Unnamed (near Hemlock Bay)

Occurrence in Alaska, United States with commodities Silver, Barium-Barite, Copper, Lead, Zinc

Geologic information

Identification information

Deposit ID 10307686
Record type Site
Current site name Unnamed (near Hemlock Bay)

Geographic coordinates

Geographic coordinates: -131.57276, 55.16874 (WGS84)
Relative position 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.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Barium-Barite Primary
Copper Primary
Lead Primary
Zinc Primary

Materials information

Materials Type of material
Barite Ore
Galena Ore
Pyrite Ore
Sphalerite Ore
Calcite Gangue
Quartz Gangue

Alteration

  • (Local) Country rocks locally are sericitized and permeated with hydrothermal hematite.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Nearby scientific data

(1) -131.57276, 55.16874

Comments on the geologic information

  • 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).
  • Age = Fissure veins probably are Late Cretaceous or younger.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Mining district

District name Ketchikan

Comments on the workings information

  • Workings / 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).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF KC171

Bibliographic references

  • Deposit

    Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360,

  • Deposit

    Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

  • Deposit

    Karl, S.M., 1992, Map and table of mineral deposits on Annette Island, Alaska: U.S. Geological Survey Open-File Report 92-690, 57 p., 1 map, scale 1:63,360.

Comments on the references

  • Primary Reference = Karl, 1992

General comments

Subject category Comment text
Deposit Model Name = Polymetallic veins (Cox and Singer, 1986; model 22c)

Reporter information

Type Date Name Affiliation Comment
Reporter 07-JUL-99 H.C. Berg U.S. Geological Survey