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Unnamed

Occurrence in Alaska, United States with commodities Copper, Iron, Nickel, Bismuth, Chromium
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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. Mineral occurrence model information
  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 10308654
Record type Site
Current site name Unnamed

Geographic coordinates

Geographic coordinates: -153.96285, 62.38848 (WGS84)
Relative position The unnamed occurrence is located on a sharp northwest-trending ridge immediately north of a 5,550 foot (1,692 m) knob on the USGS McGrath B-2 1:63,360 quadrangle at an elevation of 5,540 feet (1,689 m) in the NW1/4 sec. 32, T. 27 N., R. 25 W., of the Seward Meridian. The reporter found the site in 1981 and 1989; at station no. 81BT549.

Site location context

Political divisions (FIPS codes)

Yukon-Koyukuk(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

McGrath B-2(quadrangle 1:63,360 scale)

McGrath SE(quadrangle 1:100,000 scale)

McGrath(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Upper Kuskokwim River(hydrologic accounting unit)

Southwest(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Iron Primary
Nickel Critical Primary
Bismuth Critical Secondary
Chromium Critical Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Pyrite Ore
Pyrrhotite Ore
Magnetite Gangue

Alteration

  • Chalcedonic, carbonate.

Mineral occurrence model information

Model code 10
USGS model code 5b
Deposit model name Noril'sk Cu-Ni-PGE

Nearby scientific data

(1) -153.96285, 62.38848
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = This unnamed occurrence consists of disseminated sulfides in a differentiated picrite-diorite sill that intrudes highly altered chert, sandstone, and siltstone of the Middle Devonian to Permian Sheep Creek Formation, a unit of the Mystic subterrane (Bundtzen, Harris, and Gilbert, 1997). The 15- meter-thick, mafic sill trends roughly EW and dips about 35N. Exposures continue along strike for about 3 kilometers before dipping below talus cover on both ends. Locally, the sill has produced a large 150-meter-wide alteration area in the sedimentary rocks, which is composed of chalcedonic-carbonate replacement of both country rock and the sill itself. The differentiated sill is interpreted by Bundtzen, Harris, and Gilbert (1997) to be a feeder for mafic volcanism in the overlying Late Triassic to Lower Jurassic Tatina River Volcanics. Mineralization appears at the base of the sill, and consists of abundant magnetite, pyrite, pyrrhotite, and traces of chalcopyrite. The size of the mineralized area was not determined. Samples of the sill are composed of up to 50 percent coarse grained magnetite interlocked with silicate melt minerals of magmatic origin. Some network style pyrite-pyrrhotite-magnetite zones contain up to 200 ppm copper, 600 ppm nickel, 100 ppm bismuth, and 1,000 ppm chromium (Bundtzen, Kline, and Clough, 1982; Bundtzen, Harris, and Gilbert, 1997). Anomalous copper and chromium values were found in stream sediment samples taken in the area (Reed and Elliott, 1968, OFR).
  • Age = Sill assigned a Late Triassic age by Bundtzen, Harris, and Gilbert (1997).

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name McGrath

Comments on the workings information

  • Workings / Exploration = Surface samples contain up to 200 ppm copper, 600 ppm nickel, 100 ppm bismuth, and 1,000 ppm chromium (Bundtzen, Kline, and Clough, 1982). Anomalous copper and chromium values were found in stream sediment samples taken in the occurrence area (Reed and Elliott, 1968, OFR).

Reference information

Comments on the references

  • Primary Reference = This description

General comments

Subject category Comment text
Deposit Model Name = Disseminated copper-nickel-cobalt (Cox and Singer, 1986; model 5b).
Deposit Other Comments = Similar to Roberts PGM (MG030) and Chip Loy (MG032) prospects in McGrath A-3 quadrangle.

Reporter information

Type Date Name Affiliation Comment
Reporter 05-DEC-1998 T.K. Bundtzen Pacific Rim Geological Consulting

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.