Using mineralogy and Sr-Nd isotopes of gypsum to constrain the provenance of sediments in the western Qaidam Basin, northern Tibetan Plateau: implications for neo-tectonic activities

The extremely thick sedimentary sequence in the Qaidam Basin, northeastern Tibetan Plateau (TP) is closely related to the uplift of the TP. Due to the scarcity of minerals that can be dated continuously, little is known about the isotopic responses of the minerals in this area to the changes in the weathering and sources over a long time period. A 938.5-m long core (magnetostratigraphic age of ∼ 2.8–0.1 Ma) was drilled in the western Qaidam Basin in 2008. The mineralogy and isotopic compositions of gypsum in this core were investigated. The gypsum recorded the primary information about the brine that formed during ∼ 2.8–0.1 Ma. The variations in the Sr isotopes (0.709817–0.714473, average of 0.711249) and Nd (0.512114–0.512614, average of 0.512184) of the gypsum samples suggest that the weathering products of the rocks in the Kunlun and Altyn mountains (Mts) likely exerted a strong control on the Sr-Nd isotopes of the lakes. The climate and the Sr content/isotopic compositions of the gypsum samples were affected by the regional tectonic activities throughout the evolution of the paleolake since 2.8 Ma. The results of this study demonstrate that Sr-Nd isotopes are useful tools for investigating the origins of evaporite deposits and the interactions between tectonic activities and climate change.