Unnamed (northwest of hill 1325)

The Unnamed (northwest of hill 1325) is a chromium 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 (northwest of hill 1325)

Commodity

Primary: Chromium

Location

State: Alaska
District: Kaiyuh

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: Podiform chromite (minor)

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Magmatic Segregation

Rocks

Role: Host
Age Type: Host Rock
Age Young: Jurassic

Analytical Data

Not available

Materials

Ore: Chromite

Comments

Comment (Workings): Workings / Exploration = Chromite occurrences in the Kaiyuh Hills were first documented in 1980 by C.C. Hawley and Associates, Inc., during their investigations for Armco Mineral Exploration, Ltd. The Bureau of Mines examined four of the occurrences in 1982 and published a report in 1984 (Foley and others, 1984).

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Jurassic, the age of the ultramafic hostrocks (Patton and others, 1977).

Comment (Geology): Age = Host rock is Jurassic.

Comment (Reference): Primary Reference = Foley and others, 1984

Comment (Reserve-Resource): Reserves = This occurrence is estimated to contain between 1,000 and 4,000 tons of chromic oxide. It and three others nearby (NL004-006) contain a combined resource of 17,000 to 37,000 tons of chromic oxide.

Comment (Deposit): Model Name = Podiform chromite (Cox and Singer, 1986; model 8a)

Comment (Deposit): Other Comments = There are a total of 21 chromite occurrences known along a 6-mile-long, northeast-trending exposure of ultramafic rocks in the Kaiyuh Hills. This occurrence is one of the four largest such occurrences. The other three are described in NL004-006. Foley and others (1984) list the locations of the other 17 occurrences.

Comment (Geology): Geologic Description = Chromite occurrences in the Kaiyuh Hills were first documented in 1980 by C.C. Hawley and Associates, Inc., during their investigations for Armco Mineral Exploration, Ltd. The U.S. Bureau of Mines examined four of the occurrences in 1982, and published a report in 1984 (Foley and others, 1984). Twenty-one occurrences were located within a northeast-trending, approximately 6-mile-long body of dunite and pyroxene peridotite in the Kaiyuh Hills. The largest 4 occurrences are described in this record and in records NL004, NL005, and NL006. These four occurrences are estimated to contain a combined total of between 17,000 and 37,000 tons of chromic oxide (Foley and others, 1984).? the Kaiyuh Hills are underlain by a portion of the Rampart ophiolite belt that is offset along the Kaltag fault from the remainder of the belt. The belt comprises two tectonic units: an upper unit of ultramafic and gabbroic rocks and a lower unit of mafic volcanic rocks, diabase, and chert (Patton and others, 1977). Ultramafic rocks of the upper unit, which contain the chromite occurrences, are exposed along a 24-mile-long, northeast-striking belt in the Kaiyuh Hills (Foley and others, 1984). At the southwestern end of the belt is a 6-square-mile area underlain mostly by a body of dunite. This dunite contains more than 90% olivine, sparsely disseminated chromite, and locally banded segregations of disseminated to massive chromite. Nodular chromite was observed at one location. At the northeastern end of this body, the dunite grades into pyroxene peridotite interlayered with dunite. This part of the body also contains chromite bands ranging in thickness from less than 1 inch to 3 feet. The dunite layers range from a few inches to several hundred feet thick. The pyroxene peridotite is mostly harzburgite. Minor amounts of wehrlite and lherzoliteare also present (Foley and others, 1984).? This site is labeled occurrence 1 by the U.S. Bureau of Mines (Foley and others, 1984). The describe it as a 5-by-750-foot area of float containing 3%- 5% banded and massive chromite, and estimate that it contains between 1,000 and 4,000 tons of chromic oxide. Three samples of float contained 10%-13.3% chromite.

References

Reference (Deposit): Patton, W.W. Jr., Tailleur, I.L., Brosge, W.P., and Lanphere, M.A., 1977, Preliminary report on the ophiolites of northern and western Alaska: Oregon Department of Geologic and Mineral Industry Bulletin 95, p. 51-57.

Reference (Deposit): Foley, J.Y., Hinderman, T., Hawley, C.C., Kirby, D.E., and Mardock, C.L., 1984, Chromite occurrences in the Kaiyuh Hills, west-central Alaska: U.S. Bureau of Mines Open-File Report 178-84, 20 p.

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