Prospect, Undetermined

Commodities and mineralogy

Main commodities Cu
Other commodities Barite
Ore minerals barite; chalcopyrite; pyrite
Gangue minerals carbonate; quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-6
Latitude 55.164
Longitude -131.784
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Friday prospect is near tidewater, about midway along the southeast shore of Nehenta Bay. The site is in sec 25, T. 77 S., R. 90 E., of the Copper River Meridian. It corresponds to loc. 122 in Elliott and others (1978). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

Southern Gravina Island is underlain by an assemblage of undivided Silurian or Ordovician metamorphosed bedded and intrusive rocks; a stock and associated dikes of Silurian trondhjemite that cuts the metamorphic assemblage; and a sequence of Upper Triassic carbonate, clastic, rhyolitic, and basaltic strata that unconformably overlies the older rocks (Berg, 1973, 1982; Berg and others, 1988). The rocks are complexly folded and are cut by high-angle faults and by low-angle thrust faults. In many places, the Triassic rhyolite and the rocks beneath it are permeated by microscopic particles of hydrothermal hematite, giving them a pink, purple, or red hue (Berg, 1973, p. 14).
The Friday prospect was probably staked for copper in the early 1900s (U. S. Bureau of Mines, 1977); it was mapped, and the prospect briefly examined, by the U.S. Geological Survey in 1969 (Elliott and others, 1978). Elliott and others describe the deposit as pyrite- and chalcopyrite-bearing quartz-carbonate-barite? veins in breccia zones in strongly iron-stained metamorphosed volcanic, sedimentary and intrusive country rocks. Berg (1973, pl. 1) maps the rocks at and near this prospect as Triassic basal conglomerate containing clasts of the underlying trondhjemite and metamorphic assemblage. The mineralized breccia zones probably are hosted by this conglomerate, rather than by the metamorphic unit described by Elliott and others. The country rocks at the Friday prospect are cut by a high-angle fault that strikes NE, parallel to the SE shoreline of Nehenta Bay (Berg, 1973, pl. 1). Several occurrences of barite-bearing fissure veins are in Triassic sedimentary rocks on the islands at the mouth of Nehenta Bay. The characteristics and setting of these deposits suggest that they are polymetallic veins of Late Triassic or younger age. Workings visible in 1969 were a few small pits and short tunnels.
Geologic map unit (-131.78567737825, 55.1636535340095)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Late Triassic or younger.
Alteration of deposit Locally conspicuous iron staining.

Production and reserves

Workings or exploration Workings visible in 1969 were a few small pits and short tunnels.
Indication of production Undetermined