Abstract
The Cantung mine is a formerly operating tungsten mine located in the Nahanni area of the western Northwest Territories. As part of the Northern Abandoned Mine Reclamation Program, the Canadian government is looking to remediate the property This may include reprocessing the tailings to isolate potentially acid generating sulphide minerals, in order to mitigate any possible environmental liability to the nearby Flat River and its confluences. Cantung’s mineral processing operations produced three concentrates and one tailings product: a high-grade WO3 concentrate, medium grade WO3 concentrate, a copper concentrate and sulphidic tailings. During periods of low copper prices, chalcopyrite was not recovered from the ore, and instead reported to tailings. Poor recovery from the scheelite gravity separation circuit combined with intermittent chalcopyrite flotation has resulted in the tailings containing notable quantities of copper and tungsten, which could be recovered during reprocessing to offset costs. Experimental work was completed on tailings samples collected from tailings pond 3, Cantung’s largest impoundment. Ideal flotation conditions were determined to remove potentially acid generating minerals (mainly pyrrhotite) while also recovering residual valuable minerals, primarily chalcopyrite. A polish grind of the tailings sample prior to flotation was found to increase sulphide mineral recovery. Up to 86% of sulphur and 84% of copper were concentrated into 30% of the sample mass using flotation, while between 80% and 95% of tungsten reported to the sulphide flotation tailings. Investigation into collector and dispersant dosages in mixed xanthate-hydroxamic acid collector system was determined using a design of experiments, which identified the optimal conditions for sulphide mineral recovery from the tailings. Future research will focus on the development of a flowsheet to further upgrade copper from the sulphide fraction and to recover tungsten from the sulphide flotation tailings.