Pumicestone Bay

The Pumicestone Bay is a gold 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: Pumicestone Bay

Commodity

Primary: Gold
Primary: Silver
Secondary: Lead
Secondary: Barium-Barite
Secondary: Zinc

Location

State: Alaska
District: Aleutians

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: Epithermal vein, generic
Model Name: Polymetallic veins

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Rocks are regionally propylitically altered and also hornfelsed as a result of proximity to the Shaler batholith (Simpson, 1986). Highest gold grades are associated with zones of 'pyrite-silica' alteration in 'spotted andesite' (Simpson, 1986).

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chalcopyrite
Ore: Galena
Ore: Pyrite
Ore: Sphalerite
Gangue: Chlorite
Gangue: Epidote
Gangue: Magnetite
Gangue: Specularite

Comments

Comment (Geology): Geologic Description = Christie (1974) reported a single 3,000 ft (900 m) by 1,500 ft (450 m) color anomaly whereas later evaluations by Randolph and Ellis (1989) and Randolph (1991) described three color anomalies aligned along a steep valley wall. Country rock is the Unalaska Formation (see Drewes and others, 1961), near a sheared contact with the Shaler batholith. Granodiorite of the pluton occurs below the color anomalies at elevations below about 600 feet (200 m). Prospect lies at contact with metamorphosed impure sandstone, breccia, and quartz pebble conglomerate. Stockwork veining and silicification is locally developed within an exposed volume of 1600 by 160 feet, having a 75 foot thickness (80 x 50 x 20 m). Semi-parallel northeast-trending shear zones cut off the quartz stockwork and silicification to the northwest. Quartz veining occurs parallel and/or marginal to these shear zones. Largest of these quartz veins is about 1 foot (30 cm) wide, gossanous, and contains up to 20 percent pyrite (Randolph, 1991) and rare chalcopyrite, sphalerite, and/or galena (Christie, 1974; Randolph, 1991). Randolph's (1991) interpretation was that there were two episodes of veining, where the sulfide-bearing shear-hosted veins cut the earlier quartz stockwork.

Comment (Geology): Age = Miocene or younger

Comment (Exploration): Status = Inactive

Comment (Workings): Workings / Exploration = Battle Mountain Exploration Co. (BMEC) established a sampling grid over one exposure of hornfelsed volcaniclastic rocks and/or graywacke that has been strongly stockworked and silicified. Quartz stringer densities were as high as 2 per inch (2.54 cm) and only rarely contain visible sulfides. The quartz stockwork contained gold to 272 ppb and slightly anomalous lead and barium. Quartz veins hosted in the northeast-trending shear zones contain up to 275 ppb gold, 31.5 ppm silver, 0.24 percent lead, 0.14 percent zinc, elevated barium and insignificant mercury and arsenic (Randolph, 1991).

Comment (Reference): Primary Reference = Randolph, 1991

Comment (Deposit): Model Name = Polymetallic vein, epithermal gold vein

Comment (Deposit): Model Number = 22c, 25

Comment (Deposit): Other Comments = Randolph (1991) gave the prospect a poor potential for economic gold mineralization due to remoteness, ruggedness of the environment, and minimal evidence for economic mineralization.

References

Reference (Deposit): Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Reference (Deposit): Randolph, D.B., and Ellis, W.T., 1989, Unalaska project, 1989 final report: Battle Mountain Exploration Company, Alaska District, 41 p., 5 appendices, 11 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Reference (Deposit): Drewes, Harold, Fraser, G.D., Snyder, G.L., and Barnett, H.F., Jr., 1961, Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska: U.S. Geological Survey Bulletin 1028-S, p. 583-676.

Reference (Deposit): Randolph, D.B., 1991, Unalaska project, 1990 final report: Battle Mountain Exploration Company, Alaska District, 62 p., 5 appendices, 15 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Reference (Deposit): Simpson, D.F., 1986, Aleutian Islands project, 1985 final report: Kennecott Alaska Exploration Company, 54 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)

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