|Quadrangle map, 1:250,000-scale||MH|
|Quadrangle map, 1:63,360-scale||B-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Rainy Breccia prospect is at an elevation of about 5,600 feet, 2.9 miles north of the junction of the North and West Forks of Rainy Creek. It is 0.6 mile south-southwest of the center of section 19, T. 18 S., R. 10 E.|
The Rainy Breccia prospect is near the north margin of the Late Triassic, Rainy Creek ultramafic-mafic complex that intrudes volcanic and sedimentary rocks of the Tetelna Volcanics and the Slana Spur Formations, both of Pennsylvanian and Permian age (Stout, 1976, Nokleberg and others, 1992 [MF]; 1992 [Open-File]; Bittenbender and others, 2007). The complex is up to 5,000 feet thick, dips shallowly north, and can be traced for more than 15 miles. It is mainly serpentinized dunite with subordinate peridotite, pyroxenite, and gabbro. The base of the complex is a layered gabbro as much as 1,500 feet thick.
The prospect was discovered by the American Copper and Nickel Company (ACNC) in 1995 and later examined and sampled by the Bureau of Land Management (Bittenbender and others, 2007). As described by W.T. Ellis (oral communication, 2001), the Rainy Breccia prospect is in breccia that consists of subrounded clasts of dunite in a dark-colored gabbronorite matrix. The unit is several hundred feet long and approximately 50 feet thick. The breccia strikes S65E and dips 75N. The mineralization in the matrix consists of up to 6 percent disseminated pyrrhotite and magnetite, with traces of chalcopyrite and pentlandite as inclusions in the pyrrhotite. A grab sample of the sulfide-bearing breccia contained 0.12 percent nickel, 0.15 percent copper, 0.01 percent cobalt, 26 parts per billion (ppb) palladium, and 25 ppb platinum.Bittenbender and others (2007) examined the area but were not certain that they located the the prospect described by Ellis. They did locate two breccia zones with disseminated sulfides in the immediate area; one with peridotite clasts in a leucogabbro matrix and the other brecciated peridotite. However, their samples had low base- and precious-metal values. The best contained 135 parts per million (ppm) copper, 1,285 ppm nickel, 13.9 ppb platinum, and 16 ppb palladium.
|Geologic map unit||(-145.90245951493, 63.3323838984474)|
|Mineral deposit model||Nickel-copper-PGE mineralization in a differentiated mafic-ultramafic sill.|
|Age of mineralization||Genetically related to the emplacement of a Late Triassic mafic-ultramafic complex.|
|Alteration of deposit||Irregular serpentinized zones occur along the breccia contact.|
|Workings or exploration||The prospect was discovered by the American Copper and Nickel Company (ACNC) in 1995 and was later examined and sampled by the Bureau of Land Management (Bittenbender and others, 2007).|
|Indication of production||None|
Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Foley, J.Y., 1992, Ophiolite and other ultramafic metallogenic provinces in Alaska (west of the 141th meridian): U.S. Geological Survey Open-File Report 92-20-B, 55 p.
Nokleberg, W. J., Aleinikoff, J. N., Dutro, J. T., Lanphere, M. A., Silberling, N. J., Silva, S. R., Smith, T. E., and Turner, D. L., 1992, Map, tables, and summary of fossil and isotopic age data, Mount Hayes Quadrangle, eastern Alaska range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-D, 43 p., 1 sheet, scale 1:250,000.
Nokleberg, W.J., Aleinikoff, J. N., Lange, I. M.; Silva, S. R., Miyaoka, R. T., Schwab, C. E., Zehner, R. E., Bond, G. C., Richter, D. H., Smith, T. E., and Stout, J. H., 1992, Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Open-File Report 92-594, 39 p. 1 sheet, scale 1:250,000.
Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000.
|Reporters||W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS)|
|Last report date||5/13/2012|