Unnamed (east of Brady Glacier)

The Unnamed (east of Brady Glacier) is a iron 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: Unnamed (east of Brady Glacier)

Commodity

Primary: Iron
Secondary: Silver
Secondary: Molybdenum
Secondary: Copper

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

Physiography

Not available

Mineral Deposit Model

Model Name: Skarn Fe

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Skarn, contact metasomatic deposit.

Rocks

Name: Diorite
Role: Associated
Age Type: Host Rock
Age Young: Late Permian

Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Pliocene

Analytical Data

Not available

Materials

Ore: Chalcopyrite
Ore: Magnetite
Ore: Molybdenite
Ore: Pyrite
Gangue: Garnet
Gangue: Quartz

Comments

Comment (Reference): Primary Reference = Kimball and others, 1978

Comment (Geology): Age = Tertiary.

Comment (Exploration): Status = Inactive

Comment (Geology): Geologic Description = The country rocks in the area of this occurrence consist of a northwest-trending belt of Paleozoic marble bounded on the west by foliated granodiorite of Cretaceous age and on the east by leucocratic biotite granite and affiliated rocks of Tertiary age (Brew and others, 1978). Magnetite lenses as much as 15 feet thick and 35 feet long occur in northwest-striking, steeply dipping bodies in limy hostrocks intermixed with leucocratic granitic rock. The limy rocks are partly converted to skarn. MacKevett and others (1971, p. 72, table 9) reported more than 10 percent iron, 1000 ppm copper, and 7 to 15 ppm molybdenum in grab and selected samples collected at the site. They also reported magnetic anomalies of as much as 5000 gammas, but believed that the iron-rich lenses were too small to be commercially significant.? A selected sample collected by the U.S. Bureau of Mines (Kimball and others, 1978, p. C267) contained 1400 ppm copper, 1.5 ppm silver, and greater than 20 percent iron. Samples of lenses that ranged from 4.5 to 35 feet across contained more than 30 percent iron and as much as 750 ppm copper.

Comment (Workings): Workings / Exploration = There are no workings. The Geological Survey and Bureau of Mines sampled only surface exposed occurrences. Samples collected by MacKevett and others (1971) contained 7-15 ppm molybdenum, 1000 ppm copper and greater than 10 percent iron. Kimball and others (1978) reported iron to greater than 30 percent and, in one selected sample, 1400 ppm copper.? the magnetite-rich skarn lenses are as much as 35 feet long and are traceable through a vertical range of at least 400 feet.

Comment (Deposit): Model Name = Fe skarn (Cox and Singer, 1986; model 18d).

Comment (Deposit): Other Comments = Although some of the skarn bodies are rich enough to constitute iron ore, they are too small to be exploited. The proximity of this site to the Threesome Mountain (MF070) molybdenum-tungsten area, also affiliated with a Tertiary granite, suggests that the area could contain skarns having more molybdenum and copper.? the site is in Glacier Bay National Park and Preserve.

References

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): 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): 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): 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.

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