|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 Marsha prospect is at an elevation of about 4,300 feet, about 3.3 miles west of the mouth of Ann Creek. It is about 0.4 mile north-northwest of the center of section 21, T. 18 S., R. 10 E.|
The Marsha prospect is associated with 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 prospect is just south of the Broxson Gulch thrust fault and is between splays of imbricated thrust faults that juxtapose slivers of dark ultramafic rocks with volcaniclastic rocks of the Slana Spur Foundation. Both are intruded by gabbro dikes up to 30 feet thick.
From the late 1980s into at least the 1990s, the Marsha prospect was examined and sampled by several companies, including Teck Cominco America, Northeast Mining Company, MAN Resources Inc., and Nevada Star Resource Corp. but there are no workings on it. Examined and sampled by the Bureau of Land Management in the early 2000s (Bittenbender and others, 2007).At least three discontinuous lenses and nodules of oxidized chalcopyrite, pyrrhotite, and pentlandite are along the contact of a gabbro dike and serpentinized ultramafic rock. The largest sulfide lens is about 6 feet by 5 feet in area. Samples contained up to 6.25 percent copper, 1,540 parts per million (ppm) nickel, and 1,470 ppm zinc. The mineralization is discontinuous and does not extend far along strike.
|Geologic map unit||(-145.850258902255, 63.3431852079222)|
|Mineral deposit model||Nickel-copper-PGE mineralization in a differentiated mafic-ultramafic complex.|
|Age of mineralization||Genetically related to the emplacement of a Late Triassic mafic-ultramafic complex.|
|Alteration of deposit||The ultramafic rocks are extensively serpentinized.|
|Workings or exploration||From the late 1980s into at least the 1990s, the Marsha prospect was examined and sampled by several companies, including Teck Cominco America, Northeast Mining Company, MAN Resources Inc., and Nevada Star Resource Corp. but there are no workings on it. Examined and sampled by the Bureau of Land Management in the early 2000s (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|