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Sentinel

Past Producer in Alaska, United States with commodities Gold, Silver, Lead
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10097534
MRDS ID A013154
Record type Site
Current site name Sentinel
Related records 10258107

Geographic coordinates

Geographic coordinates: -136.83601, 58.87139 (WGS84)
Relative position The Sentinel mine is at an elevation of about 900 feet 0.4 mile south of the Rainbow (MF027) adit on the northeast-sloping sidehill above the mouth of Reid Inlet. The location is accurate within 100 feet. The Sentinel is location 21 of Cobb (1972).

Site location context

Political divisions (FIPS codes)

Hoonah-Angoon(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Mount Fairweather D-3(quadrangle 1:63,360 scale)

Mount Fairweather NE(quadrangle 1:100,000 scale)

Mount Fairweather(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Glacier Bay(hydrologic unit)

Northern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Glacier Bay National Park(National Park)

National Park NPS(Type of land area)

NPS(Federal land areas administered by NPS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Silver Secondary
Lead Secondary

Comments on the commodity information

  • Gangue = alteration minerals of granodiorite
  • Ore Material = Gold (native)

Materials information

Materials Type of material
Galena Ore
Hematite Ore
Plumbojarosite Ore
Gold Ore
Quartz Gangue

Alteration

  • (Local) Intensely altered haloes in granodiorite around veins.

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite
    Stratigraphic age (youngest) Late Cretaceous
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite

Nearby scientific data

(1) -136.83601, 58.87139
ListMap

Economic information

Comments on the geologic information

  • 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.
  • Age = Late Cretaceous or younger.

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Juneau

Comments on the production information

  • Production Notes = Joe Ibach is reported to have transported high-grade oxidized gold-bearing ore to Lemesurier Island where it was milled.

Comments on the reserve resource information

  • Reserves = None: Some potential especially if nearby vein swarm is auriferous.

Comments on the workings information

  • 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.

Reference information

Bibliographic references

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

Comments on the references

  • Primary Reference = Rossman, 1959 (B 1058-B)

General comments

Subject category Comment text
Deposit Model Name = Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
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.

Reporter information

Type Date Name Affiliation Comment
Reporter 08-APR-99 Hawley, C.C. Hawley Resource Group

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

External references

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.