Unnamed (southwest Gravina Island)

The Unnamed (southwest Gravina Island) is a gold and silver mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Unnamed (southwest Gravina Island)

Commodity

Primary: Gold
Primary: Silver
Secondary: Barium-Barite

Location

State: Alaska
District: Ketchikan

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Polymetallic veins

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Local iron-staining.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Sphalerite
Ore: Galena
Ore: Chalcopyrite
Ore: Barite
Gangue: Quartz

Comments

Comment (Commodity): Gangue = Carbonate

Comment (Deposit): Model Name = Polymetallic veins? (Singer and Cox, 1986; model 22c)

Comment (Geology): Age = The mineralized fault breccia is Late Triassic or younger.

Comment (Reference): Primary Reference = Berg, 1973; Koch and Elliott, 1978 (OFR 78-156A)

Comment (Workings): Workings / Exploration = In 1969, workings that probably date to the early 1900s consisted of an approximately 21-foot-long adit. Analyses of samples of the breccia and the adjacent country rocks showed up to 70 ppm Ag, 0.15 ppm Au, more than 0.5% Ba, 700 ppm Cu, 1.5% Pb, and more than 1% Zn (Koch and Elliott, 1978 [OFR 78-156A]).

Comment (Geology): Geologic Description = The country rocks in the general area of this prospect are complexly folded and faulted Upper Triassic carbonate, clastic, and basaltic volcanic strata (Berg, 1973; Berg and others, 1980). The deposit consists of a 3-foot-wide fault breccia in a mafic dike(?) that is structurally mixed with the Upper Triassic sedimentary and volcanic rocks. The breccia weathers orange or red, and contains quartz, carbonate, barite, and small amounts of unidentified sulfide minerals, which also are sparsely disseminated in the adjacent country rocks. Analyses of samples of the breccia and the adjacent country rocks showed up to 70 ppm Ag, 0.15 ppm Au, more than 0.5% Ba, 700 ppm Cu, 1.5% Pb, and more than 1% Zn (Koch and Elliott, 1978 [OFR 78-156A]). The analytical data indicate that the unidentified sulfide minerals probably include sphalerite, chalcopyrite, and argentiferous galena. In 1969, workings that probably date to the early 1900s consisted of an approximately 21-foot-long adit.

References

Reference (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.

Reference (Deposit): Koch, R.D., and Elliott, R.L., 1978, Analyses of rock samples from Ketchikan quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 78-156-A, 162 p., 1 sheet, scale l:250,000.

Reference (Deposit): Berg, H.C., 1973, Geology of Gravina Island Alaska: U.S. Geological Survey Bulletin 1373, 41 p.

Reference (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.

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