Unnamed (southwest of Monsoon Lake)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu
Ore minerals bornite; chalcocite; chalcopyrite; malachite

Geographic location

Quadrangle map, 1:250,000-scale GU
Quadrangle map, 1:63,360-scale D-6
Latitude 62.779
Longitude -146.688
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is near the east end of a six-mile-long, east-trending ridge about 7 to 9 miles south of the Maclaren River. The occurrence is about 4 miles south-southwest of the center of Monsoon Lake. It is in the SE1/4NE1/4, section 34, T. 12 N., R. 8 W., Copper River Meridian, and is located accurately within 1000 feet.

Geologic setting

Geologic description

This occurrence is near the east end of the so-called 'KFC anomalous zone', an elongated east-west zone about 10 miles long which includes the KFC prospect (GU001). This occurrence consists of rubble crop and is coincident with highly anomalous stream sediment values for copper (101-570 ppm ) reported by Castle and Degenhart (1978, figure 6) near the east end of the KFC anomalous zone. Bedrock is mainly composed of schistose basalt and andesite of the Pennsylvanian to Permian, Tetelna Formation. Work to the east of the area (Arehart, 1982) found numerous occurrences of: 1) veinlets and disseminations of bornite, chalcocite, and chalcopyrite; 2) local copper staining in epidotized volcanics; and 3) the Platypus Mountain prospect (GU003), which occurs in a felsic horizon in the volcanics.
Geologic map unit (-146.690231968753, 62.7785560998858)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986, model 24a)
Mineral deposit model number 24a
Age of mineralization Diagenetic or epigenetic remobilization of copper and associated metals in volcanic host rocks of Pennsylvanian to Permian age. Remobilization of copper may have occurred during greenschist metamorphism in the Jurassic(?).

Production and reserves

Workings or exploration The area was prospected on behalf of the Ahtna Native Regional Corporation in 1977 (Castle and Degenhart, 1978). An area immediately to the east was prospected by Noranda Inc. (Arehart, 1982). The exploration was only in reconnaissance.
Indication of production None

Additional comments

It is likely that detailed prospecting will find numerous, additional small occurrence of copper sulfide minerals in metamorphosed andesite and basalt in the area. Additional information can be obtained from Ahtna Minerals in Anchorage, Alaska.


MRDS Number 10307473


Arehart, G.B., 1982, Reconnaissance geology/geochemistry of the Alphabet Hills, Gulkana quadrangle, Alaska: Noranda Exploration, 4 p., maps and appendices. (Report held by Ahtna Minerals Co., Anchorage, Alaska).
Castle, B., and Degenhart, C., 1978, Lichen Greenstone Belt, v. 9 of 1977 Annual Progress Report, Ahtna Project: WGM, Inc., 22 p., maps and appendices. (Report held by Ahtna Minerals Co., Anchorage, Alaska).
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (U.S. Geological Survey)
Last report date 12/20/2000