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North Bradfield River

Unknown in Alaska, United States with commodities Copper, Iron, Silver, Gold, Molybdenum, 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. Mineral occurrence model information
  7. Nearby scientific data
  8. Ore body information
  9. Economic information about the deposit and operations
  10. Mining district
  11. Links to other databases
  12. Bibliographic references
  13. General comments
  14. Reporter information

Geologic information

Identification information

Deposit ID 10003617
MRDS ID A106374
Record type Site
Current site name North Bradfield River
Alternate or previous names Ptarmigan

Geographic coordinates

Geographic coordinates: -131.39153, 56.38559 (WGS84)
Relative position SEE LOCATION COMMENTS

Site location context

Political divisions (FIPS codes)

Wade Hampton(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Bradfield Canal B-5(quadrangle 1:63,360 scale)

Bradfield Canal SW(quadrangle 1:100,000 scale)

Bradfield Canal(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Southern 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)

Geographic areas

Country State
United States Alaska

Comments on the location information

  • THE ABOVE COORDINATES ARE FOR THE APPROXIMATE CENTER OF A GROUP OF MINERAL OCCURRENCES AT AN ELEVATION OF ABOUT 3300 FEET ON A RIDGE IN SECTION 24, BETWEEN TWO FORKS OF UPPER NORTH BRADFIELD RIVER. COBB (1978, LOC. 2-4) GIVES THE FOLLOWING COORDINATES TO ENCOMPASS THE AREA OF THE KNOWN DEPOSITS: LAT. 56.383-56.40N; LONG. 131.383-131.417W. THESE COORDINATES PROBABLY DEFINE THE GEOGRAPHIC LIMITS OF THE KNOWN DEPOSITS WITH AN ACCURACY OF A FEW HUNDRED FEET.

Commodities

Commodity Importance
Copper Primary
Iron Primary
Silver Primary
Gold Primary
Molybdenum Primary
Zinc Critical Primary

Mineral occurrence model information

Model code 62
USGS model code 18d
Deposit model name Skarn Fe

Nearby scientific data

(1) -131.39153, 56.38559
ListMap

Economic information

Ore body information

  • General form SEE DEPOSIT DESCRIPTION COMMENTS

Economic information about the deposit and operations

Commodity type Metallic
Significant No

Comments on exploration

  • Status = Probably inactive

Mining district

District name Petersburg

Comments on the reserve resource information

  • NO ESTIMATES OF RESERVES HAVE BEEN MADE PUBLIC. MOST OF THE MAGNETITE BODIES THAT ARE EXPOSED PROBABLY CONTAIN 50-65% IRON AND 0.1-0.5% CU (MACKEVETT AND BLAKE, 1963, P. D17). ELLIOTT AND KOCH (1981, P. 8, LOC. 9) STATE THAT THE TWO STRUCTURAL INTERPRETATIONS THAT HAVE BEEN PROPOSED (MACKEVETT AND BLAKE, 1963; SONNEVIL, 1981) HAVE DIFFERENT IMPLICATIONS FOR POTENTIAL RESERVES.

Comments on the workings information

  • THE DEPOSIT WAS DISCOVERED IN 1955 AND WAS EXPLORED BY PRIVATE INTERESTS IN THE 1960'S BY SURFACE STRIPPING, AN AIRBORNE MAGNETOMETER SURVEY, AND SIX DIAMOND DRILLHOLES TOTALLING 186 FEET. KOCH (1997, P. 24) REPORTS THAT THE PENDANT IS MARKED BY AN AEROMAGNETIC TROUGH THAT ROUGHLY PARALLELS ITS OUTCROP (U.S. GEOLOGICAL SURVEY, 1979). KOCH (1997, P. 24, 25) AND ELLIOTT AND KOCH (1981, LOC. 9) ALSO REPORT ANOMALOUS AMOUNTS OF AG, AU, MO, AND ZN IN ROCK SAMPLES COLLECTED AT AND NEAR THE NORTH BRADFIELD RIVER DEPOSITS.

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit ELLIOTT AND KOCH (1981) ALSO APPLY THE NAME 'PTARMIGAN' TO THE NORTH BRADFIELD RIVER PROSPECT.
Deposit THE NORTH BRADFIELD RIVER PROSPECT (MACKEVETT AND BLAKE, 1963, P. D1-D21) CONSISTS CHIEFLY OF METASOMATIC, MAGNETITE-SKARN DEPOSITS AT THE NORTHWEST END OF A LARGE ROOF PENDANT OF GNEISS, GRANULITE, SCHIST, MARBLE, AND SKARN IN QUARTZ MONZONITE OF THE COAST RANGE BATHOLITH, WHICH IN TURN IS CUT BY DIKES OF QUARTZ DIORITE, APLITE, AND ALASKITE. THE METAMORPHIC BEDDED ROCKS ARE COMPLEXLY FOLDED. MACKEVETT AND BLAKE (1963, P. D15-D16) INTERPRET THE GENERAL STRUCTURE OF THE PENDANT AS AN OVERTURNED SYNCLINE THAT PROBABLY EXTENDS FOR MANY MILES TO THE SOUTHEAST. SONNEVIL (1981, P. B117), ON THE OTHER, HAND, INTERPRETS THE DOMINANT STRUCTURE IN THE AREA AS A HOMOCLINE WITH NORTHWEST TO NORTHEAST DIPS. KOCH (1997, P. 24) REPORTS THAT THE PENDANT IS MARKED BY AN AEROMAGNETIC TROUGH THAT ROUGHLY PARALLELS ITS OUTCROP (U. S. GEOLOGICAL SURVEY, 1979). THE DEPOSIT IS IN MARBLE UNITS OF THE ROOF PENDANT AND CONSISTS OF CALC-SILICATE SKARN THAT IS PARTLY REPLACED BY MASSIVE MAGNETITE WITH
Deposit INTERSTITIAL PYRRHOTITE; THE MAGNETITE IS CUT BY VEINLETS OF CHALCOPYRITE. THIS ORE CONTAINS SUBORDINATE AMOUNTS OF HEMATITE, LIMONITE, AND MALACHITE. THE OREBODIES, OF WHICH AT LEAST 15 ARE EXPOSED, ARE CRUDELY STRATIFORM AND APPARENTLY DISCONTINUOUS; THEY RANGE IN STRIKE LENGTH FROM 50-350 FEET AND IN THICKNESS FROM 2-40 FEET. KOCH (1997, P. 24-25) SUGGESTS THAT AT LEAST SOME OF THE METAL CONCENTRATION IN THESE DEPOSITS IS RELATED TO THE EMPLACEMENT OF AN EOCENE QUARTZ MONZONITE AND GRANODIORITE STOCK, NEAR THE CONTACT WITH THE MESOZOIC OR PALEOZOIC METAMORPHIC BEDDED ROCKS THAT HOST THE DEPOSITS (ELLIOTT AND KOCH, 1981; KOCH, 1996). KOCH (1997, P. 24, 25) AND ELLIOTT AND KOCH (1981, P. 8, LOC. 9) ALSO REPORT ANOMALOUS AMOUNTS OF AG, AU, MO, AND ZN IN ROCK SAMPLES COLLECTED AT AND NEAR THE NORTH BRADFIELD RIVER DEPOSITS.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-MAY-1998 Berg, H. C. U.S. Geological Survey

Beyond USGS

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

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Authoritative Alaska resources

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