|Quadrangle map, 1:250,000-scale||MG|
|Quadrangle map, 1:63,360-scale||A-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Chip-Loy deposit is on a steep valley wall of what is locally called Straight Creek, one of the headwater tributaries of the Middle Fork of the Kuskokwim River. It is between about 2,900 feet to 4,000 feet in elevation, about 0.3 mile southeast of the center of section 15, T. 24 N., R. 28 W., of the Seward Meridian. The location is accurate.|
According to Herreid (1968), Foley (1987), and Foley and others (1997), the Chip-Loy deposit consists of an irregular, steeply dipping layer of massive to disseminated, nickelian pyrrhotite and other sulfides in an elongate, composite, diabase intrusion. Herreid (1968) describes the diabase, which ranges from gabbro to diorite, as a pipe in plan view, but Smith and Albanese (1985) describe it as a dike. The diabase trends in a northeast direction and varies from 40 meters to 260 meters wide; cliff walls prevent accurate investigations of the intrusion's true dimensions. The composite diabase intrusion cuts mid-Silurian Terra Cotta Mountains Sandstone, a formation of the Dillinger subterrane of Lower Paleozoic age. (Bundtzen, Harris, and Gilbert, 1997). Gilbert and others (1988) assign an early Tertiary age to the mineralized diabase intrusion.
The Chip-Loy deposit contains disseminated to massive sulfides, mainly pyrrhotite and chalcopyrite, with minor cubanite and sphalerite, and trace galena, bravoite, violarite, tetradymite (Bi2Te2S), and undetermined Co-Ni-Fe arsenides (Bart Cannon, written communication, 1998). The sulfides are intergrown with ilmenite and other rock-forming minerals such as plagioclase and olivine. The northeast trending, sulfide-bearing zone is in the diabase about 10 to 30 meters from the contact with sandstone and shale. The zone is about 335 meters long and 10 to 15 meters wide but is quite irregular along strike. Herreid (1968) estimated that the Chip-Loy deposit contains an inferred reserve of about 150,000 tonnes of disseminated and massive sulfide mineralization. Smith and Albanese (1985) suggested a larger reserve than Herreid; they estimate 0.15 to 1.25 million tonnes of sulfide mineralization.
Chip-channel samples from the Chip-Loy deposit contained up to 3.30 percent nickel, 0.25 percent cobalt, 2.10 percent copper, 12.1 grams of silver per tonne, and 43.2 percent iron (Smith and Albanese, 1985; Bundtzen and others, 1982). A single sample of massive sulfide mineralization contained 3.0 grams of gold per tonne (Foley, 1987; Gilbert and others, 1988). Tetradymite is in the interstices of the rock-forming silicates. A 12-meter-long chip-channel sample across the deposit contained 0.28 percent copper, 2.6 grams of silver per tonne, 444 parts per million (ppm) cobalt, 0.70 percent nickel, and 17.82 percent iron (Smith and Albanese, 1985; Gilbert and others, 1988). Pyrrhotite from selected samples averaged 0.4 percent cobalt and 1.5 percent nickel (Bart Cannon, written communication, 1998). About 50 percent of the nickel and cobalt is in pyrrhotite; the remainder is in pentlandite and other nickel and cobalt minerals.Brozdowski and Taylor (2009) reported on recent work by Nycon Resources Inc. as part of their exploration on a large block of claims. They drilled the prospect and flew two airborne geophysical surveys over it that covered about 195 square kilometers. Brozdowski and Taylor describe the deposit as a highly-contaminated Early Tertiary gabbro to diorite dike. Grab samples contained up to 2.7 percent nickel, 0.4 percent copper, and 20 parts per billion platinum and palladium. The aerial geophysical data suggest that the Chip-Loy prospect is part of a belt of similar deposits that includes the nearby Roberts prospect (MG030).
|Geologic map unit||(-154.385635648468, 62.1657657613647)|
|Mineral deposit model||Gabbroic Ni-Cu (Cox and Singer, 1986; model 7a).|
|Mineral deposit model number||7a|
|Age of mineralization||Little evidence for age. Thought to be early Tertiary by Gilbert and others (1988) and Brozdowski and Taylor (2009); however, the nearby Roberts deposit (MG030) possibly is Late Triassic.|
|Alteration of deposit||Slight oxidation of massive sulfides.|
|Workings or exploration||The Chip-Loy deposit was discovered and staked by prospectors Ed Chipp and Robert Loy in the early 1960s. Since then numerous geologists from industry and government have visited and sampled it. In 2009, the prospect was explored and drilled by Nycon Resources, Inc. as part of their study of similar deposits on a large block of claims that covered this prospect.|
|Indication of production||None|
|Reserve estimates||Herreid (1968), who provides the only detailed geologic map of the Chip-Loy deposit, estimated approximately 150,000 tonnes of disseminated-to- massive sulfide mineralization. Smith and Albanese (1985) estimated that that the deposit contains 0.15 and 1.25 million tonnes of disseminated to massive mineralization.|
Brozdowski, R.A., and Taylor, S.R., 2009, Magmatic Ni-Cu-PGE in mafic-ultramafic intrusive conduits to a Triassic flood basalt province, Nycon Resource's Farewell District project, southwestern Alaska: Abstracts, Alaska Minerals Association 2009 Annual Convention, p. 17-18 (posted on the Internet at www.alaskaminers.org/abstracts2009.pdf)
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.
Cobb, E.H., 1972, Metallic mineral resources map of the McGrath quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-379, 1 sheet, 1:250,000 scale.
Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-485, 101 p.
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.
Foley, J.Y., Light, T.D., Nelson, S.W., and Harris, R.A., 1997, Mineral occurrences associated with mafic-ultramafic and related alkaline complexes in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 396-449.
Gilbert, W.G., Solie, D.N., and Kline, J.T., 1988, Geologic map of the McGrath A-3 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 92, 2 sheets, scale 1:63,360.
Herreid, G.H., 1968, Geological and geochemical investigations southwest of Farewell, Alaska: Alaska Division of Mines and Geology Geologic Report 26, 24 p., 1 sheet, scale 1:75,000.
Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.
|Reporters||T.K. Bundtzen (Pacific Rim Geological Consulting); D.J. Grybeck (Contractor, U.S. Geological Survey)|
|Last report date||4/2/2010|