Windy Bay Occurrence, Alaska Peninsula District, Lake and Peninsula Borough, Alaska, USA
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Location: This site is approximately 2 miles west of the head of the north arm of Windy Bay and includes the headwaters of streams draining into that head of the bay (Cox and others, 1981, locality 9). The site is accurate as plotted.
Geology: The geologic setting at this site consists of a quartz diorite stock which has intruded sedimentary units of the Jurassic Naknek Formation (Fields, 1977). These units include grits, graywacke, siliceous siltstone, and black shale. A discontinuous color anomaly is present along the inferred contact zone (Fields, 1977). The sediments near the contact have been hornfelsed and contain pyrrhotite, pyrite, rare chalcopyrite, and magnetite as disseminations and as veinlet and fracture fillings. Total sulfide content is 1-5 percent. Sulfides occur up to 1000 feet from the contact. The sulfide content of the intrusive is 1 percent or less. Chalcopyrite is present on fracture surfaces and in quartz-chlorite and pyrite veinlets. These strike approximately N 25 W and cover an area of 1000 by 4000 feet. Samples of the mineralized intrusive contained up to 424 ppm copper, 0.13 ppm gold, 32 ppm lead, 25 ppm molybdenum, and 9 ppm zinc (Fields, 1977). The intrusive exhibits local chloritization along with scattered patches of epidote and secondary biotite. The hornfelsed sediments have been silicified and contain secondary biotite and minor chlorite.
Workings: Bear Creek Mining Company briefly explored this site during the period 1975-1976. The few samples collected contained up to 424 ppm copper, 0.13 ppm gold, 32 ppm lead, 25 ppm molybdenite, and 9 ppm zinc (Fields, 1977). Resource Associates of Alaska briefly sampled this occurrence in 1979 (Anderson and others, 1979).
Alteration: Alteration in the intrusive consists of local zones containing chlorite, epidote, and secondary biotite. The sediments near the intrusive contact have been hornfelsed, silicified, and contain chlorite and secondary biotite.
Commodities (Major) - Cu, Mo; (Minor) - Au, Pb, Zn
Development Status: None
Deposit Model: Porphyry copper; porphyry copper-gold; porphyry copper-molybdenum (Cox and Sing
9 entries listed. 8 valid minerals.
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Anderson, G.D., Fitch, G.M., Lappie, D.W., Lindberg, P.A., and Fankhauser, R.E., 1979, Exploration and evaluation of Bristol Bay Native Corporation Lands, Vol. II, Book 1: Prepared for Houston Oil and Minerals Company by Resource Associates of Alaska, 78 p. (Report held by Alaska Earth Sciences, Inc., Anchorage, Alaska.) 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. Fields, E.D., 1977, 1976 Annual report: Alaska search, Chignik area-Bristol Bay region: Bear Creek Mining Company, 44 p., 22 map sheets. (Report held by the Aleut Corporation, Anchorage, Alaska.)