LITHIUM SOURCES AND ENRICHMENT MECHANISMS FOR THE LITHIUM-RICH OIL FIELD BRINES OF THEDEVONIAN NISKU, LEDUC, AND SWAN HILLS FORMATIONS

North American lithium resources are pivotal to the clean energy transition and national security. The low-temperature geothermal brines of the Devonian Alberta Basin, Canada are quickly emerging as an unconventional domestic lithium resource. This study integrates publicly available and new geochemical data on Devonian Nisku, Leduc, and Swan Hills Formation brines to investigate brine origin and evolution, and lithium sources and enrichment mechanisms. The brines are stratigraphically and spatially heterogeneous, suggesting a complex brine evolution history. We interpret the Nisku Formation waters as primary brines (evapoconcentrated seawater) and the Swan Hills Formation waters as secondary brines (dissolution of halite); both show higher lithium concentrations in excess of seawater evapoconcentration to halite saturation and beyond, suggesting there must be additional sources of lithium to the system. We observe that brine lithium isotopic signatures and lithium concentrations are consistent with average global marine shales. Our results show that rock-water interactions with the encasing Devonian marine shales are a possible source of lithium. In contrast to recent work on the Upper Devonian Leduc Formation brines, our study finds the Swan Hills and Nisku Formations’ brines show more spatial heterogeneity. Despite geochemically distinct brines, we see evidence for brine interaction with shales is strong in all three units. Characterization of lithium-enriched low temperature brines will support North American lithium exploration by better informing lithium resource estimates, and aiding the development of more sustainable lithium extraction methods.