Unnamed (southwest of hill 2120)

The Unnamed (southwest of hill 2120) 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 (southwest of hill 2120)

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

Not available

Rocks

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

Analytical Data

Not available

Materials

Ore: Chromite

Comments

Comment (Reserve-Resource): Reserves = This occurrence is estimated to contain between 2,000 and 5,000 tons of chromic oxide. This occurrence and three others nearby (NL003, 004, and 006) contain a combined total of between 17,000 and 37,000 tons of chromic oxide.

Comment (Workings): Workings / Exploration = Chromite occurrences within 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).

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

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

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 NL003, 004, and 006. 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 occurrence is a 3-foot-thick band of nearly massive chromite and thin, parallel bands of chromite (Foley and others, 1984). The chromite occurs as masses of subhedral to anhedral grains that contain evenly distributed intergranular serpentine. Kammerite lines some fractures and slickensides. Traces of uvarovite are also present. Float samples and magnetic anomalies indicate that this occurrence is possibly 300 feet long. It is estimated to contain between 2,000 and 5,000 tons of chromic oxide (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.

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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