Unnamed (north of confluence of Chickamin River and South Fork)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals chalcopyrite

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale D-3
Latitude 55.909
Longitude -130.724
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 1300 feet in the walls of a steep avalanche gully west of the Chickamin River, approximately 2.5 miles north of its confluence with the South Fork. The site is in section 5, T. 69 S., R. 96 E., of the Copper River Meridian. It corresponds to area M-3 in Berg and others (1977), and to loc. 18 in Elliott and others (1978). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this occurrence consist chiefly of rusty-weathering pelitic paragneiss that forms roof pendants, screens, and inclusions in Tertiary or Cretaceous foliated granodiorite and quartz diorite of the Coast Range batholith (Berg and others, 1977, p. 126; Berg and others, 1988). The paragneiss probably represents marine argillaceous and clastic strata that underwent high-grade regional metamorphism in Cretaceous or Tertiary time. The premetamorphic age of the strata is uncertain, but they probably are mainly Paleozoic and may be as old as Precambrian (Berg and others, 1988, p. 26; Gehrels and others, 1990; Crawford and others, 2000).
The occurrence consists of a 150-foot-thick zone of rusty-weathering paragneiss that strikes about N10W and can be traced in outcrop for about a mile northwest of Chickamin River (Berg, 1977, p. 126 and pl. 2). The zone probably is the northwest extension of a similar rusty zone on the other side of the river (KC019). The paragneiss locally contains a little pyrrhotite and a trace of chalcopyrite. Eight chip samples across about 125 feet of section perpendicular to the foliation assayed as much as 340 ppm Cu and 2 ppm Ag (Berg and others, 1977, p. 126 and fig. 35).
Geologic map unit (-130.725706706978, 55.9086557169598)
Mineral deposit model Disseminated base-metal sulfides in rusty-weathering paragneiss
Alteration of deposit Conspicuous iron-staining.

Production and reserves

Workings or exploration Eight chip samples across about 125 feet of section perpendicular to the foliation assayed as much as 340 ppm Cu and 2 ppm Ag (Berg and others, 1977, p. 126 and fig. 35).
Indication of production None

Additional comments

Site is in Misty Fiords National Monument Wilderness.

References