Gemini

Prospect, Active

Alternative names

South Vein

Commodities and mineralogy

Main commodities Ag; Sn
Other commodities As; Cu; Fe; Pb; Sb; W; Zn
Ore minerals arsenopyrite; cassiterite; chalcopyrite; sphalerite
Gangue minerals axinite; quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale B-6
Latitude 63.498
Longitude -155.671
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

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 plutonic 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.
Geologic map unit (-155.673365574724, 63.4973926013536)
Mineral deposit model Tin-polymetallic veins (Cox and Singer, 1986; model 20b).
Mineral deposit model number 20b
Age of mineralization Late Cretaceous-Early Tertiary age, based on radiometric ages of related plutonic rocks in Kuskokwim Mineral Belt (Bundtzen and Miller, 1997).
Alteration of deposit Axinite-sericite-tourmaline replacements.

Production and reserves

Workings or 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.
Indication of production None
Reserve estimates 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.

Additional comments

See: Won - South (MD024), Win (MD060), Won - North (MD021) and Cloud (MD059) prospects.

References