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Unnamed (east of hill 2120)

Occurrence in Alaska, United States with commodity Chromium
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Mineral occurrence model information
  8. Host and associated rocks
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10002523
MRDS ID A013466
Record type Site
Current site name Unnamed (east of hill 2120)

Geographic coordinates

Geographic coordinates: -156.59809, 64.21947 (WGS84)
Relative position This occurrence is in the southern Kaiyuh Hills, 36 miles south of Galena. It is in a body of dunite exposed in a 6-square-mile area between the Yuki River and the East Fork Yuki River. The occurrence is at an elevation of approximately 1500 feet, about 1.7 miles east of hill 2120. It corresponds to occurrence 21 of Foley and others (1984). The location is accurate within 500 feet.

Site location context

Political divisions (FIPS codes)

Yukon-Koyukuk(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Nulato A-2(quadrangle 1:63,360 scale)

Nulato SE(quadrangle 1:100,000 scale)

Nulato(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Chromium Critical Primary

Materials information

Materials Type of material
Chromite Ore

Mineral occurrence model information

Model code 15
USGS model code 8a
Deposit model name Podiform chromite (minor)
Mark3 model number none

Host and associated rocks

  • Host or associated Host
    Rock type
    Stratigraphic age (youngest) Jurassic

Nearby scientific data

(1) -156.59809, 64.21947
ListMap

Economic information

Comments on the geologic information

  • 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 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 005. 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 consists of a 75- by 300-foot zone of discontinuous bands of chromite up to 2.5 inches thick and 1.5 feet long. The chromite occurs as highly fractured, subhedral to anhedral crystals disseminated in serpentinized dunite. Fractures in the chromite are filled with pale green serpentine. Chalky white to pale blue magnesite coats weathered surfaces (Foley and others, 1984). This zone contains approximately 3% chromite, and is estimated to contain between 3,000 and 6,000 tons of chromic oxide (Foley and others, 1984).
  • Age = Jurassic, the age of the ultramafic hostrocks (Patton and others, 1977).
  • Age = Host rock is Jurassic.

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Kaiyuh

Comments on the reserve resource information

  • Reserves = This occurrence is estimated to contain between 3,000 and 6,000 tons of chromic oxide. This occurrence and three others nearby (NL003, 004, and 005) contain a combined total of between 17,000 and 37,000 tons of chromic oxide.

Comments on the workings information

  • 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).

Reference information

Bibliographic references

  • 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.

  • 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.

Comments on the references

  • Primary Reference = Foley and others, 1984

General comments

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

Reporter information

Type Date Name Affiliation Comment
Reporter 07-AUG-01 Cameron, C.E. Northern Associates Inc.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Alaska resources

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