Lichen; Rush Prospect, Valdez Creek District, Matanuska-Susitna Borough, Alaska, USA
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Location: This prospect is at an elevation of about 3,150 feet, about 6 miles west of the Susitna River and 4.0 miles southeast of the center of Coal Lake. The prospect is about 0.15 mile west of the center of sec. 2, T. 32 N., R. 11 E., Seward Meridian. The location is accurate to within 1/4 mile. This is locality 18 of Csejtey and Miller (1978).
Geology: This prospect is a stratabound copper deposit in Triassic(?) metavolcanic rocks. Veins and disseminated sulfides occur in a mafic, volcanic flow (Smith and others, 1975; Schmidt and others, 2002). The ore minerals are confined to a single flow, and consist of disseminations and veinlets of bornite, chalcopyrite, covellite, digenite, and malachite. Veinlets average less than 0.4 inches thick and contain quartz, feldspar, and epidote as well as sulfides. The mineralized zone is about 6 feet by 3,000 feet in size; it strikes N60W and dips nearly vertically. The host rock has undergone greenschist-grade regional metamorphism and is coated with secondary iron and copper minerals. Samples of mineralized rock contain up to 4.5 percent copper, 16 parts per million gold, and 68 parts per million silver (Smith and others, 1975). The prospect was explored in the 1970's by Cities Service Minerals using soil geochemical sampling, ground magnetic and EM surveys, and excavation of 2 trenches. Seraphim Engineering and Cities Service Minerals Company staked 145 claims in 1975-1976. The Amphitheater 1-25 claims were staked by Cominco American in 1988. As of January 1, 2000 a large block of state mining claims and prospecting sites covered the prospect (Northern Associates Inc., written commun., 2001).
Workings: The prospect was explored in the 1970's by Cities Service Minerals using soil geochemical sampling, ground magnetic and EM surveys, and excavation of 2 trenches. Seraphim Engineering and Cities Service Minerals Company staked 145 claims in 1975-1976. The Amphitheater 1-25 claims were staked by Cominco American in 1988. As of January 1, 2000 a large block of state mining claims and prospecting sites covered the prospect (Northern Associates Inc., written communication, 2001).
Age: Occurs in Triassic(?) metavolcanic rocks.
Alteration: The volcanic host rock is altered to chlorite and epidote and stained with secondary iron and copper minerals.
Commodities (Major) - Ag, Au, Cu
Development Status: None
Deposit Model: Basaltic copper (Cox and Singer, 1986; model 23)
Mineral List
8 entries listed. 7 valid minerals.
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References
Cobb, E.H., and Csejtey, Bela, Jr., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Talkeetna Mountains quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-716, 63 p. Csejtey, Bela, Jr., and Miller, R.J., 1978, Map and table describing metalliferous and selected nonmetalliferous mineral deposits in the Talkeetna Mountains quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-558-B, 22 p., 1 sheet, scale 1:250,000. Csejtey, Bela, Jr., Nelson, W.H., Jones, D.L., Silberling, N.J., Dean, R.M., Morris, M.S., Lanphere, M.A., Smith, J.G., and Silberman, M.L, 1978, Reconnaissance geologic map and geochronology, Talkeetna Mountains quadrangle, northern part of Anchorage quadrangle, and southwest part of Healy quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-558-A, 60 p., 1 sheet, scale 1:250,000. Kurtak, J.M., Southworth, D.D., Balen, M.D., and Clautice, K.H., 1992, Mineral investigations in the Valdez Creek mining district, south-central Alaska: U.S. Bureau of Mines Open-File Report 1-92, 659 p., 2 plates, scale 1:250,000. MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000. Schmidt, J.M., Werdon, M.B., and Wardlaw, B., 2002 (2003), New mapping near Iron Creek, Talkeetna Mountains, indicates presence of Nikolai Greenstone, in Clautice, K.H., ed., Short Notes on Alaska geology 2003: Alaska Division of Geological and Geophysical Surveys Professional Report 120, p. 101-108. Singer, D.A., Csejtey, Bela, Jr., and Miller, R.J., 1978, Map and discussion of the metalliferous and selected non-metalliferous mineral resources of the Talkeetna Mountains quadrangle, Alaska: U.S. Geological Survey Open-file Report 78-588-Q, 33 p., 1 sheet, scale 1:250,000. Smith, T.E., Bundtzen, T.K., and Trible, T.C., 1975, Stratabound copper-gold occurrence, northern Talkeetna Mountains, Alaska: Alaska Division of Geological and Geophysical Surveys Miscellaneous Paper 3, 7 p.