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Colby

Prospect in Alaska, United States with commodities Gold, Arsenic
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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. Alteration
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10000900
MRDS ID A011554
Record type Site
Current site name Colby
Related records 10209813

Geographic coordinates

Geographic coordinates: -150.96669, 62.5726 (WGS84)
Relative position C.C. Hawley and Associates, Inc. (1978, Fig. 4.2-B (3)) locate this property in the southeast quarter of Section 28, T. 29 N., R. 9 W., of the Seward Meridian on ridge between Bird and Nugget Creeks.

Site location context

Political divisions (FIPS codes)

Matanuska-Susitna(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Talkeetna C-2(quadrangle 1:63,360 scale)

Talkeetna NE(quadrangle 1:100,000 scale)

Talkeetna(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Yentna River(hydrologic unit)

Susitna River(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Arsenic Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Muscovite Gangue
Sericite Gangue
Zircon Gangue
Pitticite Gangue

Alteration

  • (Local) A thin section of quartz vein shows muscovite, pitticite, zircon and sericite alteration adjacent to and within the dike (Clark and Hawley, 1968).

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock
    Stratigraphic age (youngest) Pliocene
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock

Nearby scientific data

(1) -150.96669, 62.5726
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = At this locality disseminated arsenopyrite occurs in a 4-foot-wide felsite porphyry dike and also in a thin quartz vein, with euhedral quartz and arsenopyrite crystals, that borders the dike (Clark and Hawley, 1968). Alteration adjacent to and within the dike is comprised of muscovite, pitticite, zircon and sericite (Clark and Hawley, 1968). A sample of the felsite porphyry contains 0.80 ppm Au, 5000 ppm As, 1500 ppm Ba, 150 ppm Zr, 50 ppm W (Clark and Hawley, 1968). Regionally Mesozoic marine sedimentary rocks (KJs) are cut by Tertiary (?) felsite dikes (Clark and Hawley, 1968; Reed and Nelson, 1980). Dikes in this prospect area trend N35 to N50E. ? the highest grade lode deposits in Yentna district are in the Colby, Bird (TL040) , and Nugget Creek (TL035) prospects (Hawley and Clark, 1973, p. A6).
  • Age = Tertiary; mineralization is interpreted to be related to the felsite dikes that are described as Tertiary in age by Clark and Hawley (1968).

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Yentna

Comments on the workings information

  • Workings / Exploration = Four or five shallow prospect pits were dug on the property by independant prospectors. In addition reconnaissance mapping, stream silt and rock sampling have been done by the U.S. Geological Survey (Clark and Hawley, 1968; Reed and Nelson, 1980).

Reference information

Bibliographic references

  • Deposit

    Clark, A.L., and Hawley, C.C., 1968, Reconnaissance geology, mineral occurrences, and geochemical anomalies of the Yentna district, Alaska: U.S. Geological Survey Open-File Report 68-35, 64 p.

  • Deposit

    Hawley, C.C., and Clark, A.L., 1973, Geology and mineral deposits of the upper Chulitna district, Alaska: U.S. Geological Survey Professional Paper 758-A, p. 1-10, 2 sheets, scale 1:250,000 and 1:500,000.

  • Deposit

    MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000.

  • Deposit

    C.C. Hawley and Associates, Inc., 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska: U.S. Bureau of Mines Open-File Report 24-78, 275 p., 7 plates.

  • Deposit

    Reed, B.L., Nelson, S.W., Curtin, G.C., and Singer, D.A., 1978, Mineral resources map of the Talkeetna Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-D, 1 sheet, scale 1:250,000.

  • Deposit

    Cobb, E.H., and Reed, B.L., 1980, Summaries of data and lists of reference to metallic and selected nonmetallic mineral deposits in the Talkeetna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-884, 106 p.

  • Deposit

    Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, scale 1:250,000.

  • Deposit

    Clark, A.L., and Cobb, E.H., 1972, Metallic mineral resources map of the Talkeetna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-369, 1 sheet, scale 1:250,000.

Comments on the references

  • Primary Reference = Clark and Hawley, 1968

General comments

Subject category Comment text
Deposit Model Name = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a).
Deposit Other Comments = the highest grade lode deposits in Yentna district are Colby, Bird (TL040), and Nugget Creek (TL035) prospects (Hawley and Clark, 1973, p. A6).

Reporter information

Type Date Name Affiliation Comment
Reporter 10-AUG-1998 Madelyn A. Millholland Millholland & Associates

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.