Post River Pluton

The Post River Pluton is a silver, tin, tungsten, and copper mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Post River Pluton

Commodity

Primary: Silver
Primary: Tin
Primary: Tungsten
Primary: Copper
Secondary: Gold
Secondary: Lead

Location

State: Alaska
District: McGrath

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Polymetallic veins

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Secondary biotite (potassic).

Rocks

Role: Associated
Age Type: Associated Rock
Age in Years: 60.400000+-
Dating Method: K-Ar
Age Young: Paleocene

Analytical Data

Not available

Materials

Ore: Scheelite
Ore: Pyrite
Ore: Chalcopyrite
Gangue: Quartz
Gangue: Calcite

Comments

Comment (Geology): Age = Undated; nearby quartz monzonite pluton yielded K-Ar age of 60.4 Ma (Solie and others, 1991).

Comment (Reference): Primary Reference = Bundtzen and others, 1988

Comment (Geology): Age = Chronological age is for the nearby quartz monzonite pluton.

Comment (Workings): 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.

Comment (Exploration): Status = Inactive

Comment (Geology): 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.

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

References

Reference (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.

Reference (Deposit): Solie, D.N., Bundtzen, T.K., and Gilbert, W.G., 1991, K-Ar ages of igneous rocks in the McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 160, 17 pages, one sheet, 1:250,000 scale.

Reference (Deposit): Bundtzen, T.K., Kline, J.T., Smith, T.E., and Albanese, M.D., 1988, Geology of the McGrath A-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 91, 18 p., 1sheet, scale 1:63,360.

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