Abstract: Abstract: ObjectiveLithium resources in shallow brines of the Qaidam Basin are undergoing continuous depletion, shifting strategic focus to Tertiary deep brines enriched with elements including potassium (K), lithium (Li), boron (B), strontium (Sr), bromine (Br), and iodine (I) as critical alternative targets. Based on comprehensive evaluations of resource endowment, infrastructure, and industrial capacity, the Yahu Structural Zone in the central Qaidam Basin has emerged as the sole area where deep brine resources have undergone extensive exploration and development. Nevertheless, the genetic evolution of these deep brines and the specific mechanisms responsible for lithium enrichment remain poorly understood. MethodsThis study leverages data from five newly drilled deep boreholes penetrating Neogene strata within the Yahu Structural Zone. By analyzing the lithological architecture of the brine reservoir, hydrochemical characteristics of brines from distinct aquifers, and hydrochemical monitoring data acquired during production tests, and integrating these with a comparative analysis of deep brines from other structural zones in the western Qaidam Basin, we investigate the origin, evolution, and provenance of soluble lithium in the Yahu deep brines. ResultsOur results indicate that the deep brines in the Yahu area, similar to those in the western Qaidam Basin, were primarily derived from paleo-formation waters preserved during early sedimentation. The evolutionary pathway of these brines has been collectively governed by their initial hydrochemical character and a series of water-rock interactions during burial diagenesis. Furthermore, strong genetic correlations between lithium, potassium, and rubidium in the deep brines suggest an enrichment process linked to water-rock reactions between deeply buried pore fluids and silicate-dominated sedimentary sequences. ConclusionsThe Yahu Structural Zone exhibits effective geological confinement and a large-scale closed system. Production tests confirm a substantial brine resource with stable hydraulic characteristics, underscoring the area's superior metallogenic conditions and promising potential for further exploration.