.