Gnat

Prospect in Alaska, United States with commodities Copper, Molybdenum, Lead, Gold

Geologic information

Identification information

Deposit ID 10001551
MRDS ID A012298
Record type Site
Current site name Gnat

Geographic coordinates

Geographic coordinates: -130.91066, 55.83087 (WGS84)
Relative position The Gnat prospect is at an elevation of about 150 feet in a narrow gorge in the north wall of Chickamin River canyon, about 1250 feet N22W of Wolf cabin at the mouth of the Chickamin River. The site is in section 6, T. 70 S., R. 95 E., of the Copper River Meridian. It corresponds to loc. P-20 in Berg and others (1977, p. 121), and loc. 21 in Elliott and others (1978). The location is accurate within about 300 feet.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Molybdenum Primary
Lead Primary
Gold Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Galena Ore
Molybdenite Ore
Pyrite Ore
Albite Gangue
Quartz Gangue

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Host and associated rocks

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

Nearby scientific data

(1) -130.91066, 55.83087

Comments on the geologic information

  • Geologic Description = The country rocks in the area of the Gnat prospect is Tertiary or Cretaceous gneissic quartz diorite of the Coast Range batholith that locally contains inclusions of metasedimentary rocks (Berg and others, 1988). The quartz diorite near the prospect is cut by at least one two-foot-thick dike of altered felsic rock (Berg and others, 1977, p. 121).? the Gnat prospect consists of a glassy quartz-albite fissure vein 5.5 feet to 9.5 feet thick that strikes N20W and dips 59-80NE (Berg and Cobb, 1967, p. 182-183; Berg and others, 1977, p. 121). The vein is in gneissic quartz diorite and contains chalcopyrite, molybdenite, galena, and pyrite. The sulfides are relatively abundant for about 1.5 feet below the hanging wall; the rest of the vein is low in visible sulfides. Several channel and composite samples of the vein and of float probably derived from the vein assayed up to 1400 ppm Cu, 1500 ppm Pb, and 4700 ppm Mo (Berg and others, 1977, table 12). The Gnat deposit was staked about 1900, when the vein probably was prospected chiefly for gold (Buddington, 1929, p. 120 [B 807]; Berg and Cobb, 1967, p. 182-183). There is no record of any workings, or of any recovery of gold from the vein, but there probably was some small early production.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Ketchikan

Comments on the production information

  • Production Notes = There is no record of any workings, or of any recovery of gold from the vein, but there probably was some small early production.

Comments on the workings information

  • Workings / Exploration = The Gnat deposit was staked about 1900, when the vein probably was prospected chiefly for gold (Buddington, 1929, p. 120; Berg and Cobb, 1967, p. 182-183). Several channel and composite samples of the vein and of float probably derived from the vein assayed up to 1400 ppm Cu, 1500 ppm Pb, and 4700 ppm Mo (Berg and others, 1977, table 12).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012298
USGS Alaska Resource Data File ARDF KC021

Bibliographic references

  • Deposit

    Buddington, A.F., 1929, Geology of Hyder and vicinity, southeastern Alaska, with a reconnaissance of Chickamin River: U.S. Geological Survey Bulletin 807, 124 p.

  • Deposit

    Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

  • Deposit

    Berg, H.C., Elliott, R.L., Smith, J.G., Pittman, T.L., and Kimball, A. L., 1977, Mineral resources of the Granite Fiords wilderness study area, Alaska, with a section on aeromagnetic data by Andrew Griscom: U.S. Geological Survey Bulletin 1403, 151 p.

  • Deposit

    Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 p., scale 1:250,000.

  • Deposit

    Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

Comments on the references

  • Primary Reference = Berg and others, 1977

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein (Cox and Singer, 1986; model 22c)
Deposit Other Comments = the site is in Misty Fiords National Monument Wilderness.

Reporter information

Type Date Name Affiliation Comment
Reporter 29-JUN-1999 H.C. Berg U.S. Geological Survey