The Sentinel is a gold 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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Sentinel MRDS details
Site Name
Primary: Sentinel
Commodity
Primary: Gold
Secondary: Lead
Secondary: Silver
Location
State: Alaska
District: Juneau
Land Status
Not available
Holdings
Not available
Workings
Not available
Ownership
Not available
Production
Not available
Deposit
Record Type: Site
Operation Category: Past Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:
Physiography
Not available
Mineral Deposit Model
Model Name: Low-sulfide Au-quartz vein
Orebody
Not available
Structure
Not available
Alterations
Alteration Type: L
Alteration Text: Intensely altered haloes in granodiorite around veins.
Rocks
Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Late Cretaceous
Analytical Data
Not available
Materials
Ore: Galena
Ore: Hematite
Ore: Plumbojarosite
Ore: Gold
Gangue: Quartz
Comments
Comment (Geology): Age = Late Cretaceous or younger.
Comment (Reference): Primary Reference = Rossman, 1959 (B 1058-B)
Comment (Reserve-Resource): Reserves = None: Some potential especially if nearby vein swarm is auriferous.
Comment (Commodity): Ore Material = Gold (native)
Comment (Production): Production Notes = Joe Ibach is reported to have transported high-grade oxidized gold-bearing ore to Lemesurier Island where it was milled.
Comment (Workings): Workings / Exploration = The Sentinel vein was discovered and mined in shallow open cuts by Joe Ibach shortly after Glacier Bay National Monument was opened to mining in 1936. Shallow surface cuts are now obscured by overburden and vegetation.
Comment (Exploration): Status = Inactive
Comment (Geology): Geologic Description = The Sentinel vein is hosted by granodiorite of Cretaceous age; it is locally covered by surface alluvium (Rossman, 1959, B 1058-B. pl. 4). The vein is similar in strike and characteristics to the Rainbow (MF027). The vein is steep and strikes northeast. The vein, six to 10 inches wide, is within an altered envelope about 1-foot thick. Rossman (1959, p. 54) noted that vein was quartz poor, and consisted mainly of altered granodiorite containing disseminated galena, other sulfides, and occasionally gold. The vein was discovered by Joe Ibach; it had a cavity a few feet long at the discovery cut. The floor of the cavity contained a red oxide rich in gold. The oxide has been inferred to be lead oxide (plumbojarosite?), but it probably included iron oxides, possibly hematite. The high-grade ore was mined by Ibach. ? the Sentinel is at the head of a swarm of veins, also of northeast to east- northeast strike, which extend over about 1600 feet of beach front below the mine. Apparently most of the veins have not been sampled.? MacKevett and others, (1971, p. 60, also table 11, loc. D) found about 0.1 oz/ton gold in a nearby vein parallel to the Sentinel.
Comment (Deposit): Other Comments = Ore was from a nearly quartz-free shear zone in granodiorite. Rossman (1959, p. 54) reports galena and other sulfides disseminated along vein-bearing fault. The Sentinel and Rainbow (MF027) were discovered in 1936 after the National Monument was reopened for mining. The vein is now in Glacier Bay National Park and Preserve.
Comment (Commodity): Gangue = alteration minerals of granodiorite
Comment (Deposit): Model Name = Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
References
Reference (Deposit): Rossman, Darwin, 1959, Geology and ore deposits in the Reid Inlet area, Glacier Bay, Alaska: U.S. Geological Survey Bulletin 1058-B, p. 33-58.
Reference (Deposit): MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.
Reference (Deposit): Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375.
Reference (Deposit): Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p.
Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Mount Fairweather quadrangle, AK: U.S. Geological Survey Miscellaneous Field Study Map MF-436, 1 sheet, scale 1:250,000.
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