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Fishhook

Prospect in Alaska, United States with commodities Silver, Gold, Barium-Barite, Copper, Molybdenum, Lead, Antimony
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Geologic information

Identification information

Deposit ID 10001749
MRDS ID A012533
Record type Site
Current site name Fishhook

Geographic coordinates

Geographic coordinates: -141.31264, 63.79976 (WGS84)
Relative position The Fishhook prospect covers an area of approximately 2 square miles. It is location 7 of Eberlein and others (1977). It is located to the west of the Fishhook Bend of the Sixtymile River. Accessibility is limited; the Taylor highway passes about 24 miles west of the prospect. However, rough overland access is available from Canada (Curt Freeman, unpublished data, 1998). The coordinates are for the approximate center of the claim block, but the center of mineralization and prospecting could be elsewhere within the claim block. The location is accurate to within 1 mile.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Barium-Barite Secondary
Copper Secondary
Molybdenum Secondary
Lead Secondary
Antimony Secondary

Comments on the commodity information

  • Ore Material = sulfosalts
  • Ore Material = sulfosalts

Materials information

Materials Type of material
Chalcopyrite Ore
Galena Ore
Gold Ore
Molybdenite Ore
Pyrite Ore
Silver Ore
Stibnite Ore
Hematite Gangue
Quartz Gangue

Alteration

  • (Local) Intense hydrothermal alteration and silicification is found in many of the NE-trending fault zones and in portions of intrusive units at the prospect (Curt Freeman, unpublished data, 1998).

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Gneiss

Nearby scientific data

(1) -141.31264, 63.79976
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Comments on the geologic information

  • Geologic Description = The country rock within the Fishhook prospect area is augen gneiss having a possible igneous protolith (Mertie, 1931; Foster, 1970). This protolith has a possible emplacement age (inferred from dating other exposures in the region) of Devonian to Mississippian (360 Ma), with resets in the Late Jurassic (190 Ma) and Early to mid-Cretaceous (135-107 Ma) time (Dusel-Bacon and Aleinikoff, 1985). Cretaceous-Tertiary, fine-grained biotite granite, granodiorite, monzodiorite, and a coarse-grained alkali granite intrude the augen gneiss and are exposed in small outcrops at the prospect. Tertiary (?) volcanics are also present (Gill, 1977). ? Local structures are dominated by numerous, high-angle, NE-trending fault zones. Many subordinate fault zones in the area parallel the NE strike and possibly reflect underlying igneous activity (Curt Freeman, unpublished data, 1998). The mineralization at the Fishhook prospect appears to be structurally controlled by the NE-trending faults. Minerals include chalcopyrite, galena, gold, molybdenite, pyrite, silver, sulfosalts, and stibnite. The more highly mineralized areas occur as breccias along the NE faults. The plutonic rocks also contain elevated values of lead, silver, barium, antimony, and gold. Anomalous bismuth along some of the faults suggests a plutonic-source fluid. Extensive hydrothermal alteration and silicification is present in many of the fault zones (Curt Freeman, unpublished data, 1998).? This property was examined in the 1970's as a porphyry-copper deposit, but no significant grades of copper were found. Soil sampling, rock-chip sampling, and stream-sediment sampling were done on the property in the 1970's. In 1978, a shallow drill hole was put in, but no significant mineralization was found. In recent years, soil and rock chip sampling, geologic mapping, and a ground-based magnetometer survey have been conducted (Curt Freeman, unpublished data, 1998).
  • Age = Late Cretaceous-early Tertiary.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Active

Mining district

District name Fortymile

Comments on the workings information

  • Workings / Exploration = Soil sampling, rock chip sampling, and stream sediment sampling were carried out in the 1970's. In 1978, one shallow drill hole was put in, but did not encounter significant mineralization. In recent years, soil and rock-chip sampling, geologic mapping, and a ground-based magnetometer survey have been conducted (Curt Freeman, unpublished data, 1998). This prospect was examined in the 1970's as a porphyry-Cu deposit, but no significant grades of copper were found (J.M. Messing, oral communication, 1998).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012533
USGS Alaska Resource Data File ARDF TC009

Bibliographic references

  • Deposit

    Mertie, J.B., Jr., 1931, A geologic reconnaissance of the Dennison Fork District, Alaska: U.S. Geological Survey Bulletin 827, 44 p.

  • Deposit

    Foster, H.L., 1970, Reconnaissance geologic map of the Tanacross quadrangle, Alaska: U.S. Geological Survey Miscellaneous Geological Investigations Map I-593, 1 sheet, scale 1:250,000.

  • Deposit

    Eberlein, G.D., Chapman, R.M., Foster, H.L., and Gassaway, J.S., 1977, Map and table describing known metalliferous and selected nonmetalliferous mineral deposits in central Alaska: U.S. Geological Survey Open-File Report 77-168-D, 132 p., 1 map, scale 1:1,000,000.

  • Deposit

    Gill, R., 1977, Geology and mineral deposits of the southwest quarter of the Tanacross D-1 quadrangle, Alaska: Golden, Colorado School of Mines, M.Sc. thesis, 129 p.

  • Deposit

    Cobb, E.H., and Eberlein, G.D., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Big Delta and Tanacross quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1086, 77 p.

  • Deposit

    Dusel-Bacon, C., and Aleinikoff, J.N., 1985, Petrology and tectonic significance of augen gneiss from a belt of Mississippian granitoids in the Yukon-Tanana terrane, east-central Alaska: Geological Society of America Bulletin, v. 96, p. 411-425.

Comments on the references

  • Primary Reference = This description

General comments

Subject category Comment text
Deposit Model Name = Plutonic-related (?) ore deposit along NE-trending faults

Reporter information

Type Date Name Affiliation Comment
Reporter 13-APR-99 Cameron, C.E. Alaska Division of Geological and Geophysical Surveys