A world class geothermal lithium resource in the Cooper Basin Region, South Australia: potential for enhanced domestic energy security using sustainable production methods

Australia supplies approximately 35% of global lithium feedstock via spodumene production, yet exports around 95% for processing, primarily to China. This creates potential supply chain vulnerabilities as lithium demand surges. The Cambro-Ordovician Warburton Basin underlying the Cooper Basin in northeastern South Australia is intruded by Carboniferous-aged, radiogenic granites of the Big Lake Suite (BLS) up to 12 km thick. These granites reach 250°C and 73 MPa at depths of approximately 4 km. Cooling joints, faults and fractures within the granite have enabled pervasive hydrothermal alteration, enriching formation fluids with lithium and other critical minerals such as rubidium and caesium. More than 100 fluid samples from five deep wells penetrating the BLS granite across the Nappamerri Trough show consistent chemistry, with measured lithium concentrations up to 320 mg/L and averaging ≈240 mg/L (excluding heavily diluted samples), total dissolved solids below 20,000 mg/L and negligible magnesium and sulfate. This makes the fluid highly favourable for large-scale, low-cost Direct Lithium Extraction. The BLS granite has a JORC-compliant (Joint Ore Reserves Committee) inferred resource of 25.2 Mt lithium carbonate equivalent, ranking it among the world’s largest known lithium brine resources. Testing of historic geothermal wells demonstrates high flow and injection rates, indicating well-developed fracture permeability and a regionally connected system. This unique basement-hosted geothermal lithium resource offers the potential for multi-generational, low-emission production powered by co-produced geothermal energy providing Australia with a strategic pathway to develop a domestic battery-grade lithium supply chain while strengthening energy security.