Chill

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Sn; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale LH
Quadrangle map, 1:63,360-scale B-1
Latitude 61.4831
Longitude -153.0499
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect area is in the eastern headwaters of a large, east tributary to the Chilligan River. The map site is at an elevation of about 4,200 feet at the toe of glacial moraine that covers much of the headwater drainage. It is in the NW 1/4 section 16, T 16 N, R 21 W, of the Seward Meridian. This is locality 16 of Cobb (1972 [MF 412]; 1976 [OF 76-485]) and localities 27 and 28 of Gamble and others (1989). The location is probably accurate to within one-half mile.

Geologic setting

Geologic description

Reed and Elliott (1970) reported several types of mineralization in this area, including: (1) tourmaline-chalcopyrite veins and fracture coatings in and near the contact zone between Tertiary monzonite-granite and country rock sandstone, (2) pyrite-arsenopyrite-chalcopyrite-galena-sphalerite veins in a fault zone that cuts granite, and (3) replacement of limestone by pyrite, pyrrhotite, as much as 5 percent chalcopyrite, and traces of galena. Mineralized float in the area includes (1) mafic rock with 30 percent chalcopyrite and pyrite, (2) tourmaline-quartz rock with 20 percent disseminated arsenopyrite, pyrite, and chalcopyrite, and (3) altered felsic rock with 3 percent disseminated pyrite and galena and limonite and malachite along fractures (Cobb and Reed, 1981). Samples of mineralized bedrock and float contained anomalous silver, copper, lead, tin, zinc, and traces of gold. The Chill claim group that was once located in this area covered a porphyry-type copper deposit and various sulfide-bearing veins. Samples from the general area contained up to 2.8 percent copper, 200 ppm silver, 25 ppm molybdenum, 3,250 ppm lead, 1,350 ppm zinc, and 0.2 ppm gold (Reed and Elliott, 1970; Cobb and Reed, 1981; Gamble and others, 1989). The country rocks are probably Mesozoic sedimentary rocks (Nokleberg and others, 1994) and the Tertiary granitic rocks are part of the Alaska-Aleutian Range batholith (Reed and Lanphere, 1973).
Geologic map unit (-153.052091275571, 61.4824830036329)
Mineral deposit model Polymetallic veins and porphyry Cu (Cox and Singer, 1986, models 22c and 17)
Mineral deposit model number 17, 22c
Age of mineralization Tertiary. Mineralization crosscuts Tertiary intrusive rocks or nearby, thermally metamorphosed sedimentary rocks.
Alteration of deposit Quartz-tourmaline veining and sulfide-rich replacement.

Production and reserves

Workings or exploration Reconnaissance surface observation and sampling has been completed in this area (Reed and Elliott, 1970).
Indication of production None

Additional comments

This occurrence is within Lake Clark National Preserve.

References

MRDS Number A013073

References

Nokleberg, W.J., and (seven) others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol.. G1, p. 855-904, Plate 11, scale 1:2,500,000.
Reed, B.L., and Lanphere, M.A., 1973, Alaska-Aleutian Range batholith--Geochronology, chemistry, and relation to circum-Pacific plutonism: Geological Society of America Bulletin, v. 84, no. 8, p. 2583-2610.
Reporters Travis L. Hudson and Madelyn A. Millholland
Last report date 6/10/2001