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Unnamed (near Mt. Barnard)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Co
Ore minerals chalcopyrite; pyrite; pyrrhotite
Gangue minerals epidote

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale A-6
Latitude 59.09
Longitude -136.9
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

Geologic description

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.
Geologic map unit (-136.901890439915, 59.0896017112333)
Mineral deposit model Probable replacement deposit adjacent to intrusive (Cox and Singer, 1986; model 19a).
Mineral deposit model number 19a
Age of mineralization Probably Cretaceous or younger based on its association with nearby granitic intrusive rocks (Brew and others, 1978).
Alteration of deposit Chloritization, epidotization, sericitization.

Production and reserves

Indication of production None

Additional comments

There are probably similar deposits in the vicinity, but the rugged terrain and glaciers hamper investigation (Brew and others, 1978). The deposit is within Glacier Bay National Park and Preserve where exploration and development is restricted.

References

MRDS Number A013116

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.
Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001