Factors Controlling Tungsten Mobility in Cantung Mine TailingsSoapbox Wednesday, November 21, 2018 - 13:00 to 13:06 Theatre 3
The Cantung Mine in the western Northwest Territories was a leading global producer of tungsten intermittently during the period of 1962 to 2015, and is currently owned by Crown Indigenous and Northern Affairs Canada (CINAC). The mine hosts five tailings ponds (~6.5 Mt total), as well as ~172,000 t of tailings that were deposited directly on the Flat River floodplain during its first three years of production. The tailings vary in terms of their mineralogy and degree of oxidation, which provides an excellent setting to study factors controlling low temperature tungsten mobility. As concerns about tungsten’s potential toxicity have only recently emerged, there is an absence of literature on its fate and transport in the environment. In particular, few studies have addressed tungsten’s mobility in mine tailings, which could act as a large point source of metal leaching.
In July 2018, eleven surface water samples, nine pore-water samples, and seventeen tailings samples were collected from the Cantung Mine’s tailings. The tailings pore-water ranged from being acidic and oxidized (pH = 1.92, Eh = 0.83), to slightly alkaline and reducing (pH = 7.61, Eh = 0.17), and were sampled using suction lysimeters and by centrifuging tailings samples. Tailings samples were also collected from holes that were augered during lysimeter installation. Samples were transported to Queen’s University in Kingston, Ontario, where the water samples have undergone elemental analysis by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), and their anionic composition determined via ion chromatography (IC). Further analyses are planned, including O, H, S, and C stable isotopes, to address specific aspects of tungsten’s behavior in the Cantung tailings. Tailings samples will have their modal mineralogy determined by SEM-MLA, and synchrotron micro-XRD analysis is planned to investigate phase specific adsorption. In addition, solid tailings and their co-existing pore-waters will be used to model water-mineral interactions by running simulations using PHREEQC.