Unnamed Occurrence (ARDF - SW001; on Cape Kumlik), Alaska Peninsula District, Lake and Peninsula Borough, Alaska, USA
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Location: This occurrence is located on the east coast of the mainland between Kujulik and Aniakchak Bays. The map site is about 1 mile inland from the easternmost tip of Cape Kumlik (MacKevett and Holloway, 1977, localities 3 and 7; Cox and others, 1981, locality 1). The site location is accurate to within 1/2 mile.
Geology: At this site a quartz diorite stock has intruded volcanic rocks of the Oligocene and Eocene Meshik Formation (Detterman and others, 1981). The occurrence is marked by a large color anomaly covering about 1 section. Chalcopyrite and pyrite occur in quartz(?) veinlets and as disseminations in both the intrusive and in the surrounding volcanic rocks (Hedderly-Smith, 1977). Barite has been noted in many stream-sediment samples. Numerous rock-chip samples collected by Bear Creek Mining Company returned copper values in the 400 ppm to 1000 ppm range and several contained 1000 ppm to 2000 ppm copper (Hedderly-Smith, 1977). The highest value was 5600 ppm copper from a sample of the mineralized intrusive. Molybdenum and silver were indicated as low-order anomalies. Gold was detected in the 0.07ppm 0.31 ppm range. The higher gold values generally coincided with the higher copper values. Of 7 rock samples collected here in 1978 by the U.S. Geological Survey, only 1 contained strongly anomalous values in copper (2200 ppm) (Yount and others, 1978). Cox and others (1981) estimate a small tonnage of low grade mineralization. The rocks at the center of the mineralized area exhibit potassic alteration (Hedderly-Smith, 1977). Quartz-sericite alteration and silicification occur to the east, south, and west of the central area in both intrusive and volcanic rocks. An outer zone of propylitization is present.
Workings: Resource Associates of Alaska did a stream-sediment geochemical survey in 1975 (Hedderly-Smith, 1977). Bear Creek Mining Company geochemically sampled and mapped the occurrence in 1977 (Hedderly-Smith, 1977). Most samples returned copper values in the 400 to 1000 ppm range. One sample of mineralized intrusive contained 5600 ppm copper. Low order molybdenum and silver anomalies were also detected. The U.S. Geological Survey (Yount and others, 1978) took 7 samples in 1978. The highest copper value obtained was 2200 ppm.
Age: Tertiary.
Alteration: The rocks exhibit a zoned alteration pattern, with a central potassic core grading outward to quartz-sericite and silicification, and to peripheral propylitization.
Reserves: This occurrence is estimated to have a small tonnage of low grade (Cox and others, 1981).
Commodities (Major) - Cu; (Minor) - Ag, Au, Mo
Development Status: None
Deposit Model: Porphyry copper (Cox and Singer, 1986, model 17)
Mineral List
5 entries listed. 5 valid minerals.
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References
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. Detterman, R.L., Miller, T.P., Yount, M.E., and Wilson, F.H.,1981, Geologic map the Chignik and Sutwik Island quadrangles Alaska: U.S. Geologic Survey Miscellaneous Investigations Series Map I-1229, 1 sheet, scale 1:250,000. Hedderly-Smith, D.A., 1977 Annual report, Alaska search, Koniag Inc. region: Bear Creek Mining Company, Spokane Office, 23 p. (Report held by Kennecott Alaska, Anchorage). MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000. Yount, M.E., Cooley, E.F., and O'Leary, R.M., 1978, Sample location map, analytical data, and statistical summary of analyses of rock samples, Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-557, l sheet, scale l:250,000.
