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Unnamed (on western Nakchamik Island)

Prospect, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Pb; Zn
Ore minerals chalcopyrite; galena; pyrite; sphalerite
Gangue minerals quartz; barite

Geographic location

Quadrangle map, 1:250,000-scale SW
Quadrangle map, 1:63,360-scale B-6
Latitude 56.34
Longitude -157.88
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is on the western part of Nakchamik Island which is located approximately 10 miles south of Cape Kumliun in Chignik Bay (MacKevett and Holloway, 1977, locality 8; Cox and others, 1981, locality 5). Site location is at an elevation of about 700 feet and is accurate to within 1/2 mile.

Geologic setting

Geologic description

On Nakchamik Island, dacite plug domes intrude Oligocene and Eocene volcanic rocks of the Meshik Formation (Detterman and others, 1981). The prospect is marked by a large color anomaly. Closely-spaced quartz(?) veinlets containing abundant pyrite and chalcopyrite have been noted. Stream-sediment samples contain anomalous values in copper, lead, silver, and zinc and many contain barite. Cox and others (1981) report the grade of surface samples at <0.2 percent copper. Sixteen rock samples were collected in the 1970s by the U.S. Geological Survey (Yount and others, 1978). The highest values obtained were 1600 ppm copper, 130 ppm lead, and 260 ppm zinc.
Geologic map unit (-157.882038851139, 56.3392322501217)
Mineral deposit model Porphyry copper (Cox and Singer, 1986, model 17)
Mineral deposit model number 17
Age of mineralization Tertiary.
Alteration of deposit Country rocks are propylitically and sericitically altered. The area is marked by a large color anomaly.

Production and reserves

Workings or exploration Remnants of old mining equipment have been found at this prospect, indicating early exploration. The U.S. Geological Survey collected 16 rock samples in the 1970s (Yount and others, 1978). The highest metal values obtained were 1600 ppm copper, 130 ppm lead, and 260 ppm zinc. Cox and others (1981) report surface copper values at <0.2 percent.
Indication of production None

Additional comments

This site is on land selected by the Koniag Native Corporation.

References

MRDS Number A012446

References

Cox, D.P., Detra, D.E., and Detterman, R.L., 1981, Mineral resource maps of the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF- 1053-K, 2 sheets, scale 1:250,000.
Detterman, R.L., Miller, T.P., Yount, M.E., and Wilson, F.H.,1981, Geologic map the Chignik and Sutwik Island quadrangles Alaska: U.S. Geologic Survey Miscellaneous Investigations Series Map I-1229, 1 sheet, scale 1:250,000.
Wilson, F.H., 1980, Late Mesozoic and Cenozoic tectonics and age of porphyry copper prospects, Chignik and Sutwik Island quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 80-543, 94 p., 5 sheets, scales 1:250,000 and 1 inch = 1,000 feet.
Young, L.E., St. George, P., and Bouley, B., 1997, Porphyry copper deposits in relation to the magmatic history and palinspastic restoration of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 306-333.
Yount, M.E., Cooley, E.F., and O'Leary, R.M., 1978, Sample location map, analytical data, and statistical summary of analyses of rock samples, Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-557, 1 sheet, scale l:250,000.
Reporters S.H. Pilcher (Anchorage)
Last report date 1/31/2000