PMRGX-21 (Mud Bay)

Prospect in Alaska, United States with commodities Silver, Copper, Lead, Zinc, Arsenic, Bismuth, Cadmium, Antimony

Geologic information

Identification information

Deposit ID 10308107
Record type Site
Current site name PMRGX-21 (Mud Bay)

Geographic coordinates

Geographic coordinates: -160.51414, 55.72934 (WGS84)
Relative position This prospect is located on the Alaska Peninsula approximately 4 miles southwest of the head of Mud Bay on Port Moller and about 5.5 miles east of the head of Herendeen Bay. The map site is at an elevation of 1,550 feet, 0.2 mile southwest of the top of hill 1750, in the SE1/4 of sec. 26, T. 51 S., R. 73 W., of the Seward Meridian. It is referred to as PMRGX-21(Mud Bay) in Wilson and others (1988, locality 86). The location is accurate to within 500 feet.
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Geographic areas

Country State
United States Alaska


Commodity Importance
Silver Primary
Copper Primary
Lead Primary
Zinc Primary
Arsenic Secondary
Bismuth Secondary
Cadmium Secondary
Antimony Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Gold Ore
Pyrite Ore
Sphalerite Ore
Tetrahedrite Ore
Galena Ore
Silver Ore
Calcite Gangue
Quartz Gangue


  • (Local) Alteration at this prospect includes silicification, argillization, sericitization, and carbonate-chlorite replacement.

Mineral occurrence model information

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

Nearby scientific data

(1) -160.51414, 55.72934

Comments on the geologic information

  • Geologic Description = This prospect was first staked by Resource Associates of Alaska in 1980. They outlined a mineralized system 3.5 miles long by as much as 1 mile wide that trends east-west. The system is hosted by sedimentary rocks of the Eocene to Oligocene Stepovak Formation (Wilson and others, 1995). The rocks are cut by dikes and sills varying from andesite to rhyodacite (Trujillo and others, 1982). The mineralized system is intensely silicified and is marked by widespread pyrite that occurs as fracture fillings and as disseminations. A carbonate-chlorite alteration halo as wide as 800 feet surrounds the silicified zone, which is characterized by irregular quartz-sericite masses and apparently randomly distributed quartz veins. The silicified zone also contains local zones of argillic alteration, especially adjacent to dikes and sills and to quartz-sulfide veins. The best mineralization found by Trujillo and others (1982) was along the northern edge of the silicified zone, where there are sulfide-bearing quartz veins a few inches to as much as 2 to 3 feet wide. These veins are mostly in the silicified zone and are as much as 300 feet long. They contain massive galena, coarse-grained sphalerite, blebs, and stringers of chalcopyrite, and rare tetrahedrite. A 13.8-foot channel sample assayed 15.4 ounces of silver per ton, 0.46 percent copper, 5.73 percent lead, and 4.37 percent zinc. Selected samples of 1- to 3-foot-wide veins assayed 0.01 to 0.098 ounce of gold per ton, 23.7 to 160 ounces of silver per ton, 0.2 to 0.4 percent copper, 2.9 to 5.2 percent lead, and 0.8 to 12.3 percent zinc (Trujillo and others, 1982). Other types of mineralization in the silicified zone include stockworks of galena-calcite veins as much as 1 inch thick, and pyrite disseminated in fractured rocks. The latter type contains only pyrite but assayed as much as 1.54 ounces of silver per ton. Disseminated sulfides in the carbonate-chlorite alteration zone also carry silver. Soil geochemistry indicates mercury enrichment in the carbonate-chlorite zone adjacent to the silicified zone. Gold anomalies occur sporadically and are most common in the area of mercury enrichment. Some base metal anomalies are related to dikes or dike swarms in the silicified zone. In 1984 Freeport Exploration Drilling Company geologists outlined an apparent eastward extension of the deposit. It was their opinion, however, that the rocks were hornfelsed rather than silicified. They were discouraged by this fact and by what they described as weak geochemisty and alteration and the consistently narrow veins.
  • Age = Eocene or younger.

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name Alaska Peninsula

Comments on the workings information

  • Workings / Exploration = Resource Associates of Alaska explored this prospect from 1980 to 1982. During that time they mapped and hand trenched the prospect, collected 222 rock and 423 soil samples, and conducted VLF-EM and magnetic surveys. Selected samples of 1- to 3-foot wide veins assayed 0.01 to 0.098 ounce of gold per ton, 23.7 to 160 ounces of silver per ton, 0.2 to 0.4 percent copper, 2.9 to 5.2 percent lead, and 0.85 to 12.3 percent zinc. In 1984 Freeport Exploration Drilling Company did additional mapping and trenching and collected 143 rock and 47 soil samples. Six rock samples collected by the U.S. Geological Survey in the mid-1980s were anomalous in copper, lead, zinc, silver, arsenic, bismuth, and antimony (Wilson and others, 1988).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF PM031

Bibliographic references

  • Deposit

    Butherus, D.L, Gressitt, E.E., Pray, J., Corner, N.G., Lindberg, P.H., and Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation lands; Volume III: Resource Associates of Alaska, 69 p. 90 sheets, various sacales. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)

  • Deposit

    Anderson, G.L., Butherus, D.L., Fankhauser, R.E., Pray, J.C., Lindberg, P.A., and Hoffman, B.L., 1980, Exploration and evaluation of lands leased from Aleut Native Corporation 1980; Resource Associates of Alaska Report, 84 p, 16 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Trujillo, R.S., Tapper, C.J., Alvarez, T.J., Porterfield, Ben, and Toupe, W.M., 1982, Exploration and evaluation of precious metal potential of portions of Aleut Corporation lands, southwest Alaska 1982: Unpublished Resource Associates of Alaska report, 91 p, 33 mpas, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • 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.)

  • Deposit

    Wilson, F.H., Harris, E.E., and Bailey, E.A., 1987, Preliminary analytical results and sample locality map for rock samples collected in 1985 and 1986, Port Moller and Stepovak Bay quadrangles, Alaska: U.S. Geological Survey Open-File Report 87-497, 44 p., 1 plate, scale 1:250,000.

  • 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.

  • 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.

Comments on the references

  • Primary Reference = Trujillo and others, 1982

General comments

Subject category Comment text
Deposit Model Name = Polymetallic veins (Cox and Singer, 1986; model 22c)
Deposit Other Comments = This site is located on state land.

Reporter information

Type Date Name Affiliation Comment
Reporter 28-JAN-01 S.H. Pilcher U.S. Geological Survey