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Unnamed (west arm of Dundas Bay)

Occurrence in Alaska, United States with commodities Copper, Silver, Cobalt
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Geologic information

Identification information

Deposit ID 10002283
MRDS ID A013187
Record type Site
Current site name Unnamed (west arm of Dundas Bay)
Related records 10282452

Geographic coordinates

Geographic coordinates: -136.50208, 58.35583 (WGS84)
Relative position This occurrence is on a small island in the south part of the west arm of Dundas Bay. The island is near the center of section 33, T.40 S., R. 54 E., of the Copper River Meridian. The location is accurate to 0.1 mile. It is the same site as number 67 of Kimball and others (1978) and number 58 of MacKevett and others (1971).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Silver Secondary
Cobalt Secondary

Materials information

Materials Type of material
Chalcopyrite Ore

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Gneiss

Nearby scientific data

(1) -136.50208, 58.35583
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Comments on the geologic information

  • 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.
  • Age = Probably Cretaceous or younger. The copper minerals occur in hornblendite dikes which cut metamorphic strata of Paleozoic age.

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Juneau

Comments on the workings information

  • 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.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A013187
USGS Alaska Resource Data File ARDF MF073

Bibliographic references

  • 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.

  • 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.

  • 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.

Comments on the references

  • Primary Reference = Kimball and others, 1978

General comments

Subject category Comment text
Deposit Model Name = Disseminated copper deposit in ultramafic (hornblendite) rock.
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.

Reporter information

Type Date Name Affiliation Comment
Reporter 14-APR-99 Hawley, C.C. Hawley Resource Group