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Japan Bay

Prospect in Alaska, United States with commodities Silver, Barium-Barite, Lead, Zinc
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Geologic information

Identification information

Deposit ID 10001614
MRDS ID A012378
Record type Site
Current site name Japan Bay

Geographic coordinates

Geographic coordinates: -131.57676, 55.1778 (WGS84)
Relative position This site, informally called the Japan Bay prospect, is on the southwest shore of inner Sylburn Harbor, about 0.5 mile from its head. The site is in section 20, T. 77 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 18 in Berg (1972 [I 684]), loc. 136 in Elliott and others (1978), and loc. 19 in Karl (1992). The location is accurate within a few hundred feet.
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Geographic areas

Country State
United States Alaska

Commodities

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

Materials information

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

Alteration

  • (Local) Probable local permeation of some of the country rocks by hydrothermal hematite.

Mineral occurrence model information

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

Host and associated rocks

  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite
    Stratigraphic age (youngest) Late Permian
  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite

Nearby scientific data

(1) -131.57676, 55.1778
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Comments on the geologic information

  • Geologic Description = The country rocks in the area of this site are recrystallized, locally intensely sheared and hematite?-altered, Upper Triassic rhyolite and limestone (Berg, 1972). The rocks are complexly folded and faulted, and were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.? the deposit consists chiefly of barite veins in a 10-foot-wide shear zone in brecciated rhyolite (Karl, 1992, loc. 19). The veins contain minor quartz and calcite, and clots, laminae, and stringers of hematite, galena, and sphalerite. Barite forms irregular veins and masses up to 3 feet wide. The sheared rhyolite contains disseminated sulfides.? the prospect was explored in the 1970s and 1980s by private interests (Hawley and Associates, in Karl, 1992). The work included 5 diamond drill holes, soil surveys, and other studies. The drill holes indicated that the barite zone dips 25 W, and barite was intercepted as deep as 150 feet. The soil surveys indicated that the barite zone is about 100 feet wide and extends about 1000 feet to the south. The barite lenses and veins are sparse and irregular, and barite grade is low, but the deposit size is estimated to exceed 1,000,000 tons. Karl's (1992, loc. 19a, b) samples of the barite and of variously mineralized country rocks contained as much as 0.11 ppm Au, 50 ppm Ag, 1% Pb, 700 ppm Zn, and 10 ppm Mo.
  • Age = Late Triassic or younger.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Both metallic and non-metallic

Mining district

District name Ketchikan

Comments on the reserve resource information

  • Reserves = the deposit size is estimated to exceed 1,000,000 tons (Karl, 1992, loc. 19).

Comments on the workings information

  • Workings / Exploration = The prospect was explored in the 1970s and 1980s by private interests (Hawley and Associates, in Karl, 1992, loc. 19). The work included 5 diamond drill holes, soil surveys, and other studies. The drill holes indicated that the barite zone dips 25 west, and barite was intercepted as deep as 150 feet. The soil surveys indicated that the barite zone is about 100 feet wide and extends about 1000 feet to the south. The barite lenses and veins are sparse and irregular, and barite grade is low, but the deposit size is estimated to exceed 1,000,000 tons. Karl's (1992, loc. 19a, b) samples of the barite and of variously mineralized country rocks contained as much as 0.11 ppm Au, 50 ppm Ag, 1% Pb, 700 ppm Zn, and 10 ppm Mo.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012378
USGS Alaska Resource Data File ARDF KC139

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

    Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 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 06-JUL-1999 H.C. Berg U.S. Geological Survey