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Gemini

Prospect in Alaska, United States with commodities Silver, Tin, Arsenic, Copper, Iron, Lead, Antimony, Tungsten, Zinc
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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. 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 10308644
Record type Site
Current site name Gemini
Alternate or previous names South Vein

Geographic coordinates

Geographic coordinates: -155.67399, 63.49747 (WGS84)
Relative position The Gemini (South Vein) prospect, which is considered a part of the larger 'Won' mineralized system, is situated near the top of a north-south trending ridgeline at an elevation of 2,500 feet (762 m) in Section 18, T. 23 S., R. 17 E., of the Kateel River Meridian. The Gemini prospect is approximately 1.5 miles (2.4 km) northeast of the Won-South prospect. (MD024).

Site location context

Political divisions (FIPS codes)

Yukon-Koyukuk(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Medfra B-6(quadrangle 1:63,360 scale)

Medfra S(quadrangle 1:100,000 scale)

Medfra(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Tin Critical Primary
Arsenic Critical Secondary
Copper Secondary
Iron Secondary
Lead Secondary
Antimony Critical Secondary
Tungsten Critical Secondary
Zinc Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Cassiterite Ore
Chalcopyrite Ore
Sphalerite Ore
Axinite Gangue
Quartz Gangue
Tourmaline Gangue

Alteration

  • Axinite-sericite-tourmaline replacements.

Mineral occurrence model information

Model code 77
USGS model code 20b
Deposit model name Sn-polymetallic vein

Nearby scientific data

(1) -155.67399, 63.49747
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The Gemini prospect consists of three, closely spaced, North 65 degree West-trending breccia veins that cut thermally altered Upper Cretaceous, Kuskokwim Group flysch. The vein deposits consist of crackle breccias and limonitic brecciated hornfels that contain massive to disseminated cassiterite, arsenopyrite, chalcopyrite, and sphalerite. Cassiterite-bearing veins can be traced east of the ridge summit, but not to the west. The Gemini Vein has a minimum strike length of 900 feet (275 m), whereas the South Vein could be traced for about 4,300 feet (1,310 m). The Gemini prospect is inferred to be Late Cretaceous-Early Tertiary age, based on radiometric ages of related pluronic rocks in Kuskokwim Mineral Belt (Bundtzen and Miller, 1997). A 1984 Anaconda Minerals Company drill program encountered up to 8.15 percent tin and 3.91 ounces/ton silver over widths of 1.5 feet (0.45 m) in the Gemini vein.
  • Age = Late Cretaceous-Early Tertiary age, based on radiometric ages of related plutonic rocks in Kuskokwim Mineral Belt (Bundtzen and Miller, 1997).

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Active

Mining district

District name Innoko

Comments on the reserve resource information

  • Reserves = Based on Anaconda Minerals Company exploration data and their own surface sampling, Burleigh (1992 BMOFR 85-92) and Bundtzen and Miller (1997) estimate that 1,153,333 tons (1,046,300 tonnes) of ore contains 0.216 percent tin. The average tenor for other metals (silver, arsenic, lead, tungsten, antimony, and zinc) was not calculated.

Comments on the workings information

  • Workings / Exploration = A data release from the U.S. Geological Survey AMRAP survey of the Medfra quadrangle (King and others, 1980; Patton and others, 1980) indicated that anomalous tin, tungsten, bismuth, lead, silver, and arsenic were detected in stream sediment and pan concentrate samples draining the Gemini prospect area. Duval Corporation and Anaconda Minerals Company followed up on this work and discovered the Gemini and related vein systems. In 1984, Anaconda Minerals Company completed three shallow diamond drill holes into the Gemini and South Veins. The Anaconda Minerals Company drill program encountered up to 8.15 percent tin and 3.91 ounces/ton silver over widths of 1.5 feet (0.45 m). Online Exploration Services Inc. (Anchorage, Alaska) explored the property in 1997.

Reference information

Bibliographic references

  • Deposit

    Patton, W.W., Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-A, 1 sheet, scale l:250,000.

  • Deposit

    Burleigh, R.E., 1992, Tin mineralization at the Won prospect, west-central Alaska: U.S. Bureau of Mines Open-File Report 85-92, 19 pages.

  • Deposit

    Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Economic Geology Monograph #9, Mineral Deposits of Alaska, p. 242-286.

  • Deposit

    King, H.D., Risoli, D.A., Cooley, E.F., O'Leary, R.M., Speckman, W.A., Speisman, D.L., and Galland, D.W., 1980, Final results and statistical summary of analyses of geochemical samples from the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811F, 134 pages.

Comments on the references

  • Primary Reference = Burleigh, 1992 (BMOFR 85-92)

General comments

Subject category Comment text
Deposit Model Name = Tin-polymetallic deposits (Cox and Singer, 1986; model no. 20b)
Deposit Other Comments = See Won - South (MD024), Win (MD060), Won - North (MD021) and Cloud (MD059) prospects.

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUN-1998 Bundtzen, T.K. Pacific Rim Geological Consulting

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.