Geoenvironmental characterization of two REE deposits: the Montviel carbonatites and Kipawa silicates, Quebec Canada

Abstract

Drainage water quality is the significant environmental concern for the rare earth elements (REE) mining industry. REE deposits are associated with other metals and radioactive bearing minerals. REE mining and refining activities can generate significant quantities of liquid and solid wastes. Therefore, a long-term integrated approach covering the full mine-life cycle is required to mitigate possible environmental concerns. In the present study, two REE concentrates were prepared and all deposit lithologies of carbonatites and silicates sampled and investigated for their mineralogy, geochemistry, and their environmental behavior using kinetic testing. For the Montviel carbonatite (enriched in light rare earth elements, or LREE), the majority of REE-bearing minerals are associated with carbonates (i.e., monazite, kukharenkoite, burbankite, etc.), whereas the REE-bearing minerals associated with the Kipawa silicates (enriched in heavy rare earth elements, or HREE) are fluorbritholite, eudyalite, mosandrite, etc. The kinetic tests showed a neutral to alkaline pH of leachates and a low leachability of REE (carbonatites <140 μg/L; silicates <15 μg/L) with a higher mobility of HREE than LREE. The reactivity of REE carbonates are one to two orders of magnitude higher than REE silicates. For sustainable mineral development, geological and environmental data was integrated into the geometallurgical model to identify and control the environmental risks associated with mining those two deposits.