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Post River Pluton

Prospect in Alaska, United States with commodities Silver, Copper, Tin, Tungsten, Gold, Lead
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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 10307868
Record type Site
Current site name Post River Pluton

Geographic coordinates

Geographic coordinates: -153.66781, 62.08248 (WGS84)
Relative position The Post River Pluton prospect is located in a saddle 10 kilometers southwest of Post Lake at an elevation of 5,400 feet (1,646 m) in the NW1/4 sec. 15, T. 23 N., R. 24 W., of the Seward Meridian. The prospect corresponds to map number 6a, b in Bundtzen and others (1988) and map number 28 in Bundtzen, Harris, and Gilbert (1997). The reporter investigated the site in 1982.

Site location context

Political divisions (FIPS codes)

Bethel(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

McGrath A-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
Silver Primary
Copper Primary
Tin Critical Primary
Tungsten Critical Primary
Gold Secondary
Lead Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Pyrite Ore
Scheelite Ore
Calcite Gangue
Quartz Gangue

Alteration

  • (Local) Secondary biotite (potassic).

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
    Stratigraphic age (youngest) Paleocene
    Chronological age 60.4
    Dating method K-Ar

Nearby scientific data

(1) -153.66781, 62.08248
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The Post River Pluton prospect is a chalcopyrite-scheelite-quartz vein system that cuts sheared, thermally altered shale of the Lower Ordovician to Lower Silurian Post River Formation; the unit is intruded by an early Tertiary quartz monzonite pluton (Bundtzen and others, 1988). The largest vein, which reaches a maximum one meter wide, trends across the saddle in a N40E direction for about 84 meters. Smaller en echelon veins and veinlets also trend in a northeasterly direction. Lack of good bedrock control prevented any systematic dip or size measurements. A strong secondary biotite overprint occurs in the thermally altered shales. . Principle mineralization consists of disseminated scheelite-chalcopyrite aggregates in quartz-calcite veins, and pyrite in hornfels. Bundtzen and others (1988) report values of 98.0 grams/tonne silver, 1.15 percent copper, 0.18 percent lead, 275 ppm tungsten, and 890 ppm tin from five chip-channel samples. Tin and lead minerals were not identified. One sample contained 900 ppb gold. A one meter wide zone of pyrite-rich hornfels contained 759 ppm copper and 0.8 grams/tonne silver. A pan concentrate from a steep ravine draining the mineralized area contained 59.0 grams/tonne silver and abundant visible scheelite.
  • Age = Undated; nearby quartz monzonite pluton yielded K-Ar age of 60.4 Ma (Solie and others, 1991).
  • Age = Chronological age is for the nearby quartz monzonite pluton.

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name McGrath

Comments on the workings information

  • Workings / Exploration = T.K. Bundtzen and M.S. Lockwood found the mineralized area during geologic mapping for the Alaska Division of Geological and Geophysical Surveys in 1982. Bundtzen and others (1988) report values of 98.0 grams/tonne silver, 1.15 percent copper, 0.18 percent lead, 275 ppm tungsten, and 890 ppm tin from five chip-channel samples. Tin and lead minerals were not identified. One sample contained 900 ppb gold. A one meter wide zone of pyrite-rich hornfels contained 759 ppm copper and 0.8 grams/tonne silver. A pan concentrate from a steep ravine draining the mineralized area contained abundant visible scheelite and 59.0 grams/tonne silver.

Reference information

Comments on the references

  • Primary Reference = Bundtzen and others, 1988

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein (Cox and Singer, 1986; model 22c),

Reporter information

Type Date Name Affiliation Comment
Reporter 08-DEC-98 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.