Sheep Mountain

Site Name

Primary: Sheep Mountain

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Commodity

Primary: Gypsum-Anhydrite
Primary: Copper
Primary: Clay
Secondary: Gold

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Location

State: Alaska
District: Willow Creek

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Not available

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Large area of south flank of Sheep Mountain is strained dark red from oxidation of pyrite in greenstone (Berg and Cobb, 1967). Oxidation of Cu minerals.

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Rocks

Role: Host
Age Type: Host Rock
Age Young: Early Jurassic

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Analytical Data

Not available

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Materials

Ore: Azurite
Ore: Pyrite
Ore: Malachite
Ore: Kaolin
Ore: Gypsum
Ore: Chalcopyrite
Ore: Chalcocite
Ore: Bornite
Gangue: Calcite
Gangue: Epidote
Gangue: Quartz
Gangue: Sericite
Gangue: Serpentine

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Comments

Comment (Reserve-Resource): Reserves = the six deposits indicated and inferred reserves contain about 659,000 short tons of gypsum material (Eckhart, 1953).

Comment (Geology): Geologic Description = Early Jurassic greenstone and minor interbedded sandstone and shale is intruded by numerous mafic dikes and at least one body of unmineralized Jurassic granite. Greenstone has been hydrothermally altered and contains at least 6 separate gypsiferous deposits in altered zones along joints and shear zones. Deposits composed of pods and stringers of gypsum, quartz, alunite, kaolin minerals, pyrite and serpentine minerals (Eckhart, 1953). The gypsum-bearing material averages 25 to 30 percent gypsum, with a maximum of 50 percent. ? In addition also reported from same general area are: (1) small irregular quartz-calcite-epidote veins in greenstone containing chalcopyrite, malachite, azurite and possibly bornite and chalcocite (Berg and Cobb, 1967); (2) disseminated chalcopyrite in greenstone over 5 ft thick zone subparallel to bedding (Martin and Mertie, 1914); (3) trace gold in samples of pyritic greenstone (Berg and Cobb, 1967); and (4) minor anomalous concentrations of copper and gold associated with some of the alteration zones and nearby veins (MacKevett and Holloway, 1977).

Comment (Geology): Age = Host rock is Early Jurassic.

Comment (Production): Production Notes = About 50 tons of gypsum had been mined (Eckhart, 1953). In addition, about 55 tons of clay was mined for the manufacture of fire brick and boiler lining.

Comment (Reference): Primary Reference = Eckhart, 1953

Comment (Workings): Workings / Exploration = The gypsiferous material averages 25 to 30 percent gypsum, with a maximum of 50 percent. The six deposits indicated and inferred reserves contain about 659,000 short tons of gypsum material, of which about 50 tons of this material had been mined (Eckhart, 1953). In addition, about 55 tons of clay was mined for the manufacture of fire brick and boiler lining. Samples of pyritic greenstone assayed trace gold (Berg and Cobb, 1967), and nearby veins in alteration zones show concentrations of copper and gold (MacKevett and Holloway, 1977).

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Jurassic or younger; mineralization hosted by an Early Jurassic greenstone.

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References

Reference (Deposit): Brooks, A.H., 1915, Mineral resources of Alaska in 1914: U.S. Geological Survey Bulletin 622, 238 p.

Reference (Deposit): Eckhart, R.A., 1953, Gypsiferous deposits on Sheep Mountain, Alaska: U.S. Geological Survey Bulletin 989-B, p. 39-61.

Reference (Deposit): Rutledge, F.A., Thorne, R.L., Kerns, W.H., and Mulligan, J.J., 1953, Preliminary report: Nonmetallic deposits accessible to the Alaska Railroad as a possible source of raw materials for the construction industry: U.S. Bureau of Mines Report of Investigations 4932, 129 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Anchorage quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-409, 1 sheet, scale 1:250,000.

Reference (Deposit): Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials in the Anchorage quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-1095, 184 p.

Reference (Deposit): Capps, S.R., 1927, Geology of the upper Matanuska Valley, Alaska, with a section on the igneous rocks by J.B. Mertie, Jr.: U.S. Geological Survey Bulletin 791, 92 p.

Reference (Deposit): Brooks, A.H., 1913, Mineral resources of Alaska, report on progress of investigations in 1912: U.S. Geological Survey Bulletin 542, 308 p.

Reference (Deposit): 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.

Reference (Deposit): 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.

Reference (Deposit): Jasper, M.W., 1965, Geochemical investigations of selected areas in southcentral Alaska, 1964: Alaska Division of Mines and Minerals Geochemical Report 4, 31 p.

Reference (Deposit): Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

Reference (Deposit): Martin G.C., and Mertie, J.B., 1914, Mineral resources of the upper Matanuska and Nelchina valleys, Alaska: U.S. Geological Survey Bulletin 592-H, p. 273-299, map.

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