Lithium Distribution and Hydrogeochemical Associations in Contrasting Waters of the Mangystau Region, Kazakhstan

Lithium (Li) occurrence in the Mangystau Region of western Kazakhstan has been investigated primarily in deep formation and oilfield brines, whereas surface waters and shallow groundwater remain poorly characterized. This study aimed to establish a regional hydrochemical baseline by examining Li distribution and its associations with major-ion composition across contrasting water types. In May 2026, water samples were collected from 14 sites, including saline lakes, sors (salt-flat depressions), river reaches, groundwater wells, and a thermal spring. Eight sites were resampled on 30 August 2026; the remaining six were dry or inaccessible. Major ions were determined using titrimetric, turbidimetric and ICP-OES methods, with Li, Na, and K quantified by ICP-OES. Hydrochemical associations in the May dataset (n = 14) were evaluated using Spearman rank correlations, permutation tests, and Benjamini–Hochberg false-discovery-rate (FDR) correction. Li+ concentrations ranged from 0.08 to 0.82 mg L−1 in May and from 0.25 to 2.29 mg L−1 in August. Concentrations were higher in August at seven of the eight resampled sites. Kishi Oymasha exhibited the highest calculated total dissolved solids (TDS ≈ 275 g L−1) but contained only 0.31 mg L−1 Li+, an indicative value because matrix-specific validation of Li+ was not performed for the samples with TDS > 100 g L−1. After Benjamini–Hochberg FDR correction of the permutation p-values, significant positive associations with Li+ remained for Cl−, Na+ + K+, SO42−, and TDS; however, none remained significant when the five May samples with indicative Li+ results were excluded (n = 9). Positive correlations with Ca2+, Mg2+, and total hardness were also observed but were not statistically significant after this correction. These findings suggest that salinity alone does not adequately explain Li distribution. Evaporative concentration, differences in Li supply, hydrological mixing, and water–rock interaction remain competing or complementary hypotheses requiring further investigation using isotopic tracers and site-specific hydrological data.