Mallard Duck Bay

Occurrence in Alaska, United States with commodities Silver, Gold, Copper, Molybdenum, Lead, Zinc, Arsenic

Geologic information

Identification information

Deposit ID 10001671
MRDS ID A012449
Record type Site
Current site name Mallard Duck Bay
Alternate or previous names Calcite, Marshinlak
Related records 10136770

Geographic coordinates

Geographic coordinates: -158.51356, 56.23039 (WGS84)
Relative position This site represents an area southeast of Chignik Lagoon at the head of Mallard Duck Bay (Berg and Cobb, 1967, locality 2; Cobb, 1972: MF-374, locality 2; MacKevett and Holloway, 1977, locality 2; Cox and others, 1981, locality 8; Nokleberg and others, 1987, locality AP 11). The map site is plotted at an elevation of about 1000 feet, about 0.2 miles southeast of the head of Mallard Duch Bay. The location is accurate to within 1/4 mile.
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Geographic areas

Country State
United States Alaska


Commodity Importance
Silver Primary
Gold Primary
Copper Primary
Molybdenum Primary
Lead Primary
Zinc Primary
Arsenic Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Galena Ore
Gold Ore
Pyrite Ore
Sphalerite Ore
Calcite Gangue
Quartz Gangue
Siderite Gangue


  • (Local) Propylitically altered volcanics cover an area of approximately 6 by 2 1/2 miles. Within this altered zone argillic alteration forms envelopes up to 100 feet wide peripheral to northwest-trending andesite dikes, resulting in a central argillic zone which covers an area of approximately 2 by 1/2 miles.

Mineral occurrence model information

Model code 53
USGS model code 17
Deposit model name Porphyry Cu
Mark3 model number 4
Model code 79
USGS model code 21a
Deposit model name Porphyry Cu-Mo
Mark3 model number 2
Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Host and associated rocks

  • Host or associated Host
    Chronological age 24
    Uncertainty 3
    Stratigraphic age (youngest) Early Miocene
    Stratigraphic age (oldest) Late Oligocene

Nearby scientific data

(1) -158.51356, 56.23039

Comments on the geologic information

  • Geologic Description = This site represents a large propylitically altered zone covering an area 6 miles by 2 1/2 miles at the head of Mallard Duck Bay (Wilson and Cox, 1983). Elevation of the zone varies from sea level to 600 meters. The altered zone is associated with widespread introduction of pyrite and with low-order drainage anomalies (60 ppm copper, 15 ppm molybdenum, 0.3 ppm silver).? Rock types include diorite stocks up to 2000 feet in diameter and a system of northeast-trending quartz-diorite dikes which are up to 1/2 mile in length and up to several hundred feet in thickness. A system of andesite dikes trends N 30 to 40 W and dips vertically across a 4000-foot wide zone. All of these intrusives cut Eocene-Oligocene volcanics of the Meshik Formation which consists of andesite and basalt flows, volcaniclastic breccias, volcaniclastic sediments, and tuffaceous units.? Within the large area of propylitized rock is a zone of intense argillic alteration which covers an area of approximately 2 miles by 1/2 mile. This is referred to as the central argillic zone (Anderson and others 1979). The argillic alteration appears to be related to the northwest-trending andesite dikes because it forms envelopes up to 100 feet wide on either side of the dikes. The altered areas exhibit some silicification and introduction of disseminated pyrite. They also contain coarse stockworks of fractures, some of which contain quartz, pyrite, and rarely molybdenite.? Molybdenum mineralization occurs primarily in a stockwork that lies between two parallel andesite dikes outside of the central argillic zone. The mineralized rock is limonitic and exihibits silicification and minor argillization. As the dikes are approached the alteration increases and the molybdenum mineralization decreases (Anderson and others, 1979). The molybdenum zone has been traced for 100 feet but the total length is unknown. Fields (1977) notes molybdenum values ranging from 2 to 99 ppm in rock samples.? Systems of northwest-trending polymetallic veins are present in the propylitized volcanics. The Calcite and Mallard Duck vein systems occur in an area 1/2 to 1 mile southwest of the central argillic zone. Individual veins are up to 800 feet long and 10 feet wide. Other veins are known to extend along this trend for over 4 miles northwest to the beach exposures at Mallard Duck Bay. The Marshinlak vein system is located approximately 2 miles north of the central argillic zone and has been traced intermittently for over 6500 feet in a northwest direction. These veins are up to 15 feet in thickness. Minor strike trends include northeast, north-south, and east-west. The veins vary in composition from quartz to quartz-calcite to quartz-siderite and may carry up to 5 percent sulfides, including arsenopyrite, chalcopyrite, galena, pyrite, and sphalerite. Some veins exhibit cockscomb features and some show evidence of repetitive pulsing of quartz and sulfides.? Metal values in the Calcite and Mallard Duck systems range as follows: 3360 ppm to 4.2 percent copper, < 0.02 ppm to 3.3 ppm gold, 1100 ppm to 4.45 percent lead, 20 ppm to 21ounces silver ounces per ton, 1100 ppm to 22.7 percent zinc (Butherus and others, 1981). Trace amounts of antimony and mercury were also detected. Copper, lead, and zinc values obtained in the Marshinlak system were all less than 100 ppm. Gold values ranged from 0.48 ppm to 0.163 ounce per ton and silver values from 3.4 ppm to 0.54 ounce per ton.
  • Age = The probable age of mineralization is estimated at 21-27 million years (Cox and others, 1981).
  • Age = Chron age is for the host rock.

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Alaska Peninsula

Comments on the workings information

  • Workings / Exploration = Gold claims were staked in the early part of the century. Bear Creek Mining Company mapped and sampled this zone in 1975 and 1976. Resource Associates of Alaska did detailed mapping and sampling in 1979, 1981, and 1982.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012449
USGS Alaska Resource Data File ARDF CG002

Bibliographic references

  • Deposit

    Atwood, W.W., 1911, Geology and mineral resources of parts of the Alaska Peninsula: U.S. Geological Survey Bulletin 467, 137 p.

  • Deposit

    Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

  • Deposit

    Fields, E.D., 1977, 1976 Annual report: Alaska search, Chignik area-Bristol Bay region: Bear Creek Mining Company, 44 p., 22 map sheets. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Anderson, G.D., Fitch, G.M., Lappie, D.W., Lindberg, P.A., and Fankhauser, R.E., 1979, Exploration and evaluation of Bristol Bay Native Corporation Lands, Vol. II, Book 1: prepared for Houston Oil and Minerals Company by Resource Associates of Alaska, 78 p. (Report held by Alaska Earth Science, Anchorage, Alaska.)

  • Deposit

    Cobb, E.H., 1980, Summaries of data and lists of references to metallic and selected nonmetallic mineral deposits in fifteen quadrangles in southwestern and west-central Alaska: U.S. Geological Survey Open-File Report 80-909, 103 p.

  • Deposit

    Butherus, D.L., White, D.C., Smith, W.H., Radford, G., Sandberg, R.J., and Pray, J.C., 1981, Exploration and evaluation of precious metal potential of Bristol Bay Native Corporation Lands, southwest Alaska, 1981, Vol. 1: Prepared for Nerco by Resource Associates of Alaska, 90 p. (Report held by Alaska Earth Science, Anchorage, Alaska.)

  • Deposit

    Cox, D.P., Detra, D.E., and Detterman, R.L., 1981, Mineral resource maps of the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF- 1053-K, 2 map sheets, scale 1:250,000.

  • Deposit

    Detterman, R.L., Miller, T.P., Yount, M.E., and Wilson, F.H.,1981, Geologic map the Chignik and Sutwik Island quadrangles Alaska: U.S. Geologic Survey Miscellaneous Investigations Series Map I- 1229, 1 map sheet, scale 1:250,000.

  • Deposit

    Wilson, F.H., and Cox, D.P., 1983, Geochronology, geochemistry, and tectonic environment of porphyry mineralization in the central Alaska Peninsula: U.S. Geological Survey Open-File Report 83-783, 24 p.

  • Deposit

    Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Chignik quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-374, 1 sheet, scale 1:250,000.

  • Deposit

    MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.

  • Deposit

    Wilson, F.H., 1980, Late Mesozoic and Cenozoic tectonics and age of porphyry copper prospects, Chignik and Sutwik Island quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 80-543, 94 p., 5 sheets, scales 1:250,000 and 1 inch = 1,000 feet.

Comments on the references

  • Primary Reference = Anderson and others, 1979

General comments

Subject category Comment text
Deposit Model Name = Porphyry copper; porphyry copper-molybdenum; polymetallic veins (Cox and Singer, 1986; models 17, 21a, 22c)
Deposit Model Number = 17, 21a, 22c
Deposit Other Comments = This site is on land patented by or interim conveyed to the Bristol Bay Native Corporation.

Reporter information

Type Date Name Affiliation Comment
Reporter 08-FEB-2000 S.H. Pilcher U.S. Geological Survey