TOWARDS DEVELOPING AN EXPLORATION MODEL FOR LITHIUM IN SEDIMENTARY BASIN BRINES: IDENTIFICATION OF THE LITHIUM SOURCE

The surge in lithium demand stemming from its role in the energy transition will require the development of new sources to meet the impending supply gap. Most promising among these new sources are sedimentary clay deposits and deep subsurface brines from sedimentary basins, also referred to as petro-lithium. In the Western Canada Sedimentary Basin, brines hosted in Frasnian-aged carbonate aquifers host significant mineral resources, with current estimated indicated and measured resources exceeding 20M tonnes/LCE. However, this exploration has been limited to areas where there is existing data from producing hydrocarbon or water source wells. Accordingly, there could be other areas or intervals which were not prospective for hydrocarbons, but could be for lithium, however assessing the lithium potential of new targets without having a fluid sample is extremely difficult.

This research investigates the variables involved in creating a deposit model for subsurface brines in the WCSB, which can be used to aid exploration into new areas within the basin. One of the first steps in developing such a model is identifying the lithium source. Previous work has postulated that the lithium rich brines are generated through either seawater evaporation, evaporite dissolution, or contributions from the Precambrian basement. However, there is a growing body of evidence indicating the lithium is derived from in-situ water-rock interactions; analogous to continental brine deposits. This includes the presence of Li-rich clay intervals, isotopically heavy δ¹⁸O and light δ⁷Li signatures indicative of water-rock interactions, and enhanced leaching of the clays under the geochemical and temperature conditions specific to these Frasnian aquifers. Additionally, stratigraphic and hydrogeological controls including the flow rate and a trapping mechanism also play a role in creating these lithium-rich brines which could be a major source of global lithium.