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Cirque

Prospect in Alaska, United States with commodities Silver, Copper, Lead, 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. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10307540
Record type Site
Current site name Cirque

Geographic coordinates

Geographic coordinates: -147.60283, 63.77964 (WGS84)
Relative position The Cirque prospect is at an elevation of about 5,500 feet in a cirque in the south wall of upper West Fork Little Delta River. The map site is in the SW1/4 of sec. 17, T. 13 S., R. 1 E., of the Fairbanks Meridian. The location is accurate to with 2 miles.

Site location context

Political divisions (FIPS codes)

Southeast Fairbanks(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Healy D-2(quadrangle 1:63,360 scale)

Mount Hayes NW(quadrangle 1:100,000 scale)

Healy(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Copper Primary
Lead Primary
Zinc Critical Primary

Materials information

Materials Type of material
Chalcopyrite Ore
Galena Ore
Pyrite Ore
Sphalerite Ore
Quartz Gangue
Sericite Gangue

Alteration

  • (Local) Pyrite and sericite.

Mineral occurrence model information

Model code 184
USGS model code 28a
Deposit model name Massive sulfide, kuroko
Mark3 model number 93

Host and associated rocks

  • Host or associated Host
    Rock type
    Stratigraphic age (youngest) Late Devonian

Nearby scientific data

(1) -147.60283, 63.77964
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The country rocks at the Cirque prospect are Upper Devonian? felsic metavolcanic rocks, chiefly dark- to medium-gray, fine- to medium-grained schist and phyllite, that locally contain relict phenocrysts of quartz, orthoclase, and plagioclase (Wilson and others, 1998). The deposit generally consists of stratiform layers of massive sulfides, chiefly pyrite, chalcopyrite, galena, and sphalerite. Two ore bearing zones have been identified: the Discovery and Dol zones. The Discovery zone is hosted in carbonaceous shale and appears to follow a contact with rhyolite schist. The sulfide layer is massive to banded and can be traced in outcrop for about 20 meters with widths up to 2.8 meters. The zone remains open in both directions but is covered by talus and scree. Surface samples over a 2.4 meter width at the Discovery zone contain an average value of 3.84% zinc, 2.76% lead, and 0.49% copper, plus 3.73 grams gold and 98.5 grams silver per tonne. The Dol zone is in dolomite interbedded with shale. The zone has been traced in scattered outcrops for about 200 meters. All outcrops sampled returned anomalous base and precious metal values. Highlights include a 1-meter chip sample that assayed 5.57% zinc, 2.24% lead, and 0.31% copper, and 0.41 gram gold and 33 grams silver per tonne (The Northern Miner, v. 85, no. 24).
  • Age = Mineralization was probably syngenetic with the Upper Devonian host rocks.

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Active

Mining district

District name Bonnifield

Comments on the workings information

  • Workings / Exploration = Surface exploration mostly includes soil grids, rock-chip sampling and trenching. In 1994, a ground geophysical survey delineated a 670-meter-long electromagnetic anomaly coincident with the Dol zone. There was unknown amount of drilling in 1999. Surface samples over a 2.4 meter width at the Discovery zone contain an average value of 3.84% zinc, 2.76% lead, and 0.49% copper, plus 3.73 grams gold and 98.5 grams silver per tonne. The Dol zone highlights include a 1-meter chip sample that assayed 5.57% zinc, 2.24% lead, and 0.31% copper, and 0.41 gram gold and 33 grams silver per tonne (The Northern Miner, v. 85, no. 24).

Reference information

Comments on the references

  • Primary Reference = the Northern Miner, 1999, v.85, no. 24

General comments

Subject category Comment text
Deposit Model Name = Kuroko massive sulfide (Cox and Singer, 1986; model 28a)

Reporter information

Type Date Name Affiliation Comment
Reporter 07-APR-00 N. Van Wyck Stevens Exploration Management Corporation

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.