|Quadrangle map, 1:250,000-scale||MG|
|Quadrangle map, 1:63,360-scale||B-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Badnews Prospect is on a steep, precipitous, north-facing slope of Peak 6,920; it is at an elevation of about 5,700 feet in the SW1/4 sec. 32, T. 26 N., R. 24 W., of the Seward Meridian. The location is from Foley (1987).|
The deposit at the Badnews prospect is a Cu-Pb-Zn-Ag-Au (Co-Pb) skarn in tightly folded limestone, siltstone, and argillite of the mid-Silurian Terra Cotta Mountains Sandstone, a unit of the Dillinger sub-terrane (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. The center of the prospect is a granodiorite porphyry stock with apophyses and numerous dikes that intrude a large aureole of hornfelsed sedimentary rocks (Bundtzen, Harris, and Gilbert, 1997). Several east-trending, high-angle, granodiorite dikes cut the limestone; the dikes are apparently pathways for the fluids that deposited the mineralization and formed the skarn. A post-skarn breccia occurs at the contact of one granodiorite dike.
The main ore minerals are chalcopyrite, pyrrhotite, sphalerite, and a trace of galena. Pyrrhotite is the dominant sulfide in practically all the mineralized skarn zones. The skarn consists of abundant recrystallized calcite and red garnet, with minor epidote and quartz. Massive sulfide pods and mantos 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 in skarn zones that are up to 2 meters wide. Sphalerite is most abundant in epidote-garnet-rich skarn, whereas chalcopyrite and pyrrhotite are most abundant in calcite-garnet skarn (Foley, 1987).
Twenty-three grab samples from skarns where chalcopyrite and sphalerite dominate contained an average of 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 parts per million (ppm) cadmium. The gold content of the Badnews skarn is higher than in any other deposit of the Farewell Mineral Belt; select samples contain up to 11.2 grams of gold per tonne and 143.1 grams of silver per tonne (Brewer and others, 1992). The average gold content of numerous grab samples of the mineralized skarn was 490 parts per billion. Two grab 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 of silver per tonne.In 2008, this prospect was one of several in a block of claims that covered more than 70 square miles, known collectively as the BMP project (International Tower Hill Mines, Ltd., (2008).
|Geologic map unit||(-153.770621854888, 62.2958865368446)|
|Mineral deposit model||Low temperature lead-zinc skarn (Cox and Singer, 1986; model 18c).|
|Mineral deposit model number||18c|
|Alteration of deposit||Strong secondary biotite (potassic) alteration in skarn.|
|Workings or 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. As of 2008, the prospect was within a large block of claims called the BMP project by International Tower Hill MIne, Ltd. (2008).|
|Indication of production||None|
Brewer, N.H., Puchner, C.C., and Gemuts, I., 1992, Farewell district, southwest Alaska Range: North Pacific Mining Company prospectus report, 21 p.
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 p., 1 sheet, scale 1:125,000.
Bundtzen, T.K., Kline, J.T., and Clough, J.G., 1982, Preliminary geology of the McGrath B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File report 149, 22 p., 1 sheet, scale 1:40,000.
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 p.
International Tower Hills Mines, Ltd., 2008, BMP: http://www.ithmines.com/s/BMP.asp (as of April 30, 2008).
|Reporters||T.K. Bundtzen (Pacific Rim Geological Consulting); D.J. Grybeck (Port Ludlow, WA)|
|Last report date||6/5/2008|