West Fork-Post River

Occurrence in Alaska, United States with commodities Silver, Copper, Zinc

Geologic information

Identification information

Deposit ID 10002604
MRDS ID A015041
Record type Site
Current site name West Fork-Post River
Related records 10185370

Geographic coordinates

Geographic coordinates: -153.88281, 62.00947 (WGS84)
Relative position The West Fork-Post River occurrence is located on an east facing bluff of the west fork of Post River; it is at an elevation of approximately 4,000 feet (1,220 m) in the NE1/4 sec. 8, T. 22 N., R. 25 W., of the Seward Meridian. The occurrence, which corresponds to locality number 19 in Cobb (1972), is located to within 460 m.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Copper Primary
Zinc Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Pyrrhotite Ore
Sphalerite Ore

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock
    Stratigraphic age (youngest) Pliocene
  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Granite
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock

Nearby scientific data

(1) -153.88281, 62.00947

Comments on the geologic information

  • Geologic Description = The West Fork-Post River occurrence consists of small lenses and disseminations of pyrrhotite associated with a swarm of northwest-trending mafic dikes that cut argillite of the Early to Late Silurian Terra Cotta Mountains Sandstone, a unit of the Dillinger subterrane (Bundtzen and others, 1988; Bundtzen, Harris, and Gilbert, 1997). Samples collected by Reed and Elliott (1968, C 596) contained semi-massive pyrrhotite and minor chalcopyrite and sphalerite. Values from selected grab samples on the surface run up to 45.7 grams/tonne silver, 1.50 percent copper, and 0.07 percent zinc.

Economic information

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 = The West Fork-Post River was discovered by the late Bruce Reed during mineral investigations for the U.S. Geological Survey in the 1960s (Reed and Elliott, 1968, C 596). Values from selected grab samples collected by Reed and Elliott (1968, C 596) contain up to 45.7 grams/tonne silver, 1.50 percent copper, and 0.07 percent zinc.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A015041
USGS Alaska Resource Data File ARDF MG073

Bibliographic references

  • Deposit

    Reed, B.L. and Elliott, R.L., 1968, Geochemical anomalies and metalliferous deposits between Windy Fork and Post River, southern Alaska: U.S. Geological Survey Circular 596, 22 pages.

  • Deposit

    Reed, B.L., and Elliott, R.L., 1968, Results of stream sediment sampling in parts of the southern Alaska Range: U.S. Geological Survey Open-File Report, 9 pages, one sheet, 1:500,000 scale.

  • Deposit

    Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 pages, one sheet, scale 1:125,000.

  • Deposit

    MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.

Comments on the references

  • Primary Reference = Reed and Elliott, 1968 (C 596)

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein (Cox and Singer, 1986; model 22c).
Deposit Other Comments = Similar to Veleska-South prospect (MG050) in McGrath B-2 quadrangle.

Reporter information

Type Date Name Affiliation Comment
Reporter 30-OCT-1998 T.K. Bundtzen Pacific Rim Geological Consulting