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Northern Copper Company

Prospect in Alaska, United States with commodities Copper, Zinc
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Host and associated rocks
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10000279
MRDS ID A010323
Record type Site
Current site name Northern Copper Company
Alternate or previous names Tower Arm Copper, Portage Bay Copper Company
Related records 10112948

Geographic coordinates

Geographic coordinates: -133.37496, 56.88668 (WGS84)
Relative position Northern Kupreanof Island; on a southern spur of Kupreanof Mountain at an elevation of about 1350 feet in the center of the northern half of section 36, T. 57 S., R. 76 E. Prospect is heavily overgrown and is not easy to locate on the ground. Locality 12 of Grybeck, Berg, and Karl (1984).

Site location context

Political divisions (FIPS codes)

Wade Hampton(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Petersburg D-5(quadrangle 1:63,360 scale)

Petersburg N(quadrangle 1:100,000 scale)

Petersburg(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Central Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Tongass National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Petersburg Creek-Duncan Salt Chuck Wilderness(Wilderness)

Wilderness FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Zinc Critical Primary

Materials information

Materials Type of material
Chalcopyrite Ore
Magnetite Ore
Pyrrhotite Ore
Sphalerite Ore

Alteration

  • (Local) Unclear.

Host and associated rocks

  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Granite

Nearby scientific data

(1) -133.37496, 56.88668
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Mineralization occurs as pods and irregular masses of magnetite, sphalerite, pyrrhotite, and chalcopyrite in a locally garnet-bearing, equigranular, pyroxene-rich porphyritic greenstone associated with minor coarse-grained marble. The older literature identifies the host rock as 'pyroxene granulite', but the lithology of the host rock and the origin of the deposit are enigmatic; the mineralized greenstone appears skarn-like locally. The sulfides are either interstitial to pyroxene in the greenstone or replace massive fine-grained greenstone. Drilling in the late 1970's by AMOCO Minerals (oral communication, 1981) indicate that the greenstone is underlain at shallow depth by green siliceous phyllite, which is in turn underlain by black carbonaceous argillite. Sulfides frequently occur in bands parallel to the compositional layering of the greenstone. Analyses of selected sulfide-bearing samples show major Cu and Zn commensurate with the visible mineralogy, less than 0.05 ppm Au and up to 5 ppm Ag. (Description synthesized from Wright and Wright, 1908, p. 41-142, Buddington, 1923, p. 70-72; Roehm, 1945 [DGGS IR 195-37]; Twenhofel and others, 1949, p. 37-38; personal communications from AMOCO Minerals who drilled the property in the late 1970's; and field work by the reporters that was summarized in Grybeck, Karl, and Berg, 1984.) ? Brew and others (1984) mapped the country rocks in the vicinity as part of a regionally extensive, undifferentiated Mesozoic volcanic unit.
  • Age = Unknown.

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Probably inactive

Mining district

District name Kupreanof

Comments on the production information

  • Production Notes = None

Comments on the reserve resource information

  • Reserves = None

Comments on the workings information

  • Workings / Exploration = Prospect active from 1900 to 1921 with several hundred feet of underground workings, and considerable trenching; a road was built part way to the prospect from the head of Duncan Canal. The prospect was restaked in 1978 and was drilled in 1978 and 1979; the results of this work have not been made public but the drill results were not encouraging (oral communication, AMOCO Minerals, 1980). There has apparently been no further surface work on the property through the summer of 1996.

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit Model Name = An enigma, possibly a skarn (but probably not a volcanogenic massive sulfide deposit).

Reporter information

Type Date Name Affiliation Comment
Reporter 01-NOV-98 H.C. Berg U.S. Geological Survey
Reporter 01-NOV-98 D.J. Grybeck U.S. Geological Survey

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.