Incas

The Incas 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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Site Name

Primary: Incas

Commodity

Primary: Gold
Secondary: Arsenic

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: Rossman (1959) notes alteration (bleaching?) along the 2000-foot strike exposure of the vein fissure.

Rocks

Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Late Cretaceous

Analytical Data

Not available

Materials

Ore: Pyrite
Ore: Arsenopyrite
Ore: Gold
Gangue: Calcite
Gangue: Quartz

Comments

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Tertiary.

Comment (Reference): Primary Reference = Rossman, 1959 (B 1058-B)

Comment (Deposit): Other Comments = Small pods of gold-bearing quartz exist along an altered but weakly mineralized shear zone. Best chances for ore are believed to be in the surface pods of quartz or in secondary fissures opened near the strong north-trending vein fissure. The vein is not well explored at depth. The Incas vein is in Glacier Bay National Park and Preserve.

Comment (Geology): Geologic Description = The Reid Inlet gold area is mainly underlain by granitic rocks of Cretaceous age (Brew and others, 1978). The area was mapped in detail by Rossman (1959, B 1058-B). ? the Incas is a productive north-striking, steeply-dipping vein fissure 1-3-feet thick with lenses of quartz and calcite in a shear zone. Rossman (1959) traced the vein for about 2000 feet and found free gold in all quartz lenses. Locally, gold may have been concentrated by supergene enrichment. Workings driven below the surface outcrops found only low grade quartz veins. The Incas structure is subparallel to and similar geologically to the Monarch vein fissure (MF026). Rossman (1959, plate 4) mapped another subparallel vein about 400-feet east of the Incas vein; the vein was partly covered by colluvium.

Comment (Workings): Workings / Exploration = Incas was discovered in 1924 by Joe Ibach and is one of the earliest discoveries in the district. Claims were located by Ibach and famous Alaska novelist, Rex Beach, in 1936 after Glacier Bay National Monument was opened for mining (Kimball and others, 1978, p. C217). Gold, possibly enriched by supergene processes, was mined along the exposed vein fissure for about 60 feet near an elevation of 1100 feet. A crosscut tunnel was driven below the stoped area for about 170 feet. Near the face of the crosscut, the adit drifts for about 40 feet along a fissure reasonably inferred to be on the same vein mined at the surface. MacKevett found only about 0.029 oz/ton gold in narrow samples taken from the underground workings. One sample contains 20,000 ppm arsenic (MacKevett and others, table 11, location G).

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

Comment (Commodity): Ore Material = Gold (native)

References

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.

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): 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.

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