ABSTRACT

The origin of the abundant salt resources in the Gasikule salt lake in the northwest Qaidam Basin in China remains highly contested. We performed a detailed study of the hydrochemical characteristics and material sources of the Gasikule brines based on their chemical composition and hydrogen-oxygen isotopes, together with high-resolution remote sensing imagery of the stream water, surface brine, and intercrystalline brine. Stream waters within the catchment were found to be weakly alkaline and dominated by HCO₃^–, Cl^–, and Na⁺ ions. The Gasikule surface brine was also weakly alkaline and classified as chloride type. The average total dissolved solid (TDS) was 366.19 g L^–1; Cl^– and SO₄^2– were the dominant anions, and Mg²⁺ and Ca²⁺ were the dominant cations. The intercrystalline brine was weakly acidic and classified as a magnesium sulfate subtype. The average TDS was 381.80 g L^–1; Cl^– was the dominant anion, and K⁺ and Mg²⁺ were the dominant cations. The surface and intercrystalline brines were enriched in K⁺ because of the annual formation of “dry salt lake” conditions. Using Enhanced Thematic Mapper (ETM) and Satellite Probatoire Pour l’Observation de la Terre 5 (SPOT5) remote sensing data, two (approximately) north-south trends in salinity in the eastern area of the Gasikule surface brine were identified (referred to as “water swell annular anomalies”). These two anomalies were found to be located (approximately) above an existing buried fault from which Ca-Cl type deep water recharged the surface brine. Three main sources were identified for the recharge of the surface and intercrystalline brines of the Gasikule salt lake: (a) stream water sourced from rainfall and melting ice; (b) leaching of Pliocene salt-bearing host rocks that contain sulfate minerals such as gypsum, mirabilite, and celestite at the northern end of the salt lake; and (c) Ca-Cl type deep water, associated with a buried fault.