POST-MINE METAL TRANSPORT AND ATTENUATION IN THE KENO HILL MINING DISTRICT, CENTRAL YUKON, CANADA

The Keno Hill mining district in central Yukon was the second largest silver producer in Canada with mines operating from 1913 to 1989 on mo re than 65 vein silver deposits. The seven and a half decades of minin g activities have generated large volumes of mine waste disposed on th e land surface, resulting in elevated metal contents in numerous small drainages. To assess the extent of metal mobilization, old mine worki ngs and the associated mine waste were examined and the water courses draining to a major river valley sampled. The results of field observa tions and an array of water and sediment analyses led to three major c onclusions. 1. Acid mine drainage is not widespread because of galvani c protection of pyrite from oxidative dissolution and neutralization b y carbonates in the country rock. 2. Mechanisms operative to limit aqu eous metal transport in small streams in the district include cryogeni c precipitation, coprecipitation and sorption. 3. The near-surface con centration of metals limits the options of waste disposal in future mi ning developments due to potential metal-leaching problems.