Unnamed Occurrence (ARDF - SI178; east of Arrowhead Peak), Chichagof District, Sitka Borough, Alaska, USA
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Geology: This occurrence is near the contact of two similar units of Jurassic and Triassic age (Loney and others, 1975). The Khaz Formation consists of graywacke, greenschist, metachert, phyllite, and minor limestone. The Kelp Bay Group consists of quartzite, greenschist, greenstone, graywacke and semischist, all of which are subject to intense cataclasis. The occurrence consists of magnetite and chromite in serpentine, which probably are small fault blocks or slivers (Loney and others, 1963). The serpentinite body is too small to be shown on the geologic map of Loney and other (1975). There is no indication that the occurrence is any more than accessory minerals in a small serpentinite body. Samples of diabase or greenstone collected by Loney and others (1963) show small amounts of chromium, nickel, copper, cobalt, and zinc that are little if any above normal background in these types of rocks.
Workings: Only surface sampling.
Age: Triassic or younger based on the age of the rocks in the area.
Commodities (Major) - Cr, Fe
Development Status: None
Deposit Model: Accessory magnetite and chromite in serpentine.
3 entries listed. 2 valid minerals.
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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.