Geoenvironmental characteristics of Canadian critical metal deposits

Abstract

In recent years, there has been a rapid increase in the global demand for many elements used in high-tech, environmental, and/or defense applications, including antimony (Sb), cobalt (Co), indium (In), lithium (Li), niobium (Nb), rare earth elements (REE), and tungsten (W). These elements are used in a broad range of devices, including hybrid vehicles, photovoltaic cells, clean energy lighting, rechargeable batteries, mobile phones, LCD screens, and wind turbines. The term "critical metal" has been used to designate elements that are deemed essential, but whose supply is at risk because of rapid growth in demand, scarcity, political control of exports, low recycling rates, or concerns over the environmental impacts of mining (NRCan 2015). Of all critical metals, the supply of REE is currently deemed to be most at risk because of rising global demand and recent restrictions on exports from China. Likewise, the demand for Nb is predicted to rise faster than most other elements over the next decade (>8% per annum) because of its importance in producing high-strength, low-alloy steel (EU 2014). Canada has abundant reserves of both REEs and Nb and there are currently numerous exploration projects underway across the country and several projects at the environmental assessment stage. However, our understanding of the environmental characteristics of critical metals is immature compared to that for other commodities (e.g., Au, Cu, Pb, Zn, U). Detailed geoenvironmental studies of Canadian critical metal deposits are required to assess the environmental risks associated with these resources, and to mitigate the impacts of future development activities. This activity will provide geochemical and mineralogical data and knowledge of key geological processes controlling the environmental signature of carbonatite-hosted Nb and REE deposits. Field activities will be conducted at the former St. Lawrence Columbium Mine in Oka, QC, which is enriched in REEs and was a major Nb producer from 1961 to 1976. Research will focus on understanding groundwater-tailings reactions that control the mobilization of trace metals (Nb, REE, U, Th) and radionuclides (Ra-226, Pb-210) in seepage from mine tailings, and on the processes that control the cycling of these elements in flooded pit lakes. Outputs from this work will provide new information that can be used to assess, monitor, and manage mining impacts, and help to establish Canada as an environmentally responsible supplier of critical metals.