Sediment contributions to lithium enrichment in basinal brines: A case study from the Duperow Formation, southeastern Saskatchewan

Increased demand for lithium (Li) in renewable energy technologies has driven exploration for new deposit types, including basinal brines such as those of the Devonian-aged Duperow Formation of the Williston Basin (western Canada). Although interest in Li resources across North America is rapidly increasing, the mechanisms which generate brines with economic Li concentrations remain under-constrained. This study seeks to examine the role of sediment contributions for Li to basinal brines, focusing on the Duperow and the overlying Birdbear and underlying Souris River formations. Leaching experiments on clay-rich intervals from these formations indicated that elevated temperatures and calcium (Ca) and magnesium (Mg) concentrations resulted in enhanced Li liberation, and leaching efficiency was positively correlated with higher clay-mineral and dolomite content, indicating a probable mineralogical control. This implies that diagenetic processes, such as dolomitization and illitization, may promote Li release from shales. The leaching experiments formed the basis for Monte Carlo simulations, which suggest that the sediments may provide a sufficient source to account for the elevated Li concentrations in Duperow Formation brines. Together, these results demonstrate that Li-rich brines may be sourced locally through diagenetic processes involving Li-rich clay minerals. This work supports the development of a mineral-systems approach to better understand the genesis of basinal brine-hosted Li deposits, an unconventional resource poised to play an increasingly important role in meeting Li demand. • Increasing solution temperature and Ca concentration results in greater Li leaching. • Dolomite-, clay-mineral content positively correlated with Li leaching. • Illitization, dolomitization may be crucial for Li release from source rocks. • In-situ water-rock interactions likely key in generation of Li-rich basinal brines