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Mammoth (Nevada Creek)

Prospect, Inactive

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Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn
Ore minerals pyrite

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale A-1
Latitude 58.2196
Longitude -134.3305
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Mammoth prospect is at an elevation of approximately 1,000 feet on Nevada Creek, on Douglas Island. It is just south of the center of the north side of section 20, T. 42 S., R. 68 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Mammoth prospect was discovered in the 1905 and was developed by 2 adits, each with 100 to 200 feet of workings (Redman and others, 1989). The prospect was explored by Hecla Mining Company in 1990 and 1991 (Bundtzen and others, 1991; Swainbank and others, 1991). The prospect is in chlorite phyllite interbedded with lesser quartz-sericite phyllite, adjacent to a fault along Nevada Creek. Both phyllites contain 1 to 3 percent disseminated pyrite. U.S. Bureau of Mines samples contained up to 0.5 ppm gold, 9.3 ppm silver, 730 ppm copper, 3,580 ppm lead, and 860 ppm zinc (Redman and others, 1989). The deposit is similar to the Alaska Treasure Mine (JU228), Yakima (JU207), Red Diamond (JU232), and Homestake prospects (JU231), which Newberry and others (1997) interpret as Cretaceous volcanogenic massive sulfide deposits.
Southeastern Douglas Island is underlain mainly by Upper Jurassic to mid-Cretaceous, marine argillite and graywacke, interbedded with basaltic volcanic and volcaniclastic rocks (Brew and Ford, 1985). The strata are regionally metamorphosed to prehnite-pumpellyite or greenschist grade.
Geologic map unit (-134.332264627729, 58.2192700694608)
Mineral deposit model Metamorphosed Kuroko massive sulfide deposit (Cox and Singer, 1986; model 28a)
Mineral deposit model number 28a
Age of mineralization Newberry and others (1997) have interpreted this deposit as a Cretaceous volcanogenic massive sulfide deposit.
Alteration of deposit Sericite.

Production and reserves

Workings or exploration The deposit at the Mammoth prospect was discovered in the 1905 and was developed by 2 adits, each with 100 to 200 feet of workings. The prospect was explored by Hecla Mining Company in 1990 and 1991(Bundtzen and others, 1991; Swainbank and others, 1991).
Indication of production None

References

References

Brew, D.A., and Ford, A.B., 1985, Preliminary reconnaissance geologic map of the Juneau, Taku River, Atlin, and part of the Skagway 1:250,000 quadrangles, southeastern Alaska: U.S. Geological Survey Open-File Report 85-395, 23 p., 2 sheets, scale 1:250,000.
Bundtzen, T.K., Swainbank, R.C., Wood, J.E., Clough, A.H., 1991, Alaska's Mineral Industry 1991: Alaska Division of Geological & Geophysical Surveys, Special Report 46, 89 p.
Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive sulfide deposits of Alaska, in Goldfarb, R.J. and Miller, L. D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 120-150.
Redman, E.C., Maas, K.M., Kurtak, J.M., and Miller, L.D., 1991, Section D: Juneau Gold Belt subarea, in U.S. Bureau of Mines, Mineral investigations in the Juneau Mining District, Alaska, 1984-1988: Volume 2 - Detailed mine, prospect, and mineral occurrence descriptions: U.S. Bureau of Mines Special Publication VOL. 2D, 424 p., 19 sheets.
Swainbank, R.C., Bundtzen, T.K., and Wood, J.E., 1991, Alaska's mineral industry, 1990: Alaska Division of Geological and Geophysical Surveys Special Report 45, 78 p.
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 12/15/2001