|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 Sheep Creek-1 occurrence is in the main tributary valley of Sheep Creek, about 2.0 kilometers upstream from the junction of the main tributary and the Smith Lake fork. It is at an elevation of about 2,800 feet in the SW1/4 sec. 18, T. 26 N., R. 24 W., of the Seward Meridian.|
The Sheep Creek-1 occurrence is a discontinuous zone of metal-bearing, sulfur-rich shale and siltstone of the Lower Ordovician to Lower Silurian Post River Formation, a unit of the Dillinger sub-terrane (Bundtzen, Harris, and Gilbert, 1997). The shale-hosted mineralization contains graptolites that correspond to the Monograptus spiralis zone of Lower Silurian age. The mineralized zones occur in distinctive areas where a bright yellow sulfur staining seeps out of pyrite-rich lamina in the black shale. Within the sulfur-rich zones, disseminated pyrite and sphalerite occur in bands 2 to 4 centimeter thick.
Bundtzen, Harris, and Gilbert (1997) regard the Sheep Creek-1 occurrence as a sedimentary-exhalative lead-zinc deposit; however, it may be an epigenetic occurrence related to nearby plutons. Random chip samples reported by Bundtzen, Kline, and Clough (1982) and Bundtzen, Harris, and Gilbert (1997) from four stratiform horizons contained an average of 600 parts per million (ppm) lead, 1,700 ppm zinc, 1,000 ppm vanadium, and 2.7 grams of silver per tonne. Smith and Albanese (1985) reported a single sample from the Sheep Creek-1 occurrence that contained 720 ppm lead, 37.1 grams of silver per tonne, and 472 ppm antimony.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||(-153.804021720906, 62.3412875462036)|
|Mineral deposit model||Sedimentary exhalative Pb-Zn? deposit (Cox and Singer, 1986; model 31a).|
|Mineral deposit model number||31a?|
|Age of mineralization||Inferred to be Lower Silurian based on graptolite collected at the prospect.|
|Alteration of deposit||Strong sulfurous alteration.|
|Workings or exploration||First recognized in 1981 (Bundtzen, Kline, and Clough, 1982). The prospect was subsequently examined by industry and government. 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|
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.
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|