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Twin Lakes East

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Ore minerals bornite; chalcopyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale LC
Quadrangle map, 1:63,360-scale C-2
Latitude 60.72
Longitude -153.7
Nearby scientific data Find additional scientific data near this location
Location and accuracy Locality is on Peak 6,515 approximately 4.8 km NE of the eastern end of Twin Lakes. This is locality 12 of Nelson and others (1985) and locality 20 of MacKevett and Holloway (1977). Sec. 8, T. 7 N., R. 25 W., of the Seward Meridian. Locality is accurate to within 1.6 km.

Geologic setting

Geologic description

Disseminated chalcopyrite, bornite, and associated pyrrhotite occur in mafic to intermediate metavolcanic rocks interbedded with marble (Nelson and others, 1985; 1983, unit Tvf). Nelson and others (1983) report small intrusive bodies that range in composition from granite to gabbro also occur in vicinity. Potassium-argon ages range from 56.2 to 62.7 m.y. (Eakins and others, 1978).
Geologic map unit (-153.702262544059, 60.7193405372519)
Mineral deposit model Kuroko massive sulfide? or Porphyry Cu, skarn related? (Cox and Singer, 1986; model 28a? or 18a?)
Mineral deposit model number 28a? or 18a?
Age of mineralization The metavolcanic rocks that host the mineralization have potassium-argon ages, by D.L. Turner, that range from 56.2 to 62.7 m.y. (Eakins and others, 1983).
Alteration of deposit Unknown

Production and reserves

Workings or exploration Unknown
Indication of production None
Reserve estimates No reserves
Production notes No production

Additional comments

Site is in Lake Clark National Park and Preserve.

References

MRDS Number A106367

References

Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part A, Summaries to January 1, 1981: U.S. Geological Survey Open-File Report 81-1343-A, 25 p.
Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part B, Lists of references to Januray 1, 1981: U.S. Geological Survey Open-File Report 81-1343-B, 20 p.
Eakins, G.R., Gilbert W.G., and Buntzen, T.K., 1978, Preliminary bedrock geology and mineral resource potential of west-central Lake Clark quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File Report 118, 15 p., 2 plates, scale 1:25,000.
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.
Nelson, W.H., King, H.D., Case, J.E., Tripp, R.B., Crim, W.D., and Cooley, E.F., 1985, Mineral resource map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-B, 1 sheet, scale 1:250,000.
Resource Associates of Alaska, Inc., 1976, Geology and geochemistry of certain land within the Lake Clark National Park: Contract report for U.S. Bureau of Mines, Contract JO166108, 7 v.
Reporters D.P. Bickerstaff (USGS)
Last report date 6/15/1998