Lithium and strontium isotopic systematics in the Nalenggele River catchment of Qaidam basin, China: Quantifying contributions to lithium brines and deciphering lithium behavior in hydrological processes

•The dissolved Li in NRB is mainly supplied by hydrothermal fluid and surface water.•Only 3–5% of the hydrothermal fluid provided over 85% of dissolved Li to salt lakes.•The dynamic behavior of dissolved Li is distinct in various hydrological regions.•Remote recharge pattern of hydrothermal fluids leads to a high Mg/Li ratio in brines.