|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 6120 prospect is on the steep, precipitous southern flank of Peak 6,920 at the head of Sheep Creek. It is at an elevation of 5,750 feet in the NW1/4 sec. 5, T. 25 N., R. 24 W., of the Seward Meridian.|
The Pyrrhotite occurrence consists of several pods of pyrrhotite with minor pyrite, enclosed in banded hornfels and marble adjacent to a small stock of highly altered granodiorite porphyry. The host rocks are thermally altered marble and clastic sediments of the mid-Silurian Terra Cotta Mountains Sandstone, a unit of the Dillinger sub-terrane (Bundtzen and others, 1997).
Pyrrhotite occurs as disseminated grains in veinlets up to 8 centimeters thick, as semi-massive to massive sulfide pods up to 30 centimeters thick, and as clots and crystals up to three centimeters across. Grab samples of pyrrhotite-rich mineralization collected by Anaconda Minerals Company contained up to 0.44 percent nickel and 460 parts per million (ppm) cobalt (Brewer and others, 1992). Selected samples reported by Foley (1987) contain up to 180 ppm nickel, 180 ppm copper, and 180 ppm zinc. Massive pyrrhotite-bearing samples contained 58.00 percent iron.In 2008, the 6120 prospect was one of the prominent deposits in a block of claims that covered more than 70 square miles, known collectively as the BMP project (International Tower Hill Mines, Ltd., (ITH) (2008). Their mapping in 2007 suggests that the mineralization occurs along a fault developed associated with a north-trending anticlinal hinge that extends 8 to the north through several deposits (MG061, MG057, MG052-049), and notable the Dahl prospect (MG053). Twenty samples of skarn collected in outcrop by ITH in 2008 contained an average of 2.3 percent copper, 3.4 grams of gold per ton, 33 grams of silver per ton, 0.16 percent nickel and 0.07 percent cobalt.
|Geologic map unit||(-153.78262157103, 62.2865858898825)|
|Mineral deposit model||Polymetallic replacement? (Cox and Singer, 1986; model 19a?).|
|Mineral deposit model number||19a?|
|Alteration of deposit||None.|
|Workings or exploration||The 6120 occurrence (initially called the Pyrrhotite prospect) was discovered during geologic mapping in 1981 by the Alaska Division of Geological and Geophysical Surveys (Bundtzen, Kline, and Clough, 1982). The prospect was examined by several companies and government agencies through the 1980s and 1990s. In 2008, the 6120 prospect was one of the prominent deposits in a block of claims that covered more than 70 square miles, known collectively as the BMP project (International Tower Hill Mines, Ltd., (2008). They mapped and sampled the deposit in 2007.|
|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|