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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Unnamed (southwest Gravina Island) MRDS details
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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