|Main commodities||Cu; Ni; Pd; Pt|
|Ore minerals||chalcopyrite; magnetite; malachite; pentlandite; pyrrhotite|
|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 North Rainy prospect is at an elevation of about 4,200 feet on the east side of the North Fork Rainy Creek about 3.8 miles north-northwest of its mouth. It is about 0.2 mile northeast of the center of section 24, T. 18 S., R. 9 E. The location is accurate.|
The North Rainy prospect is in the Late Triassic, Rainy ultramafic-mafic complex that intrudes the Slana Spur Formation of Pennsylvanian and Permian age. The Rainy complex is up to 5,000 feet thick, dips shallowly north and is mainly serpentinized dunite with subordinate peridotite, pyroxenite, and gabbro (Nokleberg and others, 1992 [Open-File]; Nokleberg and others, 1992 [MF]; Bittenbender and others, 2007). In this area, the base of the complex is a layered gabbro as much as 1,500 feet thick.
The rocks at this prospect are variably serpentinized dunite near fine-grained gabbro. Near the hanging wall contact of the complex, there is a well-developed breccia zone at a dunite-gabbro contact that is locally mineralized. The breccia consists of angular dunite clasts of various sizes and at least one large inclusion of hornfelsed sedimentary rocks in a fine-grained gabbro matrix.
From 1995 to 1999, the area was explored by American Copper and Nickel Company (ACNC) working with Fort Knox Gold Resources, Inc. in their regional search for copper-nickel-PGE mineralization. Their work in the area included rock sampling, and airborne and ground geophysical surveys W.T. Ellis, oral communication, 2001). They found the North Rainy prospect in 1998 and carried out a large-loop geophysical survey. over it. There were active claims on the prospect to at least 2002. It was examined and sampled by the Bureau of Land Management in the early 2000s.
The mineralization consists of 2 to 4 percent sulfides, mainly pyrrhotite, with chalcopyrite, and pentlandite (?), disseminated in gabbro, (W.T. Ellis, oral communication, 2001). Float of sulfide-bearing dunite, gossan, and copper-stained serpentinite occur in a few places along the breccia contact. Rock samples contained as much as 0.18 percent nickel, 0.63 percent copper, 0.02 percent cobalt, 76 parts per billion (ppb) palladium, and 80 ppb platinum.Bittenbender and others (2007) examined and sampled the prospect. Their best sample was dunite that contained 74 ppb platinum, 62 ppb palladium, 29 ppb gold, and 2,590 ppm nickel. They also identified: 1) lenses of massive to semi-massive sulfides, mainly pyrite or pyrrhotite and chalcopyrite, and 2) mineralized silica-flooded fault zones in an area of about 150 square feet in hornfelsed sedimentary rocks at the contact of the complex. Samples of the massive sulfides contained up to 158 ppb gold and 1.04 percent copper. Samples from the mineralized fault zones contained up to 445 ppb gold, 25 parts per million (ppm) silver, 2.08 percent copper, and 4,070 ppm lead.
|Geologic map unit||(-145.935561630079, 63.3415835338569)|
|Mineral deposit model||Nickel-copper-PGE mineralization in a differentiated mafic-ultramafic complex; massive sulfides and mineralized veins near the contact of the complex.|
|Age of mineralization||Genetically related to the emplacement of a Late Triassic mafic-ultramafic complex.|
|Alteration of deposit||Irregular serpentinization; oxidization of iron and copper minerals.|
|Workings or exploration||From 1995 to 1999, the area was explored by American Copper and Nickel Company (ACNC) working with Fort Knox Gold Resources, Inc. in their regional search for copper-nickel-PGE mineralization. Their work in the area included rock sampling, and airborne and ground geophysical surveys W.T. Ellis, oral communication, 2001). They found the North Rainy prospect in 1998 and carried out a large-loop geophysical survey. over it. There were active claims on the prospect to at least 2002. It was examined and sampled by the Bureau of Land Management in the early 2000s.|
|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.
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|