• The lithium originates from deep geothermal-magmatic fluids. Lithium isotope data (δ 7 Li values of + 11.51 to + 14.84‰) confirm that Li + is sourced from high-temperature water–rock interactions, where geothermal fluids leach lithium-rich minerals (e.g., lepidolite, feldspar) from the Yanshanian granite at the basin margin and the Zhoutian Formation within the basin. • The brine is formed by mixing of multiple fluid end-members.Hydrogen and oxygen isotope compositions (δD: −53 to −21‰; δ 18 O: −7.8 to −2.4‰) deviate from global/local meteoric water lines and cluster towards a magmatic water field, indicating the brine genesis involves a mixture of magmatic water, meteoric water, and formation water. • Distinct water–rock interactions create an optimal chemical environment for lithium enrichment.Halite dissolution provides a high-salinity (Cl − avg. 188.82 g/L) setting that inhibits Li-mineral precipitation; dolomitization consumes Mg 2+ , resulting in a uniquely low Mg/Li ratio (8–10); and silicate weathering supplements K + , facilitating a “potassium-lithium co-enrichment” characteristic. • Efficient enrichment results from tectonic-climatic synergy.A semi-arid climate drives evaporative concentration, elevating Li + levels (avg. 122.85 mg/L), while basin-controlling faults (e.g., Yongxin-Xiajiang Fault) and the Cretaceous half-graben structure guide and focus the brine into a central depression, where a confined aquifer prevents dilution, forming a high-quality lithium resource. The Cretaceous Zhoutian Formation in the Jitai Basin of Jiangxi Province hosts a high-quality brine-type lithium resource, characterized by high lithium and low magnesium concentrations, which is rarely found in China. The lithium chloride concentration ranges from 308 to 1136 mg/L, with an exceptionally low Mg/Li ratio of only 8–10, indicating significant development potential. However, the lithium material source, enrichment mechanism, and metallogenic model of this brine system remain poorly constrained, hindering regional exploration breakthroughs and the advancement of metallogenic theories. This study systematically investigates the origin and lithium enrichment processes of the deep lithium-rich brines in the southwestern Jitai Basin. A combined approach of hydrochemical analysis and multi-isotope tracing (δD, δ 18 O, δ 7 Li, δ 37 Cl) was applied to 21 deep brine samples. The results showed that the brines have a total dissolved solids (TDS) content ranging from 178 to 592 g/L, pH values between 6.33 and 7.41, and are classified as the Cl − Ca type. The average Li + concentration reached 122.85 mg/L, demonstrating excellent lithium enrichment potential. The dissolution of rock salt and dolomitization were identified as the primary drivers for the evolution of soluble ions in the brine, with silicate weathering also contributing significantly to K + enrichment. Hydrogen and oxygen isotopic compositions suggested that the brine formation involved mixing of magmatic water, meteoric water, and formation water, with the obtained data providing robust evidence for this fluid mixing process. The δ 7 Li values (11.51 – 14.84‰) indicated that lithium in the brine originated from high-temperature water–rock interactions between geothermal fluids and Yanshanian granites at the basin margin, as well as lithium-rich minerals within the Zhoutian Formation. Lithium was leached from mineral lattices and released into the fluid phase δ 37 Cl values (0 – 0.58‰) showed no significant isotopic fractionation, and combined with low Br/Cl ratios, they indicated that Cl - was primarily derived from the dissolution of sedimentary rock salt within the basin. The study ultimately concluded that the efficient enrichment of lithium-rich brine in the Jitai Basin resulted from the coupled interaction of four key processes: lithium supply from deep geothermal-magmatic fluids, optimization of the metallogenic environment through water–rock interactions, lithium concentration enhancement via evaporative concentration, and ore preservation controlled by the tectonic system. This study establishes a metallogenic model for lithium-rich brines in the Jitai Basin, deepening the understanding of brine-type lithium mineralization in continental basins of South China and providing broad guidance for lithium exploration in similar basins across southern China.
Pan et al. (Wed,) studied this question.