Unnamed (west arm of Dundas Bay)

The Unnamed (west arm of Dundas Bay) is a copper 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 (west arm of Dundas Bay)

Commodity

Primary: Copper
Secondary: Silver
Secondary: Cobalt

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

Not available

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chalcopyrite

Comments

Comment (Deposit): Other Comments = the copper and cobalt content of the occurrence is significant , but the size is limited because the dikes are narrow and the island small. The site is in Glacier Bay National Park and Preserve.

Comment (Geology): Age = Probably Cretaceous or younger. The copper minerals occur in hornblendite dikes which cut metamorphic strata of Paleozoic age.

Comment (Workings): Workings / Exploration = MacKevett and others (1971) reported about 1 percent Cu in samples of hornblendite dikes. Kimball and others (1978) reported 1.8 percent copper in selected samples of copper-rich lenses; the selected samples contained as much as 3 ppm silver and 700 ppm cobalt. There are no mine workings.

Comment (Geology): Geologic Description = The site is in a belt of quartz-feldspar-hornblende paragneiss and gneissic diorite. The protolith of the gneiss is Paleozoic in age; metamorphism occurred in the Cretaceous (Brew and others, 1978). At the site, hornblendite dikes as much as 10 feet thick contain disseminated chalcopyrite and lenses of nearly massive chalcopyrite as much as 2 inches thick and 6 inches long. The dikes cut garnetiferous gneissic diorite.? A grab sample of sulfide-bearing hornblendite collected during the U.S. Geological Survey's 1966 investigation of Glacier Bay contained 10,000 ppm copper by spectrographic analysis (MacKevett and others, 1971, table 9). Kimball and others (1978, p. C270) reported 1.8 percent copper, 3 ppm silver, and 700 ppm cobalt in selected samples of narrow chalcopyrite-rich lenses. ? the dikes appear to be post-Cretaceous metamorphism. They are probably Late Cretaceous or younger in age.

Comment (Reference): Primary Reference = Kimball and others, 1978

Comment (Deposit): Model Name = Disseminated copper deposit in ultramafic (hornblendite) rock.

Comment (Exploration): Status = Inactive

References

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): 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): 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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