Unnamed (near Purple Lake)

The Unnamed (near Purple Lake) is a molybdenum and 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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MRDS mine locations are often very general, and in some cases are incorrect. Some mine remains have been covered or removed by modern industrial activity or by development of things like housing. The satellite view offers a quick glimpse as to whether the MRDS location corresponds to visible mine remains.

Site Name

Primary: Unnamed (near Purple Lake)

Commodity

Primary: Molybdenum
Primary: Gold

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: Occurrence
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Not available

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Trondhjemite is sericitized and locally permeated with hydrothermal hematite.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Pyrite
Ore: Magnetite

Comments

Comment (Geology): Geologic Description = The country rock at this site is Silurian trondhjemite (Berg, 1972 [I 684]; Berg and others, 1988). The trondhjemite, which locally is sheared, sericitized, and permeated with hydrothermal hematite, was regionally metamorphosed to greenschist grade in Late Cretaceous time. The occurrences are in sheared, hydrothermally altered trondhjemite, and consist of disseminated pyrite, and of pyrite-magnetite veins associated with a 300-foot-wide shear zone. A sample of rusty, altered, granitic rock contained 0.14 ppm Au; a sample of a pyrite-magnetite vein contained 15 ppm Mo (Karl, 1992, loc. 43a, b).

Comment (Geology): Age = Probably Late Cretaceous or younger.

Comment (Reference): Primary Reference = Karl, 1992

Comment (Workings): Workings / Exploration = A sample of rusty, altered, granitic rock contained 0.14 ppm Au; and a sample of a pyrite-magnetite vein contained 15 ppm Mo (Karl, 1992, loc. 43a, b).

Comment (Deposit): Model Name = Disseminated sulfide and magnetite mineralization of undetermined origin.

References

Reference (Deposit): Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360,

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): Karl, S.M., 1992, Map and table of mineral deposits on Annette Island, Alaska: U.S. Geological Survey Open-File Report 92-690, 57 p., 1 map, scale 1:63,360.

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