West Twin Peak

The West Twin Peak is a chromium mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: West Twin Peak
Secondary: West Ridge
Secondary: Eklutna Creek

Commodity

Primary: Chromium

Location

State: Alaska
District: Anchorage

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Alaskan Cr-Pt (PGE)
Model Name: Podiform chromite (minor)

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Slight serpentinization of olivine.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chromite

Comments

Comment (Reference): Primary Reference = Rose, 1966

Comment (Workings): Workings / Exploration = Chip samples across a 10 ft zone contained 7.93 percent chromite, with a Cr:Fe ratio of 2:1 (Rose, 1966). Pieces of float containing about 90 percent chromite as large as 4 inches in diameter are found on site.

Comment (Geology): Geologic Description = Chromite-rich dunite of the Jurassic Eklutna Sequence containing bands of chromite up to 1 inch thick found in a zone 10 ft thick. Chromite-rich rock could be traced for about 30 ft before it was covered by talus. Chip samples across a 10 ft zone contained 7.93 percent chromite (Rose, 1966).

Comment (Deposit): Other Comments = Unconfirmed report of the presence of tin ore (Brooks, 1918). Some confusion exists about the name of this locality. Cobb (1972, loc. 41) refers to it as Eklutna Creek, while others refer to it as West Twin Peak.

Comment (Deposit): Model Name = Podiform chromite or Alaskan PGE (Cox and Singer, 1986; models 8a or 9)

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Lower to Middle Jurassic

References

Reference (Deposit): Clark, S.H.B., and Bartsch, S.R., 1971, Reconnaissance geologic map and geochemical analyses of stream sediment and rock samples of the Anchorage B-6 quadrangle, Alaska: U.S. Geological Survey Open-File Report 475, 63 p., 2 sheets, scale 1:36,360.

Reference (Deposit): Clark, S.H.B., 1972, Reconnaissance bedrock geologic map of the Chugach Mountains near Anchorage, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map 350, 1 sheet, scale 1:250,000.

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): Rose, A.W., 1966, Geology and chromite-bearing ultramafic rocks near Eklutna, Anchorage quadrangle, Alaska: Alaska Division of Mines and Minerals Geologic Report 18, 25 p., 1 sheet, scale 1:42,000.

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): 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): Brooks, A.H., 1918, Mineral resources of Alaska, 1916: U.S. Geological Survey Bulletin 662, 469 p.

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