Unnamed Occurrence (ARDF - SK018; near Mt. Barnard), Glacier Bay District, Juneau District, Skagway-Hoonah-Angoon Borough, Alaska, USA
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Location: This occurrence is at an elevation of 5,475 feet in Glacier Bay National Park and Preserve; it is at the top of a nunatak, 2.6 miles southeast of the summit of Mount Barnard. It is shown as location 38 on Plate III of Brew and others (1978) and location SE27 by Nokleberg and others (1987).
Geology: The following description is summarized from Brew and others (1978). Small pods up to 0.5 foot thick of pyrrhotite and pyrite with a trace of chalcopyrite are associated with andesite, greenstone, epidote, and thin bands of limestone or marble. Abundant chloritic and some sericitic alteration are in a contact metamorphic zone near a Cretaceous granitic intrusive. A grab sample of one pod contained 1,000 ppm copper, 0.1 ppm gold, 0.5 ppm silver, and 100 ppm cobalt. The mineralization is probably Cretaceous, based on the age of the granitic intrusive which is associated with it.
Age: Probably Cretaceous or younger based on its association with nearby granitic intrusive rocks (Brew and others, 1978).
Alteration: Chloritization, epidotization, sericitization.
Commodities (Major) - Cu; (Minor) - Ag, Au, Co
Development Status: None
Deposit Model: Probable replacement deposit adjacent to intrusive (Cox and Singer, 1986; model
Mineral List
4 entries listed. 4 valid minerals.
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References
Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale 1:600,000. Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p., 7 sheets. Cobb, E.H., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Skagway quadrangle, Alaska; Supplement to Open-File Report 78-316; Part A, Summaries of data to January 1, 1980: U.S. Geological Survey Open-File Report 81-82-A, 11 p. Cobb, E.H., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Skagway quadrangle, Alaska; Supplement to Open-File Report 78-316; Part B, Lists of references to January 1, 1980: U.S. Geological Survey Open-File Report 81-82-B, 10 p. Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.