Abstract
Mineral resources extraction, especially by open-pit mining techniques, produces significant amounts of waste rock worldwide, large volumes being stored in piles on site. Nonetheless, the recovery of non-hazardous waste rock for road construction can reduce the environmental footprint of mining activity by limiting the supply of borrow materials and the use of natural resources. Moreover, by reducing waste pile size, long-term waste and drainage water management are minimized, and landscape visual alteration is limited on mining sites. This approach is thus positive in both the perspective of circular economy and sustainable mining. However, prior to valorizing the waste rock, mining companies must perform an environmental assessment. In the context of the development of the Authier lithium mining project (Québec, Canada), environmental geochemical characterization of some rock waste was performed. The environmental study included the inventory of major minerals, chemical characterization, and a series of leaching tests recommended in Québec: standardized leaching tests, sequential extractions and kinetic tests under laboratory and field conditions. Rock sampling was conducted across drill cores to address selected lithologies and thereafter composite samples were prepared, representative of the South, North, West, and Center of the mineralized zone, in agreement with the planned development of the future mine. The results showed that the samples studied were non-acid generating. Potential contaminants As, Sb, Cu, Pb, Zn were found in low contents, whereas Al, Cr, Fe, Mn, Ti, V, Ni were found in significant contents in rock samples. Among these metals, Ni and Cu were found potentially leachable. Consequently, the valorisation of the waste rock for roads or construction material was not considered for now. However, the knowledge acquired through this study is useful for the mine development and post-closure restoration of the future Authier lithium mine.