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Unnamed (near Sylburn Harbor)

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

Identification information

Deposit ID 10307697
Record type Site
Current site name Unnamed (near Sylburn Harbor)

Geographic coordinates

Geographic coordinates: -131.58676, 55.17774 (WGS84)
Relative position This site represents 6 occurrences along about a mile of the south shore of Sylburn Harbor, about 0.7-1.0 miles east of Driest Point. The occurrences are in section 20, T. 77 S., R. 92 E., of the Copper River Meridian. The map site is at the approximate midpoint of this group of occurrences. The site corresponds to loc. 17 in Berg (1972 [I 684]), and loc. 21a-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
Lead Primary
Zinc Primary

Materials information

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

Alteration

  • (Local) The rocks locally are sericitized, silicified, dolomitized, 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) -131.58676, 55.17774
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Comments on the geologic information

  • Geologic Description = The country rocks in the area of this site are 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; Berg and others, 1988; Karl, 1992). The rocks are folded and locally intensely sheared, sericitized, silicified, dolomitized, and permeated with hydrothermal hematite. The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrences consist of up to 3-foot-thick pods of barite in dolomite, and of barite-calcite fissure veins in sheared and brecciated rhyolite (Berg, 1972, loc. 17; Karl, 1992, loc. 21a-f). The dolomite and rhyolite contain galena and sphalerite; the barite contains argentiferous galena and sphalerite. The barite in the pods occurs as radial blades, with rosettes of barite up to 20 inches in diameter. . Samples of brecciated dolomite, massive dolomite, and sheared metabasite with calcite veins contained up to 100 ppm Pb, 300 ppm Zn, and 500 ppm Ba; a sample of barite contained 7 ppm Ag and 7000 ppm Zn; a sample of silicified tuff contained 1.5 ppm Ag, 1000 ppm Pb, 1500 ppm Zn, and 150 ppm Cr; samples of volcanic agglomerate with calcite veins, and of mylonitic calcareous conglomerate, contained up to 200 ppm Pb and 700 ppm Zn; and samples of pyritic rhyolite tuff-breccia and pyritic gray limestone contained up to 150 ppm Pb and 300 ppm Zn (Karl, 1992, loc. 21a-f). A mapping and soil survey by private interests in the 1970s indicated that the barite-rich zone extends for about 210 feet along the west shore of a small peninsula, and for about 400 feet inland from there (Karl, 1992).
  • Age = the 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 = Samples of brecciated dolomite, massive dolomite, and sheared metabasite with calcite veins contained up to 100 ppm Pb, 300 ppm Zn, and 500 ppm Ba; a sample of barite contained 7 ppm Ag and 7000 ppm Zn; a sample of silicified tuff contained 1.5 ppm Ag, 1000 ppm Pb, 1500 ppm Zn, and 150 ppm Cr; samples of volcanic agglomerate with calcite veins, and of mylonitic calcareous conglomerate, contained up to 200 ppm Pb and 700 ppm Zn; and samples of pyritic rhyolite tuff-breccia and pyritic gray limestone contained up to 150 ppm Pb and 300 ppm Zn (Karl, 1992, loc. 21a-f). A mapping and soil survey by private interests in the 1970s indicated that the barite-rich zone extends for about 210 feet along the west shore of a small peninsula, and for about 400 feet inland from there (Karl, 1992).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF KC182

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