Hill Occurrences, Chicagof District, Sitka Borough, Alaska, USA
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Location: These occurrences are in small bodies of pyroxenite and dunite exposed in the mountains south of the headwaters of the Vodopad River. The occurrences are about 1.6 miles west-northwest of peak 2469 and near the center of section 13, T. 57 S., R. 66 E.
Geology: Dunite and pyroxenite occur in a series of sub-parallel, northwest-trending lenses less than a mile long in a heterogeneous Triassic unit of phyllite with some quartzite, greenstone, graywacke, semischist, and metachert (Loney and others, 1975). The dunite contains thin trains and disseminations of chromite; the pyroxenite contains sparsely disseminated chalcopyrite, pyrite, and pyrrhotite. The deposit was found in 1935; claims were soon staked but were abandoned by 1942 (Guild and Balsley, 1942). Bittenbender and others (1999) collected samples of the pyroxenite for analysis. They contained 12 to 3,050 parts per million (ppm) copper and 7 to 1,100 ppm nickel. One sample, the one with the highest copper value, contained 55 parts per billion (ppb) platinum and 68 ppb palladium; all the other samples contained 5 ppb or less platinum and 10 ppb or less palladium. All the studies of the deposit indicate that the economic potential of the prospect is low (Guild and Balsley, 1942; Kennedy and Walton, 1946; Bittenbender and others, 1999).
Workings: Claims were staked in 1935 or shortly thereafter but were abandoned by 1942. There is no indication of significant workings.
Age: Loney and others (1975) indicate that the ultramafic bodies that contain the economic elements of interest are Mesozoic in age.
Commodities (Major) - Cr, Cu, Ni, Pd, Pt
Development Status: None
Deposit Model: Dunite and pyroxenite with low values of Cu, Cr, Ni, Pd, and Pt.
4 entries listed. 4 valid minerals.
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Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p. 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 Port Alexander quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-464, 1 sheet, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Port Alexander quadrangle: U.S. Geological Survey Open-File Report 78-787, 33 p. Guild, P.W., and Balsley, J.R., Jr., 1942, Chromite deposits of Red Bluff Bay and vicinity, Baranof Island, Alaska: U.S. Geological Survey Bulletin 936-G, p. 171-187. Kennedy, G.C., and Walton, M.S., Jr., 1946, Geology and associated mineral deposits of some ultrabasic rock bodies in southeastern Alaska: U.S. Geological Survey Bulletin 947-D, p. 65-84. Loney, R.A., Brew, D.A., Muffler, L.J. B., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p.