Mallard Duck Bay

Site Name

Primary: Mallard Duck Bay
Secondary: Calcite
Secondary: Marshinlak

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Commodity

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

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Location

State: Alaska
District: Alaska Peninsula

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Occurrence
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Polymetallic veins
Model Name: Porphyry Cu-Mo
Model Name: Porphyry Cu

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: 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.

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Rocks

Role: Host
Age Type: Host Rock
Age in Years: 24.000000+-3.000000
Age Young: Early Miocene
Age Old: Late Oligocene

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Analytical Data

Not available

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Materials

Ore: Sphalerite
Ore: Arsenopyrite
Ore: Chalcopyrite
Ore: Galena
Ore: Gold
Ore: Pyrite
Gangue: Calcite
Gangue: Quartz
Gangue: Siderite

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Comments

Comment (Deposit): Model Name = Porphyry copper; porphyry copper-molybdenum; polymetallic veins (Cox and Singer, 1986; models 17, 21a, 22c)

Comment (Workings): 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.

Comment (Reference): Primary Reference = Anderson and others, 1979

Comment (Deposit): Model Number = 17, 21a, 22c

Comment (Deposit): Other Comments = This site is on land patented by or interim conveyed to the Bristol Bay Native Corporation.

Comment (Exploration): Status = Inactive

Comment (Geology): Age = The probable age of mineralization is estimated at 21-27 million years (Cox and others, 1981).

Comment (Geology): Age = Chron age is for the host rock.

Comment (Geology): 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.

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References

Reference (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.

Reference (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.

Reference (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.

Reference (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.)

Reference (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.

Reference (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.

Reference (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.)

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

Reference (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.)

Reference (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.

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

Reference (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.

Reference (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.

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