Island Mountain

The Island Mountain is a molybdenum, zinc, copper, and gold 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: Island Mountain

Commodity

Primary: Molybdenum
Primary: Zinc
Primary: Copper
Primary: Gold
Secondary: Iron
Secondary: Arsenic

Location

State: Alaska
District: Yentna

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Not available

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Propylitic (chlorite-epidote-carbonate +/- magnetite); argillic/sericitic; silicic.

Rocks

Role: Host
Age Type: Host Rock
Age Young: Early Oligocene
Age Old: Early Cretaceous

Analytical Data

Not available

Materials

Ore: Arsenopyrite
Ore: Chalcopyrite
Ore: Gold
Ore: Molybdenite
Ore: Pyrite
Ore: Pyrrhotite
Ore: Sphalerite
Gangue: Magnetite
Gangue: Quartz

Comments

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Host rocks are late Cretaceous or Early Tertiary based on K-Ar ages published by Reed and Elliott (1970). The deposit is probably related to these intrusions.

Comment (Deposit): Model Name = Porphyry copper(?); porphyry copper-gold(?); polymetallic vein; replacement

Comment (Geology): Geologic Description = Reed and Elliott (1970) show this locality to be underlain by Mesozoic sediments (KJs) of the Kahlitna terrane that are intruded by a small body of granite and quartz monzonite (TKig). Detailed mapping in the late 1980's by Cominco American Incorporated identified veins and disseminations of pyrite-chalcopyrite and arsenopyrite-gold and stockwork quartz veins with magnetite and trace amounts of molybdenite cutting fine- to medium- grained plagioclase-hornblende porphyritic andesite and medium-grained monzonitic plutonic rocks at this site. Carbonate-rich beds in the sedimentary country rocks are locally replaced with pyrrhotite, pyrite, and sphalerite. Numerous occurrences are reported over an 8 square mile area. (Cominco American Incorporated, unpublished reports, 1987and 1988.) Host rocks are most likely Late Cretaceous or Early Tertiary(?) based on nearby K-Ar ages published by Reed and Lanphere (1972). Mineralization is probably related to these intrusions.

Comment (Reference): Primary Reference = Reed and Elliott, 1970.

Comment (Workings): Workings / Exploration = Exploration included silt sampling, mapping, rock and contour soil sampling, soil grid geochemical surveys, magnetic and VLF geophysical surveys and diamond drilling by Cominco America in mid-1980's.

Comment (Geology): Age = Host rocks are Eocene - Late Cretaceous.

References

Reference (Deposit): Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 sheets, scale 1:250,000.

Reference (Deposit): Reed, B.L., and Elliot, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 plates, scale 1:250,000.

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