Calcium-Rich Lithium Brines of the Maricunga Salar, Chile: Resource Potential, Processing Challenges and Future Sustainable Projects

Chilean lithium production depends on the Atacama Salar, and the Atacama Region is the main option for diversifying it. Published geological, hydrogeological, geochemical, technological and institutional information on the Maricunga Salar is integrated here; most project-scale data derive from one NI 43-101 technical report. Brine chemistry determines how lithium can be processed, and reservoir properties determine how much brine can be extracted. Maricunga brines average 1122 mg/L Li (range 460 to 3375 mg/L; n = 718), with a mean total dissolved solids content of 311 g/L, Mg/Li of 6.53 (equal to that of Atacama), Ca/Li of 11.45 and SO4/Li of 0.63, and, with Tres Quebradas (Argentina), define the calcium-rich endmember of the Andean brines compiled. Pitzer calculations place the mean brine at gypsum saturation, and simulated evaporation removes only about 1% of the calcium, so calcium must be removed chemically in addition to magnesium (2.2 t Ca and 1.2 t Mg per tonne of lithium carbonate equivalent, LCE). In the reservoir, drainable porosity ranges from 0.02 in the lacustrine clays separating the shallow and deep aquifers to 0.14 in marginal alluvial deposits, and the coarse units holding most drainable brine are the least sampled. Resource estimates evaluated different areas and depths and are not directly comparable: 224,300 t Li in 1982 (0 to 30 m) and 358,000 t Li in 2021 (0 to 400 m, 953 mg/L). Announced projects total 75,000 t LCE/year in their initial stages. The main constraints are hydrogeological and institutional: unresolved connectivity with Laguna Santa Rosa and the Paipote ravine, unpublished hydraulic conductivity and piezometric data, and undemonstrated calcium removal and spent-brine reinjection at industrial scale.