Glacier Fork (ARDF #LC008) Au, Cu

Glacier Fork

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Au; Cu
Other commodities	Ag; Zn
Ore minerals	arsenopyrite; chalcopyrite; pyrrhotite; sphalerite
Gangue minerals	garnet

Geographic location

Quadrangle map, 1:250,000-scale	LC
Quadrangle map, 1:63,360-scale	D-1
Latitude	60.857
Longitude	-153.206
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	Occurrence is on a peak surrounded by glaciers in the Neacola Mountains, central portion of the Lake Clark D-1 quadrangle. Locality 5 of Nelson and others (1985). SE1/4NE1/4 sec. 20, T. 9 N., R. 22 W., of the Seward Meridian. Accurate within 450 meters.

Geologic setting

Geologic description Nelson and others (1985) describe a high-grade, iron-poor, garnet-rich skarn deposit that consists of marble interbedded with schist and phyllite and metamorphosed mafic volcanic rocks in a large roof pendant in granitic rocks (Nelson and others, 1983). Mineralization consists of layers and veinlets of massive to disseminated pyrrhotite, chalcopyrite, arsenopyrite, and sphalerite. Nokleberg and others (1987) reported chip samples grading 20 g/t Ag, 0.38 g/t Au, 0.76 percent Cu, 3.4 percent Zn. Similar occurrences include the two unnamed occurrences (ARDF number LC002 and LC010) in the Neacola Mountains. According to Nelson and others (1983, unit MzPzm), some of the metasedimentary rocks may correlate with the Kakhonak Complex of Permian (?), Triassic, and Jurassic age in the Iliamna quadrangle, and some may be graywacke of Jurassic and Cretaceous (?) age that has been metamorphosed by nearby plutonic rocks. Some of the metamorphosed volcanic rocks, especially in roof pendants, are probably part of the volcanic rocks of Tertiary age (Tv).
Geologic map unit	(-153.208248863942, 60.8563698100072)
Mineral deposit model	Cu skarn (Cox and Singer, 1986; model 18b)
Mineral deposit model number	18b
Age of mineralization	Permian (?) through Tertiary (?).
Alteration of deposit	Unknown

Production and reserves

Workings or exploration	Nokleberg and others (1987; 1997) reported chip samples grading 20 g/t Ag, 0.38 g/t Au, 0.76 percent Cu, 3.4 percent Zn.
Indication of production	None
Reserve estimates	No reserves
Production notes	No production
Additional comments Discovered in 1978 by B.L. Reed. Referenced in Nelson and others, 1985, locality 5 as 'B.L. Reed and D.R. Cox, Oral Communication, 1980.' Site is in Lake Clark National Park and Preserve.

References

MRDS Number	A013023
References Nelson, W.H., Carlson, C., and Case, J.E., 1983, Geologic map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-A, 1 sheet, scale 1:250,000. Nelson, W.H., King, H.D., Case, J.E., Tripp, R.B., Crim, W.D., and Cooley, E.F., 1985, Mineral resource map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-B, 1 sheet, scale 1:250,000. 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. Nokleberg, W.J., Bundtzen, T.K., Dawson, K.M., Eremin, R.A., Goryachev, N.A., Koch, R.D., Ratkin, V.V, Rozenblum, I.S., Shpikerman, V.I., Frolov, Y.F., Gorodinsky, M.E., Melnikov, V.D., Diggles, M.F., Ognyanov, N.V., Petrachenko, E.D., Petrochenko, R.I., Pozdeev, A.I., Ross, K.V., Wood, D.H., Grybeck, D., Khanchuck, A.I., Kovbas, L.I., Nekrasov, I.Y., and Sidorov, A.A., 1996, Significant metalliferous and selected non-metalliferous lode mineral deposits and placer districts, and for metallogenesis of the Russian Far East, Alaska, and the Canadian Cordillera: U.S. Geological Survey Open-File Report 96-513-B, 385 p.; U.S. Geological Survey Open-File Report 96-513-B, 385 p. (CD-ROM format).
Reporters	M.L. Miller (USGS); D.P. Bickerstaff (USGS)
Last report date	6/15/1998