Unnamed Occurrence (ARDF - SI174; west of upper Indian River), Chichagof District, Sitka Borough, Alaska, USA
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Geology: This occurrence consists of magnetite and chromite in serpentine. Loney and others (1963, 1975) map this small Mesozoic serpentinite body (sliver?) in rocks of the Jurassic and Triassic, Kelp Bay Group which consists of phyllite, greenschist, greenstone, graywacke, and semischist that has been cataclastically deformed. There is no indication that the magnetite and chromite are other than normal trace minerals in the serpentine. Spectrographic analysis indicates a small amount of nickel in the samples but probably no more than the expected level of background in serpentine.
Workings: Only surface sampling.
Age: The magnetite and chromite was probably contemporaneous with the solidification of the ultramafic rock that was altered to serpentine in the Mesozoic.
Commodities (Major) - Cr, Fe, Ni
Development Status: None
Deposit Model: Minor magnetite and chromite in serpentine.
3 entries listed. 2 valid minerals.
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Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p. Cobb, E.H., 1972, Metallic mineral resources map of the Sitka quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-467, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Sitka quadrangle: U.S. Geological Survey Open-File Report 78-450, 124 p. Loney, R.A., Berg, H.C., Pomeroy, J.S., and Brew, D.A., 1963, Reconnaissance geologic map of Chichagof Island and northwestern Baranof Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-388, 1 sheet, scale 1:250,000. Loney, R.A., Brew, D.A., Muffler, L.J.P., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p. U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]