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  3. Alaska Resource Data File (ARDF)

Unnamed (coast south of Kwain Bay)

Occurrence, Undetermined

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Commodities and mineralogy

Main commodities Fe
Other commodities Co; Mo
Ore minerals magnetite

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.067
Longitude -131.351
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents two occurrences at sea level on the southeast coast of Annette Island, about 1.5 miles south of the mouth of Kwain Bay. The occurrences are about 0.1 mile apart, in section 35, T. 78 S., R. 93 E., of the Copper River Meridian. The map site is approximately midway between the occurrences. The site corresponds to loc. 6 in Berg (1972 [I 684]), and loc. 38a, b in Karl (1992). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site are undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks; and Silurian trondhjemite that intrudes the Silurian and Ordovician rocks (Berg, 1972, Berg and others, 1988). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.
The occurrences consist of veinlets and disseminations of magnetite in shear zones in sericitized granitic rocks and schist. A sample of altered granitic rock contained 150 ppm Co and 20 ppm Mo (Karl, 1992, loc. 38a, b).
Geologic map unit (-131.352680652414, 55.0666620847203)
Mineral deposit model Disseminated magnetite mineralization of undetermined origin.
Age of mineralization Probably Late Cretaceous or younger.
Alteration of deposit Sericitization of sheared granitic rocks.

Production and reserves

Workings or exploration A sample of altered granitic rock contained 150 ppm Co and 20 ppm Mo (Karl, 1992, loc. 38a, b).
Indication of production None

References

MRDS Number 10307698

References

Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360.
Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000.
Reporters H.C. Berg, USGS
Last report date 7/7/1999