Four Bear

The Four Bear is a lead, copper, gold, zinc, and silver 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: Four Bear
Secondary: Pmrgx-28

Commodity

Primary: Lead
Primary: Copper
Primary: Gold
Primary: Zinc
Primary: Silver
Secondary: Arsenic
Secondary: Mercury

Location

State: Alaska
District: Alaska Peninsula

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: Porphyry Cu
Model Name: Porphyry Cu-Au

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Alteration ranges from propylitic to argillic to sericitic, along with local silicification.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Sphalerite
Ore: Pyrite
Gangue: Tourmaline
Gangue: Quartz
Gangue: Opal
Gangue: Calcite

Comments

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Tertiary.

Comment (Reference): Primary Reference = Freeport Exploration Company, 1985

Comment (Deposit): Model Number = 17, 20c

Comment (Deposit): Other Comments = the site is located on land patented by, or interim-conveyed to, the Aleut Corporation.

Comment (Workings): Workings / Exploration = In 1983, Resource Associates of Alaska mapped the prospect and collected 87 rock and soil samples. The highest metal values in their rock samples were as much as 0.08 ppm gold, 5.5 ppm silver, 273 ppm copper, 450 ppm lead, 544 ppm zinc, 595 ppm arsenic, and 0.08 ppm mercury. In 1984, Freeport Exploration Company mapped the prospect and took 41 rock and 106 soil samples. Six samples contained anomalous gold values.

Comment (Geology): Geologic Description = At the Four Bear prospect, siltstone, shale, sandstone, and conglomerate of the Upper Cretaceous Hoodoo Formation are cut by intrusive rocks that include diorite and rhyolite-rhyodacite quartz porphyry (Wilson and others, 1995). The diorite exhibits propylitic, argillic, and sericitic alteration. The younger rhyolite-rhyodacite quartz porphyry forms the central part of the prospect area. It contains as much as 20 percent disseminated pyrite and is pervasively sericitized. Locally, it is silicified and contains small stockworks of thin pyrite veins. Quartz and quartz-calcite veins 0.25 to 2 inches wide occur in widely scattered shears (Freeport Exploration Company, 1985). Pebble and breccia dikes occur in the intrusives and in the surrounding sedimentary rock. Opal and sphalerite occur in the dikes. Tourmaline is present in a breccia pipe. The sedimentary rocks are intensely hornfelsed and iron stained up to 1,000 feet from the intrusive rocks. Resource Associates of Alaska outlined a gold soil anomaly area of approximately 1,000 by 2,000 feet and an arsenic soil anomaly area of 3,000 by 3,500 feet (Trujillo and others, 1983). Their soil samples contained as much as 0.21 ppm gold, and their rock samples contained as much as 0.08 ppm gold, 5.5 ppm silver, 273 ppm copper, 450 ppm lead, 544 ppm zinc, 595 ppm arsenic, and 0.08 ppm mercury. Freeport Exploration Company collected six rock samples that had anomalous gold values. The tourmaline-bearing breccia contained 0.11 ppm gold and 1.4 ppm silver.

Comment (Deposit): Model Name = Porphyry Cu, Porphyry Cu-Au (Cox and Singer, 1986; models 17, 20c)

References

Reference (Deposit): Angeloni, L.M., Wilson, F.H., and Sutlet, S., 1985, Map and tables showing preliminary rock geochemical data, Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Open-File Report 85-470, 179 p., 1 map sheet, scale 1:250,000.

Reference (Deposit): Wilson, F.H., Detterman, R.L., Miller, J. W., and Case, J.E., 1995, Geologic map of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigation Series Map I-2272, 1 map sheet, scale 1:250,000.

Reference (Deposit): Wilson, F.H., White, W.H., and DuBois, G.D., 1988, Brief descriptions of mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 88-666, 128 p., scale 1:250,000.

Reference (Deposit): Freeport Exploration Company, 1985, 1984 report of activities, Canoe Bay joint venture: Freeport Exploration Company, 25 p. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Reference (Deposit): Trujillo, R.S., Farnham, S., and Anderson, G.,1983, Exploration and evaluation of precious metal potential of the Aleut Corporation 14(h)8 lands, southwest Alaska: Resource Associates of Alaska report, 25 p., 11 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

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