Solute Sources and Mechanism of Boron Enrichment in the Tataleng River on the Northern Margin of the Qaidam Basin

The Tataleng River (TTR), as an important tributary of the Da Qaidam Salt Lake (DQSL) and Xiao Qaidam Salt Lake (XQSL) in the Qaidam Basin (QB), has an exceptionally high B content. However, the solute sources and the provenance of B in the TTR are still unclear, which significantly hinders a deeper understanding of the source–sink processes of the boron deposits in the QB. In this study, water samples were collected from tributaries, mainstreams, mud volcanoes, hot springs, and rainwater in the TTR area. Through hydrochemical analysis, forward modeling, and B isotope geochemistry methods, combined with the previous research results, some findings were obtained. The hydrochemical type of TTR is Ca–Mg–Cl, and the major mechanism of controlling chemical composition is rock weathering. The solute sources in the TTR are mainly from dissolution of evaporites (75.9%), atmospheric precipitation (20.8%), and a minor contribution from carbonates (3.1%) and silicates weathering (0.6%). The higher B content (0.89–4.30 mg/L, mean = 2.13 mg/L) and lower δ¹¹B value (0.79‰–4.71‰, mean = 4.17‰) of the TTR indicate that the B sources are mainly from mixture of mud volcanic waters (56.19–199.98 mg/L, mean = 113.51 mg/L, − 1.26‰–2.22‰, mean = 0.85‰) in the upper reaches, and the deep groundwater near the Indosinian granite in the lower reaches. The significant difference in boron resources between the two lakes may be due to the enrichment of B in the late Pleistocene in the DQSL, which received exceptionally rich soluble B carried by the ancient TTR during an active tectonic period, while the weakening of tectonic activity and the diversion of the ancient TTR resulted in the supply of B with significantly reduced content to the XQSL. These results are helpful for a deeper understanding of the ore-forming mechanisms of the boron deposits in salt lake.