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  3. Mineral Resource Data System (MRDS)

Twentymile River

Occurrence in Alaska, United States with commodity Gold
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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. Nearby scientific data
  9. Economic information about the deposit and operations
  10. Mining district
  11. Links to other databases
  12. Bibliographic references
  13. General comments
  14. Reporter information

Geologic information

Identification information

Deposit ID 10003422
MRDS ID A106179
Record type Site
Current site name Twentymile River

Geographic coordinates

Geographic coordinates: -148.90261, 60.99956 (WGS84)
Relative position Includes upper portions of Twentymile River. Twentymile River also flows in the Anchorage A-6 map and southerly into the Seward Quadrangle. Accurate to within 3 miles. This is locality P-42 of Hoekzema and Fechner (1986).

Site location context

Political divisions (FIPS codes)

Anchorage(Municipality)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Seward D-6(quadrangle 1:63,360 scale)

Seward NW(quadrangle 1:100,000 scale)

Seward C(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Anchorage(hydrologic unit)

Knik Arm(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Chugach National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary

Materials information

Materials Type of material
Gold Ore

Mineral occurrence model information

Model code 119
USGS model code 39a
Deposit model name Placer Au-PGE
Mark3 model number 54

Nearby scientific data

(1) Kaf
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Placer gold is disseminated in poorly- to moderately-washed glacial fluvial gravels along the upper portions of Twentymile Creek. Five alluvium samples from the upper portions of Twentymile River contained from a trace to 0.0073 oz Au/cubic yard (Jansons and others, 1984). Numerous large boulders are present (Hoekzema and Fechner, 1986). The bedrock in the region is Late Cretaceous metasedimentary rocks of the Valdez Group.
  • Age = Quaternary

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Anchorage

Comments on the production information

  • Production Notes = No recorded production, however Hoekzema and Fechner (1986) state the mineral development potential is moderate for small mining operation. Pockets of higher grade material may occur within and adjacent to the river channel (Jansons and others, 1984).

Comments on the workings information

  • Workings / Exploration = Five alluvium samples from the upper portions of Twentymile River contained from a trace to 0.0073 oz Au/cubic yard (Jansons and others, 1984).

Reference information

Bibliographic references

  • Deposit

    Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, Southcentral Alaska: U.S. Bureau of Mines Open-File Report 5-84, 218 p., 2 sheets, scale 1:250,000.

  • Deposit

    Hoekzema, R.B., and Fechner, S.A., 1986, Placer Gold sampling in and near the Chugach National Forest, Alaska: U.S. Bureau of Mines Information Circular 9091, 42 p.

Comments on the references

  • Primary Reference = Jansons and others, 1984

General comments

Subject category Comment text
Deposit Model Name = Placer Au (Cox and Singer, 1986; model 39a)

Reporter information

Type Date Name Affiliation Comment
Reporter 30-JUL-1998 D.P. Bickerstaff U.S. Geological Survey
Reporter 30-JUL-1998 S.W. Huss U.S. Geological Survey

Beyond USGS

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

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.