Isotopic characteristics of river sediments on the Tibetan Plateau

Abstract

We systematically collected 40 modern clastic sediment samples from rivers in different tectonic units of the Tibetan Plateau and measured their Sr–Nd isotopic compositions. The isotopic characteristics provide insight into the controversial paleo-tectonic affinity of terranes of the Tibetan Plateau and the provenance of Songpan–Ganzi flysch complex. The Qilian Terrane and Himalaya Terrane have more negative ε Nd(0) values (from − 14.3 to − 11.8 and from − 20.64 to − 13.26, respectively) and high 87Sr/ 86Sr values (from 0.719674 to 0.738818 and from 0.721020 to 0.824959, respectively), reflecting old and mature continental crust origin of these two terranes. The southern Lhasa Terrane is more radiogenic in ε Nd(0) values (from − 8.82 to − 3.8) and low in 87Sr/ 86Sr values (from 0.711504 to 0.719489), implying the combined impact of the Neo-Tethys mantle and Himalaya old continental crust. Sr–Nd isotopic compositions of the Qilian Terrane are similar to those in the Yangtze Craton, indicating that the Qilian Terrane was probably separated from the Yangtze Craton. Sr–Nd isotopic characteristics of the Songpan–Ganzi Terrane are similar to the Yangtze Craton and are remarkably different to those in the North China Craton, eastern Kunlun–Qaidam and the central Qiangtang metamorphic belt, implying that the widely distributed flysch complex of the Songpan–Ganzi Terrane was sourced from the Yangtze Craton.