Deciphering source-to-sink history from a solute perspective: A Sr isotope approach in the Qaidam Basin, NE Tibet

•Higher 87Sr/86Sr ratios of the water and minerals sourced from the Qilian Shan.•Eocene and Miocene megalakes with low solute 87Sr/86Sr ratios in the Qaidam Basin.•The two megalakes indicate hydrological connections between the basin N-S sources.•The two megalakes develop as a result of eastward migration of the basin depocenter.•Source-to-sink process of solutes and clays may be different from coarse clastics.