Unnamed (near Hemlock Bay)

Occurrences, Undetermined

Commodities and mineralogy

Main commodities Ag; barite; Cu; Pb; Zn
Ore minerals barite; galena; pyrite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.169
Longitude -131.571
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents six occurrences: five along a mile-long section of the south shore of the peninsula between Sylburn Harbor and Port Chester, and one on the north shore of Hemlock Island. The ones on the peninsula are 1.0-2.0 miles east-southeast of Driest Point. The occurrences are in sections 28 and 29, T. 77 S., R. 92 E., of the Copper River Meridian. The map site is at the approximate midpoint of this roughly E-W line of occurrences. The site corresponds to loc. 24a-f in Karl (1992). The location is accurate within about 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site include recrystallized, Upper Triassic carbonate and clastic rocks, rhyolite, and basalt; Silurian trondhjemite; and greenstone derived from undivided Silurian and Ordovician volcanic, sedimentary, and intrusive rocks (Berg, 1972 [I 684]; Berg and others, 1988; Karl, 1992). The rocks are folded and locally intensely sheared, sericitized, and permeated with hydrothermal hematite. The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.
The occurrences consist of quartz-barite-sulfide fissure veins in cataclastic to mylonitic Paleozoic greenstone, carbonate, and trondhjemite; locally, they are in Triassic limestone and rhyolite that generally are in fault contact with the Paleozoic rocks (Karl, 1992, loc. 24). Pyrite and hematite are reported at some of the occurrences; sulfide minerals, inferred from sample analyses, probably are mainly galena and sphalerite.
Variously mineralized samples of greenstone and other country rocks, barite-bearing veins, and quartz-sulfide veins contained up to 2 ppm Ag, 700 ppm Cu, 100 ppm Pb, 700 ppm Zn, more than 5000 ppm Ba, 500 ppm Cr, and 200 ppm Ni; soil and rock samples collected in the 1970s by private interests contained up to 475 ppm Cu and 1100 ppm Zn (Karl, 1992, loc. 24a-f).
Geologic map unit (-131.572679883133, 55.168655749523)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Fissure veins probably are Late Cretaceous or younger.
Alteration of deposit Country rocks locally are sericitized and permeated with hydrothermal hematite.

Production and reserves

Workings or exploration Variously mineralized samples of greenstone and other country rocks, barite-bearing veins, and quartz-sulfide veins contained up to 2 ppm Ag, 700 ppm Cu, 100 ppm Pb, 700 ppm Zn, more than 5000 ppm Ba, 500 ppm Cr, and 200 ppm Ni; soil and rock samples collected in the 1970s by private interests contained up to 475 ppm Cu and 1100 ppm Zn (Karl, 1992, loc. 24a-f).
Indication of production None

References