Effect of Temperature on the Weathering of Various Waste Rock Types from the Raglan Mine

The Raglan Mine (Xstrata Nickel) is located in the Nunavik region of the province of Quebec (62°N). At the mine site, the permafrost has a depth of 586 meters and a minimum temperature of -6.9°C. Some waste rock has been identified as having nickel leaching potential, while the rehabilitation concept for mine rock is based on permafrost temperatures. Seven rock types were studied to investigate the effect of temperature on mine rock weathering. The rock was characterized and subjected to kinetic tests at different temperatures. Tests were performed at 22, 10, and -6°C and with alternate cycles of freezing and thawing. The results showed that sulphide oxidation and silicate dissolution rates decrease with temperature following an Arrhenius-like response. Nickel can be leached from the rock in response to sulphide mineral oxidation and by the dissolution of secondary minerals precipitated on the rock surface. However, nickel was also retained in the solid phase by sorption and precipitation mechanisms at all temperatures. This investigation showed that temperature influences the geochemical behavior of Raglan waste rocks in kinetic tests and that integrating this parameter in predictive tests would help to obtain more realistic water quality predictions.