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Unnamed (north wall of Shiels Glacier)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au
Ore minerals galena; pyrite; pyrrhotite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-3
Latitude 60.88
Longitude -144.76
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence site is at an elevation of 2700 feet on the north wall of Shiels Glacier. It is in the SE1/4 sec. 30, T. 11 S., R. 4 E., of the Copper River Meridian. The location of the site is accurate to within 2000 ft. The occurrence is shown as site C-12 in Jansons and others (1984).

Geologic setting

Geologic description

The country rocks at this occurrence are metavolcanic rocks (greenstone) and metasedimentary rocks of the Upper Cretaceous Valdez Group. These rocks are part of a 65-mile-long belt of volcanic rocks having potential for volcanogenic massive sulfide deposits, extending to the Copper River (Nelson and others, 1984; 1985). The metavolcanic rocks contain disseminations and lenses of pyrite and pyrrhotite, and disseminations of galena and sphalerite. Two grab samples from talus contained 0.03 ppm and 5.0 ppm Au, 34 ppm and 0.92% Zn, 47 ppm and 0.20% Pb, and 5.4 ppm and 11.2 ppm Ag (Jansons and others, 1984). Pan-concentrate samples from the area contained 1000 ppm Au, 1000 ppm Ag, 1% As, and 3000 ppm Pb (Goldfarb and others, 1984). Kodosky and Teller (1989) report that the average gold value for pan-concentrate samples in this drainage is 5791 ppb. The average assays of two rock samples are 858 ppb and 1348 ppb Au, and 1750 ppm and 1038 ppm Pb.
Geologic map unit (-144.762015831081, 60.8795027657989)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a) and/or Chugach-type low-sulfide gold-quartz veins (Bliss, 1992; model 36a.1).
Mineral deposit model number 24a and/or 36a.1
Age of mineralization Late Cretaceous based on the age of the host rocks.

Production and reserves

Workings or exploration Site was sampled as part of a U.S. Bureau of Mines and U.S.G.S. mineral resource assessment of the Chugach National Forest (Jansons and others, 1984; Nelson and others, 1984). Site was also examined by private industry in 1988 (Kodosky and Teller,1989). Kodosky and Teller (1989) concluded that the drainage area had a very high probability of containing a gold-bearing quartz system. Their average gold value for pan-concentrate samples in this drainage is 5791 ppb. The average assays of two rock samples are 858 ppb and 1348 ppb Au, and 1750 ppm and 1038 ppm Pb.
Indication of production None

Additional comments

Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.

References

MRDS Number 10307387

References

Goldfarb, R.J., Nelson, S.W., Dumoulin, J.D., Miller, M.L., Hoffman, J.D., Trip, R.B., Smaglik, Suzanne, and Folger, Peter, 1984, Data report and statistical summary for samples of moraine and stream-sediment, nonmagnetic, heavy-mineral concentrates, and rock samples from the Chugach National Forest, Alaska: U.S. Geological Survey Open-File Report 84-355, 446 p. (unnumbered tables), 2 sheets, scale 1:250,000.
Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, southcentral Alaska: U.S. Bureau of Mines Mineral Land Assessment 5-84, 218 p., 2 sheets, scale 1:250,000.
Kodosky, Larry, and Teller, Steve, 1989, Economic mineral assessment of Chugach Alaska Corporation properties and selected land in the Copper, Bremner, and Tasnuna River area: Unpublished report prepared for Chugach Alaska Corporation, Anchorage, Alaska, 116 p.
Nelson, S.W., Dumoulin, J. A., and Miller, M.L., 1985, Geologic map of the Chugach National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1645-B, 16 p., 1 sheet, scale 1:250,000.
Nelson, S.W., Miller, M.L., Barnes, D.F., Dumoulin, J.A., Goldfarb, R.J., Koski, R.A., Mull, C.G., Pickthorn, W.J., Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral resource potential of the Chugach National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1645-A, 24 p., 1 plate, scale 1:250,000.
Reporters S.W. Nelson, Anchorage, AK
Last report date 6/10/2000