Spatial variations and controls of acid mine drainage generation

Abstract.

Spatial variations of historical and ongoing pyrite oxidation rates were quantified near the Nanisivik Mine on Baffin Island in northern Canada. The variations observed depend mainly on the degree of water saturation, pH and temporal trends in mineral reactivity. Maximum oxidation rates were observed in an untreated tailings spill, while minimum oxidation rates were noted for tailings deposited under water. Spatial trends in oxidation rates were in the order of three orders of magnitude. Spatial trends were only possible to quantify by a combination of closed chambers (well-drained conditions) and micro sensors (water-covered conditions). Oxygen uptake rates in tailings at various ages (up to 7 years) indicate a decrease by more than a factor of 3 over time. Total oxygen uptake over 7 years was calculated and found to be in a fair agreement with the overall pyrite depletion evaluated as high-resolution mineral mass balance (by quantitative powder X-ray diffraction).