Independence Mine

Mine, Active

Commodities and mineralogy

Main commodities Au
Other commodities Ag; As; Hg; Pb; Sb; Sn
Ore minerals arsenopyrite; chalcocite; chalcopyrite; cinnabar; gold; magnetite; pyrite; stephanite; stibnite
Gangue minerals quartz; siderite

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-1
Latitude 62.9442
Longitude -156.4772
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Independence Mine is on a northwest-trending ridge about 2.2 miles southwest of the junction of Ganes Creek and Six Gulch. It is at an elevation of about 1740 feet near the southwest corner of section 15, T. 33 N., R. 38 W., of the Seward Meridian. The mine is accurately located.

Geologic setting

Geologic description

The deposit at the Independence Mine as a quartz-carbonate-sulfide vein about 1.5 to 3 feet thick on the hanging wall of an altered composite andesite-granite porphyry dike. According to Eakin (1914) the vein exposed in underground workings averaged about 2 feet thick. The dike strikes N55-70E and dips steeply SE. The granite porphyry which may be dominant phase averages about 32 feet thick and can be traced in rubble for about 1,000 feet. The altered andesite phase is exposed in trenches above the underground workings (Bundtzen and Laird, 1982).
About 1 to 5 percent sulfides, principally arsenopyrite, pyrite, and stibnite and minor cinnabar and stephanite, are disseminated in the vein and adjacent dike rock. Gold occurs in iron-stained crevices and vugs in quartz. Eakin (1914) reported microscopic native gold embedded in magnetite in vein material. Grab samples of the vein reported by McGimsey and others (1988) and Bundtzen and Miller (1997) contained up to 180.0 parts per million (ppm) gold, 13.0 ppm silver, 2.10 percent arsenic, 20 ppm bismuth, 0.56 percent antimony, more than 10.0 ppm mercury, 1,500 ppm lead, and 300 ppm tin.
The vein was developed by an adit and possibly several hundred feet of inclined and level workings. About 470 tonnes of ore mined in 1911 and 1912 produced 479 ounces of gold.
The Independence deposit is similar to other gold-polymetallic veins along the Ganes-Yankee Creek fault and dike swarm (Miller and Bundtzen, 1994; Bundtzen and Miller, 1997). Anomalous tin is present at the Independence Mine, and is known elsewhere in the region in rocks about 70 Ma, for example in felsic plutonic rocks at Donlin Creek prospect (ID167). Mineralization at the Independence and nearby deposits along the Ganes-Yankee Creek fault and dike swarm has been compared to the Donlin Creek mineralization by Miller and Bundtzen (1988) and Bundtzen and Miller (1997).
Warren Magnuson explored the mine area with trenches and open cuts in the 1960s and 1970s. Westgold explored the area in the early 1990s. Placer Dome Exploration conducted a detailed soil survey over the Independence Mine and drilled two core holes totaling about 500 feet in 1996-97 (St. George, 1998). Although the full details of the Placer Dome Exploration exploration are not available, gold-bearing veins are known to have been intersected below the mine workings.
In early 2010, the property was owned and operated by Clark-Winze Mining (Grady, 2009). In 2007 and 2008, Great Basin Gold Ltd. explored the property after compiling the work from the six exploration groups who had worked on the property since 1988. Their work consists of more than 32,000 meters of trenching and continuous chip sampling of the trenches, as well as 83.6 line miles of IP, TMF, and HLEM ground geophysical surveys.
As described by Grady (2009), the Independence Mine and a newly discovered prospect on Potosi Ridge (ID181), are in the cores of major northeast-striking antiforms in Cretaceous Kuskokwim Group flysch. The hinges of the antiforms are thickened and marked by chevron folding and high angle faulting. In some cases, the cores of the some of the antiforms are deformed into brittle melange. The prospects are associated with northeast-striking swarms of mafic to granitic dikes and older biotite granodiorite to aplite sills. The dike swarms have been offset by numerous north-northwest high-angle faults and joints and often have marginal dip-slip faults.
The mineralization is marked by quartz-carbonate veins along fractures. The veins typically have early quartz-carbonate margins and later cores of clear to white quartz and carbonates. Occasionally, the veins contain late-stage gold and quartz, with iron carbonate and sericite. Sparse pyrite and arsenopyrite occur in the veins and wall rock. Rare, chalcopyrite, galena, and chalcocite are present in the high-grade veins. Samples from a 2-inch-wide quartz vein that extends for 6 meters along dip at the mine contained 592 to 2,140 ppm gold.
3D modeling of gridded IP surveys show that anomalies are associated with high copper, nickel, lead, and zinc values. Resistivity data outlines the the dike swarms; ground magnetic highs correspond to felsic intrusives and magnetic lows outline silicification and brecciation.
Geologic map unit (-156.479564566468, 62.9435669098317)
Mineral deposit model Low sulfide gold-quartz vein (Singer and Cox (1986) model 36a).
Mineral deposit model number 36a
Age of mineralization The granite-porphyry dike at the Independence Mine has been dated at 70.4 Ma (T.K. Bundtzen, unpublished data, 1998).
Alteration of deposit Local silicification and development of siderite and other carbonate minerals in an altered dike; secondary oxidation.

Production and reserves

Workings or exploration
According to Eakin (1913), the underground work during 1912 consisted of a 60-foot adit, a 60-foot winze driven at the end of the adit, and two drifts about 30 and 50 feet long. The equipment at the mine site included a 12-horsepower engine and a Little Giant crusher and stamp mill. In 1979, the portal's entrance had caved and exposed the winze. Remnants of the stamp mill are about 650 feet south of the underground workings in a unnamed gulch.
Warren Magnuson explored the mine with trenches and open cuts in the 1960s and 1970s. Westgold explored the area in the early 1990s. Placer Dome Exploration conducted a detailed soil survey over the Independence Mine and drilled two core holes totaling about 500 feet in 1996-97 (St. George, 1998).
In early 2010, the property was owned and operated by Clark-Winze Mining (Grady, 2009). In 2007 and 2008, Great Basin Gold Ltd. explored the property after compiling the work from the six exploration groups who had worked on the property since 1988. Their work consists of more than 32,000 meters of trenching and continuous chip sampling of the trenches, as well as 83.6 line miles of ground IP, TMF, and HLEM geophysical surveys.
Indication of production Yes
Reserve estimates None published.
Production notes The only production was in 1911 and 1912 when the Carter Creek Mining Company produced 479 ounces of gold from the underground workings.

References

References

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., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Grady, Jesse C., 2009, High-grade structurally controlled gold veins at Ganes Creek, Ophir mining district, southwestern Alaska: Abstracts, Alaska Miners Association, 2009 Annual Convention, p. 15-16. (As of Feb 2, 2010, on the Internet as: http://www.alaskaminers.org/abstracts2009.pdf).
Hollister, V.F., 1992, On a proposed plutonic porphyry gold deposit model: Nonrenewable Resources, vol. 1, p. 293-302.
St. George, P., 1998, Progress report for 1997, Ganes Creek project A326, southwest Alaska: Anchorage, Alaska, unpublished Placer Dome Exploration report, 13 pages, plus plates and appendices.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); C.C. Hawley (Hawley Resource Group); D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010