Badnews

Site Name

Primary: Badnews

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Commodity

Primary: Zinc
Primary: Gold
Primary: Copper
Primary: Silver
Secondary: Cadmium
Secondary: Cobalt
Secondary: Lead

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Location

State: Alaska
District: McGrath

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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: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Skarn Zn-Pb

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Strong secondary biotite (potassic) alteration in skarn.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Sphalerite
Ore: Pyrrhotite
Ore: Pyrite
Ore: Galena
Ore: Chalcopyrite
Gangue: Quartz
Gangue: Garnet
Gangue: Epidote
Gangue: Calcite

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Comments

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = Foley, 1987

Comment (Deposit): Model Name = Low temperature lead-zinc skarn (Cox and Singer, 1986; model 18c).

Comment (Deposit): Other Comments = Similar to Tin Creek-Midway (MG043), and Rat Fork-Headwall (MG059) prospects. The Badnews skarn prospect contains more gold than any other prospect or occurrence in the Farewell Mineral Belt.

Comment (Geology): Geologic Description = The Badnews polymetallic prospect is a Cu-Pb-Zn-Ag-Au (Co-Pb) skarn deposit in tightly folded limestone, siltstone, and argillite of the mid-Silurian Terra Cotta Mountains Sandstone, a unit of the Dillinger subterrane (Bundtzen, Harris, and Gilbert, 1997). The limestone layers have been preferentially replaced by skarn minerals and locally sulfides; clastic rocks have been transformed into purple-green hornfels. Central to the prospect area is a granodiorite porphyry stock with apophyses and numerous dikes intruding a large aureole of hornfelsed sedimentary rocks (Bundtzen, Harris, and Gilbert, 1997). Several east-west trending, high-angle, granodiorite dikes cut the limestone; the dikes are apparently pathways for hydrothermal-skarn mineralization. A post skarn breccia occurs at the contact of one granodiorite dike. . Principle sulfide minerals include; chalcopyrite, pyrrhotite, sphalerite, and a trace of galena. Pyrrhotite is the dominant sulfide in practically all mineralized skarn zones. Skarn gangue includes abundant recrystallized calcite and red garnet, with minor epidote and quartz. Massive sulfide pods and mantos ranging up to 10 meters thick can be traced laterally for several hundred meters (Brewer and others, 1992). Individual sulfide zones reach a maximum thickness of 0.7 meters within skarn zones up to 2 meters wide. Sphalerite is most abundant in epidote-garnet-rich rock whereas chalcopyrite and pyrrhotite are most abundant in lighter calcite-garnet rock (Foley, 1987). In sulfide skarns where chalcopyrite and sphalerite dominate, 23 grab samples averaged 3.7 percent zinc and 0.4 percent copper (Brewer and others, 1992). Selected samples from zinc-rich areas also contain up to 1,740 ppm cadmium. Overall gold values are more anomalous in the Badnews skarn prospect than in any other area of the Farewell Mineral Belt, with assays of up to 11.2 grams/tonne gold and 143.1 grams/tonne silver noted (Brewer and others, 1992). An average gold value of 490 ppb gold was obtained from numerous other sulfide-bearing grab samples at the prospect. Two grab samples of sulfide-bearing skarn collected by Foley (1987) contained maximum values of 9.20 percent zinc, 93 ppm lead, 0.44 percent copper, 290 ppm cobalt, and 16.6 grams/tonne silver.

Comment (Workings): Workings / Exploration = The Badnews polymetallic prospect was named by Roger Burleigh during mineral investigations conducted in 1979 by Placid Oil Company. Only surface sampling has taken place at the site, mainly by Anaconda Minerals and the U.S. Bureau of Mines. Where sphalerite and chalcopyrite dominate, 23 grab samples average 3.7 percent zinc and 0.4 percent copper (Brewer and others, 1992). Overall gold values are more anomalous in the Badnews skarn prospect than in any other area of the Farewell mineral belt; with assays of up to 11.2 grams/tonne gold and 143.1 grams/tonne silver noted (Brewer and others, 1992). Two samples of sulfide-bearing skarn collected by Foley (1987) contained up to 9.20 percent zinc, 93 ppm lead, 0.44 percent copper, 290 ppm cobalt, and 16.6 grams/tonne silver.

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References

Reference (Deposit): Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 pages, one sheet, scale 1:125,000.

Reference (Deposit): Brewer, N.H., Puchner, C.C., and Gemuts, I., 1992, Farewell district, southwest Alaska Range: North Pacific Mining Company prospectus report, 21 pages

Reference (Deposit): Foley, J.Y., 1987, Reconnaissance strategic and critical mineral investigations in the McGrath A-3 and B-2 quadrangles, southwest Alaska: U.S. Bureau of Mines Field Report, 26 pages.

Reference (Deposit): Bundtzen, T.K., Kline, J.T., and Clough, J.G., 1982, Preliminary geologic map of the McGrath B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File report 149, 22 pages, one sheet, scale 1:63,360.

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