The Invasion of Remote Groundwater into Deserts on the Alxa Plateau: Acid Soluble Sr Isotopic Evidence

87Sr/86Sr ratios and Ca2+, Sr2+ concentrations of acid soluble fractions of surface sands are measured for four deserts (Taklimakan, Badain Jaran, Tengger and Mu Us) with similar mineral and geochemical compositions in the W-E direction over North China. Ca2+ and Sr2+ concentrations have an excellent correlation, are the highest in the Taklimakan Desert with the low rainfall, decreasing Eastwards, and the lowest in the Mu Us sandy land with the high rainfall. The rainfall is the main factor controlling cationic concentration. Acid soluble 87Sr/86Sr ratios have regional characteristics different from cationic change in the four deserts. Acid soluble 87Sr/86Sr ratios are lower than 0.71 for the Taklimakan desert, more than 0.7112 for the Badain Jaran and Tengger deserts, and change between 0.71 and 0.7112 in the Mu Us sandy land. Acid soluble 87Sr/86Sr ratios of surface sands in the Taklimakan desert and the Mu Us sandy land are only affected by climate factors. The Badain Jaran and Tengger deserts were affected not only by climate factors but also by additional factors, e.g. remote groundwater. By calculation, the effects of remote groundwater presents 47% on the Badain Jaran desert, 44% on the Tengger desert, respectively, approaching the impact of climate factors.