<p>The shallow-buried brines in Bankog Co Salt Lake (BCSL) are characterized by high total dissolved solids (TDS) and K, Li, B, Br concentrations, which is apparently different from the lake waters’, indicating great potential of exploitation. The hydrochemistry and formation of these shallow-buried brines are still mysterious. We collected 17 shallow-buried brine samples, and 4 lake brine samples from various locations in BCSL, and conducted elemental and D-O (deuterium, also known as heavy hydrogen and oxygen) isotopic analysis to clarify the solute sources and formation mechanisms of the shallow-buried brines. Results reveal that: (1) the shallow-buried brines are highly mineralized Na-Cl type brines, rich in Na⁺, Cl⁻, K⁺, CO<Stack> ₃ ²⁻ </Stack>, and SO<Stack> ₄ ²⁻ </Stack> but poor in Ca²⁺ and Mg²⁺. Concentrations of trace elements such as Li⁺, B³⁺, and Br⁻ are significantly higher than those in lake brines, and most exceed industrial mining thresholds; (2) the shallow-buried brines showed uneven spatial distribution, with high-concentration zones concentrated in the lake basin center and marginal areas significantly influenced by river dilution, providing spatial guidance for resource exploration and development; (3) D-O isotopes indicate that the brines originated from evaporated meteoric waters and possible mixing with surrounding recharge waters. Some shallow-buried brines exhibit relatively negative δ¹⁸O and positive δD values, reflecting the influence of regional massive carbonate sedimentation; (4) the shallow-buried brines formation experienced a complex, multi-stage hydrochemical process. The initial meteoric waters underwent evaporation and concentration, forming high-TDS brines dominated by Na⁺ and Cl⁻. Carbonate precipitation reduced Ca²⁺ and Mg²⁺ concentrations, while geothermal input contributed Li⁺, B³⁺, and Br⁻. Halite and glauberite dissolution-precipitation regulated Na⁺, Cl⁻, and SO<Stack> ₄ ²⁻ </Stack> proportions. Shallow-buried brines were genetically derived from lake brines and subsequently modified by post-burial processes including groundwater mixing and mineral reactions, developing distinctive geochemical signatures while preserving their genetic connections. This study demonstrated the distinct differences between shallow-buried brines and lake brines in salt lake systems, emphasized the roles of salt mineral dissolution and precipitation, water mixing, and burial in transforming chemical compositions of the shallow-buried brines, thereby advanced the understanding of their formation and evolution.</p>