Bear Mountain

Site Name

Primary: Bear Mountain

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Commodity

Primary: Molybdenum
Primary: Tungsten
Primary: Lead

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Location

State: Alaska
District: Sheenjek

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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: Occurrence
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: Core of sericitic and argillic alteration with outer zone of silicification; local peripheral areas of pyritic and propylitic alteration.

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Rocks

Name: Metasedimentary Rock
Role: Associated
Age Type: Associated Rock
Age Young: Mississippian

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Analytical Data

Not available

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Materials

Ore: Galena
Ore: Molybdenite
Ore: Wolframite
Gangue: Rutile
Gangue: Quartz
Gangue: Muscovite
Gangue: Magnetite
Gangue: Limonite
Gangue: Kaolinite
Gangue: Jarosite
Gangue: Hematite
Gangue: Goethite
Gangue: Topaz

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Comments

Comment (Geology): Geologic Description = Tungsten-rich porphyry molybdenum occurrence. Area of about 1 sq km underlain by altered complex of rhyolite porphyry, quartz porphyry, and a pipe-shaped core of intrusive breccia about 300 m in diameter; complex is cut by dikes of rhyolite porphyry and aplite. Mineralized area defined by Mo-rich gossan zone trending NW for 1.5 km over 40 ha area characterized by soil samples containing 600 ppm Mo or greater; nearly coincident with 30 ha area of soil samples containing 500 ppm W or greater. Total area of Mo + W mineralization about 50 ha; vertical and horizontal zonation evident. Central Mo-rich gossan zone, outer zone of wolframite-topaz mineralization in a Fe-enriched upper-level phase of the complex below a silicified cap, and peripheral zone of Pb-enrichment. Sulfides have largely been oxidized to limonite, hematite, goethite, jarosite, and secondary ferromolybdates; wolframite occurs as disseminated grains in porphyritic rock, quartz veins, and silicified gossan. Molybdenite and galena have each been noted in only one locality. Tertiary rhyolite porphyry stock intrudes Mississippian and older metasedimentary rocks (Barker, 1981, p. 33-40, 106-137).

Comment (Commodity): Ore Material = Unidentified secondary ferromolybdate mineral

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = Barker (1981)

Comment (Deposit): Other Comments = Part of regional E-W trend of small domes, intrusions and doubly-plunging anticlines.

Comment (Commodity): Ore Material = Unidentified secondary ferromolybdate mineral

Comment (Workings): Workings / Exploration = Rock samples taken in 1983 contain 0.1-0.8% M, 0.06-0.6% W, 2.2% F, 60-120 PPM Nb as reported in Barker and Swainbank (1985); soil sample 2521 on p. 141 of Barker (1981) from area of intrusive breccia contains 4900 ppm Mo, 860 ppm W, 400 ppm Pb and 9.7 ppm U (Barker, 1981, p. 140-150).

Comment (Commodity): Gangue = K-feldspar

Comment (Deposit): Model Name = Lode; Mo-W porphyry breccia

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References

Reference (Deposit): Cobb, E.H., Mayfield, C.F., and Brosge, W.P., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in eleven quadrangles in northern Alaska (Arctic, Baird Mountains, Chandler Lake, DeLong Mountains, Demarcation Point, Howard Pass, Misheguk Mountain, Mount Michelson, Noatak, Point Lay, and Table Mountain); Supplement to Open-File Report 75-628; Part A, Summaries of data to January 1, 1981: U.S. Geological Survey Open-File Report 81-767-A, 25 p.

Reference (Deposit): Barker, J.C., 1978, Mineral Investigations of certain lands in the eastern Brooks Range: a summary report: US Bureau of Mines Open-File No. 63-78

Reference (Deposit): Grybeck, D.J., 1977, Known mineral deposits of the Brooks Range, Alaska: US Geological Survey Open-File Report 77-166C, 41 p., 1 sheet, scale 1:1,000,000.

Reference (Deposit): Barker, J.C., and Swainbank, R.C., 1986, A tungsten-rich porphyry molybdenum occurrence at Bear Mountain, northeast Alaska: Economic Geology vol. 81, p. 1753-9

Reference (Deposit): Brosge', W.P., and Reiser, H.N., 1976, Preliminary geologic and mineral resource maps (excluding petroleum), Arctic National Wildlife Range, Alaska: U.S. Geological Survey Open-File Report 76-539, 4 sheets, scale 1:500,000.

Reference (Deposit): Brosgi, W.R., and Reiser, H.N., 1968, Geochemical maps of granitic rocks, Coleen and Table Mountain quadrangles, Alaska: U.S. Geological Survey Open-File Report 323, scale 1:250,000.

Reference (Deposit): Cobb, E.H., 1973, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 p.

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