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.


MRDS Number A013023


Reporters M.L. Miller (USGS); D.P. Bickerstaff (USGS)
Last report date 6/15/1998