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Open-File Report 02-010

Version 1.0

Case Study of the Environmental Signature of a Recently Abandoned, Carbonate-hosted Replacement Deposit: The Clayton Mine, Idaho

By J. M. Hammarstrom, R.G. Eppinger, B.S. Van Gosen, P.H. Briggs, and A.L. Meier

U.S. Geological Survey Open-File Report 02-010 in Adobe Portable Document Format (PDF):

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Clayton mine is a silver-lead-zinc replacement deposit in the Bayhorse mining district in Custer County, Idaho. The deposit is hosted by dolomite and quartzite within a fault-bounded block of Paleozoic rocks east of the Idaho batholith. The mine was discovered in 1877, developed as an underground mine, and produced silver (218,692 kg), lead (39,358,903 kg), zinc (12,778,700 kg), copper (754,858 kg) and minor gold. Cobalt is also reported. The mine operated from 1935 to 1986. The geology of the area and descriptions of the 1920's- era workings are given. The mine was last operated by Clayton Silver Mines, Inc. through 1986. The modern mill at the mine site is along Kinnikinic Creek, which drains into the Salmon River at Clayton, about 1.5 miles (2.4 km) downstream from the mine. The mill produced a lead concentrate by selective flotation that contained 35 to 45 percent lead and 3,400 to 6,800 g/t silver. Mill tailings were placed as terraces along steep slopes within the narrow stream valley, extending to the edge of creek. Prior to the most recent mining activity, a historic smelter, on the north bank of the Salmon River at the town of Clayton, processed ores from a number of mines in the district and dumped slag directly into the river. The smelter operated intermittently from the 1880s to 1902. The U.S. Environmental Protection Agency (EPA) and the U.S. Bureau of Land Management (BLM) have been investigating environmental issues related to the abandoned mine site since the early 1990s. In October, 2001, EPA completed a Time-Critical Removal Action to stabilize mine tailings to prevent erosion into Kinnikinic Creek, to control infiltration of water into tailings and seepage of water from tailings, and to minimize wind erosion.

Contact: J.M. Hammarstrom

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