Neoproterozoic low to negative δ18O volcanic and intrusive rocks in the Qinling Mountains and their geological significance

► Striking 18O depleting occurs in the Yaolinghe volcanic and associated intrusive rocks. ► The 18O depleting was the result of meteoric fluid-in hydrothermal alteration. ► SIMS zircon U-Pb dating yields 635-790 Ma ages for the Yaolinghe volcanic rocks. ► SIMS zircon U-Pb dating gives 714-721 Ma ages for the intrusive rocks. ► The hydrothermal alteration started earlier than 790 Ma, continued to at least 714 Ma and stopped before 635 Ma.