DIAVIK TEST PILES PROJECT: EARLY STAGE GEOCHEMISTRY AND MICROBIOLOGY

摘要

Environmental concerns arise as a result of mining and mineral processing. With agrowing mining industry in northern Canada, there is an increased demand forinformation pertaining to long term environmental impacts in the Arctic, where uniqueclimatic and physiographic conditions exist. Sulfide mineral oxidation is catalyzed bybacteria including Acidithiobacillus and Leptospirillum species and results in thegeneration of acidic drainage. Little is known, however, about the biogeochemicalevolution of waste rock and the rate of sulfide oxidation in regions with continuouspermafrost. A collaborative research project was initiated to examine the quality ofdrainage emanating from waste rock piles and the role of bacteria in the biogeochemicalevolution of waste rock effluent water. Diavik diamond mine is located 300 km north ofYellowknife, Northwest Territories on a 20 km~2island in Lac de Gras. Waste rockgenerated from the open pit mine operation is stockpiled on site and at mine closure willconsist of two 200 Mt waste rock stockpiles. Waste rock at Diavik consists of graniteand pegmatite containing irregular laths of biotite schist. These host rocks are cut byintrusions of diabase. Because the distribution of the biotite schist is unpredictable, thewaste rock at Diavik is segregated into three categories, Type I rock, principally granite,contains <0.04 wt.% S, Type II rock which contains some biotite schist contains 0.04 to0.08 wt.% S, and Type III rock with a greater proportion of biotite schist contains >0.08wt% S. All rock types contain low concentrations of carbonate minerals (Blowes et al.,2006). Three waste rock test piles were constructed at Diavik. The first pile wasconstructed with <0.04 wt% S waste rock (Type I pile), while another pile (Type III pile)was constructed with >0.05 wt% S waste rock which is a mixture of Type II and Type IIImaterial. The Covered pile was constructed based on the mine closure plan whichincludes a Type III core covered with a lm layer of till and 3m of Type I waste rock.Due to the extremely cold temperatures in this region the rates of sulfide oxidation anddissolution and metals release are uncertain.