From freshwater inflows to salt lakes and salt deposits in the Qaidam Basin, W China

Abstract The Qaidam basin in W China is an immense hyperarid intramontane with flat vast playas and salt lakes on the Qinghai-Tibet Plateau. central about 2800–2900 m a.s.l. elevation enclosed by mountain ranges reaching > 5800 Qilian Mountains 6200 eastern Kunlun Mountains. extensive of are covered gypsum or halite very subordinate additional solids. In this contribution we report chemical composition inflows to (analysis 30 water samples collected summer 2008 2009) together 22 samples. Salt small ponds formed at topographic depressions. Some cover 300 km 2 surface but shallow (1–2 deep). Most NaCl dominated contain typically 250–300 g kg −1 total dissolved solids (TDS). industrially used produce KCl fertilizer, LiCl, boron strongly modified deep produced oil fields. Lakes along borders high mountains not fully saturated halite. However, also these lost most Ca drastically enriched Mg some B Li. development natural follows a path producing Ca-deficient that ultimately precipitate Mg-bearing carbonates chlorites addition upon evaporation. form continuous drastic evaporation waters supplied basin. All carry considerable amounts Cl characterized Cl/Br ratios. These characteristics suggest load originates mostly from re-dissolved windblown deposited sand up altitudes bordering ranges. Also, thermal ascending faults chloride. Their low ratio however suggests Na derived minerals basement rocks fluid-rock interaction T 130 °C. fluids boron, indicating co-precipitated borax derives (tourmaline). Consequently, presented data improve understanding how brines lake develop wide range chemically distinct low-TDS sequences precipitated formed.