Unnamed (in saddle between Post River and South Fork)

Occurrence in Alaska, United States with commodities Arsenic, Gold, Antimony

Geologic information

Identification information

Deposit ID 10307884
Record type Site
Current site name Unnamed (in saddle between Post River and South Fork)

Geographic coordinates

Geographic coordinates: -153.4448, 62.01348 (WGS84)
Relative position This unnamed occurrence is located in a saddle between tributaries of the Post River and South Fork of the Kuskokwim River; it is at an elevation of 5,150 feet (1,570 m) in the center of sec. 11, T. 22 N., R. 23 W., of the Seward Meridian. The reporter visited the site in 1988; at station no. 88BT164.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Arsenic Primary
Gold Secondary
Antimony Secondary

Comments on the commodity information

  • Gangue = Carbonate

Materials information

Materials Type of material
Arsenopyrite Ore
Quartz Gangue

Alteration

  • (Local) Secondary biotite (potassic) in the border phase.

Mineral occurrence model information

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

Nearby scientific data

(1) -153.4448, 62.01348

Comments on the geologic information

  • Geologic Description = This unnamed occurrence is a low-sulfide, quartz-carbonate vein or veins intruding a border phase of the 37.9 Ma, Hartman Pluton (Solie and others, 1991; Bundtzen, Harris, and Gilbert, 1997). The border phase consists of very fine-grained biotite-rich granodiorite and monzonite. The border phase is in contact with a massive hornfels aureole that is approximately 125 meters wide. A one meter wide, low sulfide, quartz carbonate vein swarm strikes N70W for about 115 meters through the saddle. The veins cuts the intrusive border phase, but apparently die out in the hornfels aureole. Disseminated arsenopyrite and pyrite grains occur near vein margins. One grab sample of the mineralized vein contained 6,500 ppm arsenic, 71 ppb gold, and 250 ppm antimony.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Comments on exploration

  • Status = Inactive

Mining district

District name McGrath

Comments on the workings information

  • Workings / Exploration = The reporter sampled the occurrence during a geologic mapping program for the Alaska Division of Geological and Geophysical Surveys in 1988 (Bundtzen, Harris, and Gilbert, 1997). One grab sample of the mineralized vein contained 6,500 ppm arsenic, 71 ppm gold, and 250 ppm antimony.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF MG088

Bibliographic references

  • 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.

  • 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.

Comments on the references

  • Primary Reference = This description

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 09-DEC-98 T.K. Bundtzen Pacific Rim Geological Consulting