Unnamed (southwest Gilbert Peninsula)

The Unnamed (southwest Gilbert Peninsula) is a copper and molybdenum 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: Unnamed (southwest Gilbert Peninsula)

Commodity

Primary: Copper
Primary: Molybdenum
Secondary: Zinc
Secondary: Bismuth
Secondary: Silver

Location

State: Alaska
District: Juneau

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: Porphyry Cu-Mo

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Silicification in stockwork zones.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chalcopyrite
Ore: Molybdenite
Ore: Pyrite
Ore: Sphalerite
Gangue: Quartz

Comments

Comment (Deposit): Model Name = Porphyry copper-molybdenum (Cox and Singer, 1986; model 21a).

Comment (Geology): Geologic Description = Southern Gilbert Peninsula and nearby areas are mainly underlain by granitic rock of Cretceous age containing local inliers of metamorphosed hornfels and marble of Paleozoic age (Brew and others, 1978). On the southwest tip of Gilbert Peninsula,stockworks of quartz veins in altered quartz diorite--cut by light colored aplite (alaskitic) dikes--occur in a silicified zone at least 50 feet wide and several hundred feet long. The quartz veins contain minor amounts of chalcopyrite and molybdenite close to vein selvages. The mineralogy and intrusive setting suggests a porphyry copper-molybdenum model. Pyritic stockworks and somewhat younger crosscutting pyritic veins also occur to the east across Hugh Miller Inlet and west across Scidmore Inlet. Selected vein samples from location 45 contained as much as 10 ppm silver, 7000 ppm copper and 2000 ppm molybdenum (MacKevett and others, 1971); chip samples collected across 52- and 100-foot long lines were nearly barren. Samples collected in pyritic stockwork vein areas on the west side of Scidmore Inlet contained a trace of molybdenum and as much as 70 ppm bismuth, and 1500 ppm zinc (Kimball and others, 1978, location 55).

Comment (Geology): Age = Tertiary.

Comment (Exploration): Status = Inactive

Comment (Commodity): Gangue = alteration products of quartz diorite

Comment (Commodity): Gangue = alaskite

Comment (Deposit): Other Comments = Fairly large but very low grade quartz vein and stockwork system. It is in Glacier Bay National Park and Preserve.

Comment (Reference): Primary Reference = MacKevett and others, 1971

Comment (Workings): Workings / Exploration = The mineralized area was described briefly by Rossman (1963, B 1121-K) and investigated in 1966 in conjunction with the Geological Survey's study of Glacier Bay (MacKevett and others, 1971). There are no mine workings. A 0.5 foot quartz vein collected on the southwest tip of Gilbert Peninsula contained 1000 ppm copper; a selected high-grade piece of quartz float contained 10 ppm silver, 7000 ppm copper and 2000 ppm molybdenum (MacKevett and others, 1971, p. 50-51, table 9). To the west, across Scidmore Inlet, a selected sample contained 1500 ppm zinc and 70 ppb bismuth. The average grade of exposed materials is very low, as long chip samples contained only near background amounts of valuable metals.

References

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Mount Fairweather quadrangle, AK: U.S. Geological Survey Miscellaneous Field Study Map MF-436, 1 sheet, scale 1:250,000.

Reference (Deposit): Rossman, Darwin, 1963, Geology of the eastern part of the Mount Fairweather quadrangle, Glacier Bay, Alaska: U.S. Geological Survey Bulletin 1121-K, p. K1-K57.

Reference (Deposit): Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375.

Reference (Deposit): MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.

Reference (Deposit): Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p.

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