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Unnamed (west of Anderson Mountain)

Prospect in Alaska, United States with commodities Silver, Copper, Lead, Zinc
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Geologic information

Identification information

Deposit ID 10307537
Record type Site
Current site name Unnamed (west of Anderson Mountain)

Geographic coordinates

Geographic coordinates: -147.95284, 63.79963 (WGS84)
Relative position The prospect is located about 0.5 mile west of the summit of Anderson Mountain at an elevation of 4,500 to 5,500 feet. It is in sec. 9, T. 13 S., R. 2 W., of the Fairbanks Meridian. The location is accurate to within one mile. This is locality 12 of Cox and others (1989).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Copper Primary
Lead Primary
Zinc Primary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Enargite Ore
Galena Ore
Sphalerite Ore
Barite Gangue
Calcite Gangue
Chlorite Gangue
Quartz Gangue
Sericite Gangue
Siderite Gangue

Alteration

  • (Local) Absence of footwall alteration and stringer mineralization suggests off-vent deposition.

Mineral occurrence model information

Model code 184
USGS model code 28a
Deposit model name Massive sulfide, kuroko
Mark3 model number 93

Host and associated rocks

  • Host or associated Host
    Stratigraphic age (youngest) Late Devonian

Nearby scientific data

(1) -147.95284, 63.79963
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Comments on the geologic information

  • Geologic Description = The prospect is in the Upper Devonian(?) felsic metavolcanic schist and phyllite, often containing relict phenocrysts of quartz, orthoclase, and plagioclase (Wilson and others, 1998). The deposit consists of massive layers of chalcopyrite, galena, sphalerite, enargite, and arsenopyrite in gangue of quartz, sericite, chlorite, calcite, barite, and siderite. The sulfide beds appear to lie on an irregular paleosurface on the footwall, with domal sulfide accumulations at the tops of layers (Nokleberg and others, 1994). The Hines Creek fault, a major structure that is responsible for much structural complexity at Anderson Mountain, is two miles south of the prospect. Numerous high-angle faults displace the sulfide layers, and folding makes tracing the layers a challenge. The discovery drill hole in 1976 intersected a massive sulfide zone that measured 1.7 meters thick and assayed 1.2% copper, 2% lead, 8.5% zinc and 61.4 grams of silver per ton (Schuster, 1998). Surface grab samples reportedly contain 14% combined lead and zinc, 2.5% copper and 274 grams of silver per ton. Nokleberg and others (1994) report copper grades varying from 0.5 to 19%, lead grades up to 5%, up to 22% zinc and up to 170 grams of silver per ton.
  • Age = Mineralization was probably syngenetic with the Upper Devonian host rocks.

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Active

Mining district

District name Bonnifield

Comments on the workings information

  • Workings / Exploration = Geophysical and geochemical surveys have defined a potential zone of volcanogenic massive sulfide mineralization stretching over a strike length of 1373 meters. There has been about 2500 meters of drilling at the prospect (Robertson, 1998). The discovery drill hole in 1976 intersected a massive sulfide zone that measured 1.7 meters thick and assayed 1.2% copper, 2% lead, 8.5% zinc and 61.4 grams of silver per ton (Schuster, 1998). Surface grab samples reportedly contain 14% combined lead and zinc, 2.5% copper and 274 grams of silver per ton. Nokleberg and others (1994) report copper grades varying from 0.5 to 19%, lead grades up to 5%, up to 22% zinc and up to 170 grams of silver per ton.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF HE096

Bibliographic references

  • 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

    Cox, D.P., Light, T.D., Csejtey, Bela, Jr., and Campbell, D.L., 1989, Mineral resource assessment map of the Healy quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map, MF-2058-A, scale 1:250,000.

  • Deposit

    Nokleberg, W.J., and others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society of America: The Geology of North America, v. G1, p. 855-904 and v. G1, Plate 11, scale 1:2,500,000.

  • Deposit

    Robertson, R, 1998, Grayd hits massive sulphide: The Northern Miner, v. 84, no. 17, p. 3.

  • Deposit

    Schuster, T., 1998, Grayd advances Alaskan properties: The Northern Miner, v. 84, no. 18, p. 2.

  • Deposit

    Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of central (interior) Alaska: U.S. Geological Survey Open-File Report 98-133, 17 p., 2 sheetsm, scale 1:500,000.

Comments on the references

  • Primary Reference = Nokleberg and others, 1994

General comments

Subject category Comment text
Deposit Model Name = Kuroko massive sulfide (Cox and Singer, 1986; model 28a)
Deposit Other Comments = High geochemical values of arsenic, antimony, mercury, and tungsten may be derived from older schist basement. Anderson Mountain is significantly different from prospects in the Totatlanika Schist belt to the north (e.g. HE122) in having higher Cu content.

Reporter information

Type Date Name Affiliation Comment
Reporter 07-APR-00 N. Van Wyck Stevens Exploration Management Corporation