Integrating brine geochemistry and basins analysis to identify favorable target areas for lithium extraction from brines in the contiguous United States

Lithium is designated as a critical mineral by the U.S. Government and is essential for several strategic applications. Dissolved lithium can be commercially extracted from subsurface brines; however, recovery efficiency is strongly influenced by where elevated concentrations of interfering cations can compete with Lithium during extraction increasing operational costs. Using the U.S. Geological Survey National Produced Waters Geochemical Database (v. 3.0), we evaluate produced water lithium concentrations alongside the most problematic co-occurring cations to assess compositions expected to be most amenable to efficient extraction. A brine suitability index was developed that integrates lithium concentrations with weighted contributions from interfering cations based on their relative impact on extraction. We combined this brine suitability index with a spatial clustering analysis to identify statistically significant groupings of reservoirs with favorable producibility indices to delineate laterally continuous lithium-rich exploration targets. Favorable target areas were identified in multiple basins and geochemical cross-plots were used to evaluate lithium behavior relative to salinity and to identify lithium enrichment influenced by marine brine interaction with volcanic rocks. Results indicate a continuum of suitable lithium-rich brines ranging from high-salinity, evaporite- and seawater-derived brines in carbonate platforms to lower-salinity brines, in which lithium enrichment is decoupled from chloride concentrations and is more influenced by water–rock interactions. Combined with analysis of the lithology and basin history of each favorable target area, these observations support a lithium system model in which lithium is: 1) sourced conservatively from evaporated or recycled marine brines and/or added through brine interaction with lithium-bearing silicates, clays, and organic-rich shales; 2) transported with basinal fluids generated during compaction and migrating under regional flow regimes; 3) concentrated where reservoirs are hydraulically isolated by low-permeability seals; and 4) preserved where subsequent flushing/dilution is limited and preserved high salinity conditions inhibit lithium sorption, ion exchange, or precipitation.