Owhat (Cobalt Creek)

Prospect in Alaska, United States with commodities Gold, Copper, Antimony, Tin, Silver, Bismuth, Cobalt, Lead, Zinc

Geologic information

Identification information

Deposit ID 10094086
MRDS ID A013415
Record type Site
Current site name Owhat (Cobalt Creek)
Related records 10282437

Geographic coordinates

Geographic coordinates: -159.11094, 61.66241 (WGS84)
Relative position The Owhat prospect is in the Russian Mountains in the cirque valley at the head of Cobalt Creek. The map site is at the approximate center of sec. 8, T. 18 N., R. 54 W., of the Seward Meridian. This is locality 6 of Hoare and Cobb (1972, 1977), and sample locality 13 of Bundtzen and Laird (1991).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Copper Primary
Antimony Primary
Tin Primary
Silver Secondary
Bismuth Secondary
Cobalt Secondary
Lead Secondary
Zinc Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Bismuth Ore
Bornite Ore
Chalcopyrite Ore
Galena Ore
Gold Ore
Marcasite Ore
Pyrite Ore
Sphalerite Ore
Stephanite Ore
Stetefeldite Ore
Tetrahedrite Ore
Aramayoite Ore
Bismutite Ore
Gladite Ore
Pekoite Ore
Axinite Gangue
Quartz Gangue
Tourmaline Gangue

Alteration

  • (Local) Silicification and tourmalinization.

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 > Granitoid > Quartz Monzonite
    Stratigraphic age (youngest) Pliocene
  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Quartz Monzonite

Nearby scientific data

(1) -159.11094, 61.66241

Comments on the geologic information

  • Geologic Description = The Owhat, or Cobalt Creek prospect was discovered by Native prospectors before 1900 (Maddren, 1915; Holzheimer, 1926). The deposits include 8 to 10 sulfide-tourmaline-axinite-quartz veins or greisens in syeno-monzonite (Bundtzen and Laird, 1991). The individual greisens are several inches to more than 3 feet thick in a zone that is 5 to 26 feet thick; the average width of the zone is about 8 feet ,and it has been traced more than 280 feet vertically. The greisens trend northwest and dip steeply northeast near a contact with an axinite-bearing andesite porphyry dike. The mineralized zone has been traced on the surface for a distance of 870 feet, and extensions totaling 650 feet in both directions are indicated by the distribution of mineralized float. The deposit is mineralogically complex and includes arsenopyrite, aramayoite, bismuth, bismuthite, bornite, chalcopyrite, galena, gold, marcasite, pekoite or gladite, pyrite, sphalerite, stephanite, stetefeldite and tetrahedrite in the sulfide-rich material in the quartz-tourmaline-axinite greisen. Multiple episodes of mineralization are indicated by cross-cutting relations among the veins. Late-forming minerals include arsenopyrite, chalcopyrite, and pyrite, but the youngest cross-cutting assemblages include bornite, stephanite, tetrahedrite, sphalerite, and lead-bismuth sulfides (Bundtzen and Laird, 1991). Microprobe analyses indicate that arsenopyrite contains 0.1 to 0.2 weight percent gold in lattice structures. Bundtzen and Laird (1991) collected 16 chip-channel samples averaging 4.4 feet wide, along 860 feet of the greisen zone. The samples average 5.3 ppm gold, 13.4 percent arsenic, 0.21 percent antimony, 0.39 percent copper, 0.07 percent tin, 0.05 percent zinc, and 0.017 percent cobalt. Assuming dimensions, in feet, of 4.4 x 280 x 870, Bundtzen and Laird (1991) estimated that the resource at this prospect is 63,000 tons of material with the stated average grades. The syeno-monzonite host rocks are part of the Upper Cretaceous intrusive complex of the Russian Mountains (Bundtzen and Laird, 1991).
  • Age = Late Cretaceous or Tertiary. Veins crosscut part of the intrusive complex of the Russian Mountains. Quartz monzonite from this complex has yielded a K/Ar age of 70.3 +/- 2.1 Ma (Bundtzen and Laird, 1991).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Aniak

Comments on the reserve resource information

  • Reserves = Assuming dimensions, in feet, of 4.4 x 280 x 870, Bundtzen and Laird (1991) estimate that the resource at this prospect is 63,000 tons of material with average grades of 5.3 ppm gold, 13.4 percent arsenic, 0.21 percent antimony, 0.39 percent copper, 0.07 percent tin, 0.05 percent zinc, and 0.017 percent cobalt.

Comments on the workings information

  • Workings / Exploration = Three shallow shafts as much as 40 feet deep and several surface trenches and pits explore about 800 feet of strike length of this deposit.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A013415
USGS Alaska Resource Data File ARDF RM016

Bibliographic references

  • Deposit

    Maddren, A.G., 1915, Gold placers of the lower Kuskokwim with a note on copper in the Russian Mountains: U.S. Geological Survey Bulletin 622-H, p. 292-360.

  • Deposit

    Hoare, J M., and Cobb, E.H., 1972, Metallic mineral resources map of the Russian Mission quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-444, scale 1:250,000.

  • Deposit

    Hoare, J.M., and Cobb, E.H., 1977, Mineral occurrences (other than mineral fuels and construction materials) in the Bethel, Goodnews, and Russian Mission quadrangles, Alaska: U.S. Geological Survey Open-File Report 77-156, 98 p.

  • Deposit

    Bundzten, T.K., and Laird, G.M., 1991, Geology and mineral resources of the Russian Mission C-1 Quadrangle, southwest Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 109, 24 p.

  • Deposit

    Hoare, J M., and Cobb, E.H., 1972, Metallic mineral resources map of the Russian Mission quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-444, 1 sheet, scale 1:250,000.

  • Deposit

    Holzheimer, F.W., 1926, Lode prospects in the Russian Mountains, Kuskokwim River region: Alaska Territorial Department of Mines Miscellaneous Report 81-1, 15 p.

Comments on the references

  • Primary Reference = Bundtzen and Laird, 1991

General comments

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

Reporter information

Type Date Name Affiliation Comment
Reporter 10-JUN-01 Travis L. Hudson Applied Geology
Reporter 10-JUN-01 Travis L. Hudson Applied Geology