Unnamed (south of Zachary Bay)

Prospect in Alaska, United States with commodities Gold, Copper, Molybdenum

Geologic information

Identification information

Deposit ID 10308130
Record type Site
Current site name Unnamed (south of Zachary Bay)

Geographic coordinates

Geographic coordinates: -160.63542, 55.25323 (WGS84)
Relative position This prospect is located on Unga Island approximately 2 miles south of Zachary Bay (Christie, 1974, color anomaly 92; Wilson and others, 1988, locality 48). The map site is at an elevation of 700 feet, about 0.4 mile west of the enter of sec. 3, T. 57 S., R. 75 W., Seward Meridian. The location is accurate to within 1,000 feet.
(click for info)

Geographic areas

Country State
United States Alaska


Commodity Importance
Gold Primary
Copper Primary
Molybdenum Secondary

Materials information

Materials Type of material
Chalcocite Ore
Chalcopyrite Ore
Molybdenite Ore
Pyrite Ore
Quartz Gangue


  • (Local) Propylitic alteration consisting of various combinations of epidote, chlorite, pyrite, and magnetite is widespread. Quartz-sericite-pyrite, magnetite-plagioclase, and potassic (biotite) assemblages are also present. .Alteration zoning is poorly understood due primarily to lack of outcrop. One zoning sequence of increasing intensity consists of epidote-pyrite to chlorite-pyrite to chlorite-magnetite.

Mineral occurrence model information

Model code 53
USGS model code 17
Deposit model name Porphyry Cu
Mark3 model number 4
Model code 78
USGS model code 20c
Deposit model name Porphyry Cu-Au
Mark3 model number 34

Nearby scientific data

(1) -160.63542, 55.25323

Comments on the geologic information

  • Geologic Description = This prospect is marked by a color anomaly measuring 2,000 by 5,000 feet. The rocks consist of a series of andesitic volcanic rocks and interbedded volcanic sediments intruded by quartz diorite and feldspar porphyry. A diorite plug forms the core of the anomaly. The diorite is only slightly altered and contains 1 percent disseminated pyrite. Andesites in contact with this intrusive carry pyrite and a trace of chalcopyrite. The volcanic rocks belong to the late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995). A potassium argon date on sericite from the diorite was determined to be 14.6 Ma (Wilson and others, 1994). Copper-gold mineralization occurs in scattered outcrops in an area (including cover) 4,000 feet in diameter. Chalcopyrite is the only primary copper mineral. The other primary sulfides are pyrite and molybdenite. Chalcocite is generally present in outcrops containing 500 ppm copper or greater. The main showing consists of 150 feet of hornfels containing 0.36 percent copper, 0.004 percent molybdenum, 0.08 ounce of silver per ton, and 0.16 ounce of gold per ton (Christie and Richards, 1974). Peripheral outcrops contain much lower metal values. Approximately 600 feet northeast of the main showing, an outcrop of quartz-veined and pyritic feldspar porphyry carries as much as 0.76 percent copper and 0.10 ounce of gold per ton. The sulfides at this outcrop have been almost totally leached. An outcrop to the south carries as much as 1,720 ppm copper (Dircks and Richards, 1976). Three of four holes drilled in 1975 penetrated only short intervals grading 0.1 percent copper. The other hole was drilled through 383 feet grading 0.11 percent copper and 0.28 ppm gold.
  • Age = Miocene 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 = This prospect was mapped and sampled by an Aleut-Quintana-Duval joint venture in 1974. They collected more than 150 rock, silt, and soil samples. In 1975 they conducted a magnetometer survey and drilled four holes for a total of 955 feet. They reported channel samples assays of 0.36 percent copper, 0.004 percent molybdenum, 0.016 ounce of gold per ton, and 0.08 ounce of silver per ton over 150 feet. Drill hole Z-1 intersected 383 feet grading 0.11 percent copper and 0.28 ppm gold. Resource Associates of Alaska relogged, split, and assayed the core in 1981. They were interested primarily in gold values. The results were not encouraging (Trujillo and others, 1981). Battle Mountain Exploration company briefly sampled the area in 1986.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF PM057

Bibliographic references

  • 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.)

  • Deposit

    Christie, J.S., and Richards, G.G., 1974, Zachary Bay color anomaly and copper-gold prospect Unga Island Alaska, Port Moller B-2 quadrangle: Quintana Minerals Report, 9 p. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Dircks, N.J., and Richards, G.G., 1976, Final report on Zachary Bay project Unga Island, Alaska Port Moller B-2 quadrangle: Quintana Minerals, 10 p. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Trujillo, R.S., Anderson, G., MacLeod, T., Hendrick, K., Farnham, S., Peterson, J., 1981. Exploration and evaluation of the Unga-Popof-Korovan Islands portion of lands leased from Aleut Native Corporation: Resource Associates of Alaska report, 70 p., 38 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • 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., Shew, N., DuBois, G.D., and Bie, S.W., 1994, Sample locality map and analytical data for potassium-argon ages in the Port Moller, Stepovak Bay and Simeonof Island quadrangles, Alaska Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2155-E, 18 p., 1 map sheet, 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.

  • Deposit

    Christie, J.S., 1975, Aleut-Quintana-Duval 1975 joint venture, preliminary report: Quintana Minerals Report, 6 p., 9 map sheets, scales 1:63.360 and 1 inch equals 800 feet. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Comments on the references

  • Primary Reference = Dircks and Richards, 1976

General comments

Subject category Comment text
Deposit Model Name = Porphyry Cu, Porphyry Cu-Au (Cox and Singer, 1986; models 17, 20c)
Deposit Model Number = 17, 20c
Deposit Other Comments = This prospect is located on land selected by the Aleut Corporation.

Reporter information

Type Date Name Affiliation Comment
Reporter 18-JAN-01 S.H. Pilcher U.S. Geological Survey