Provenance, source weathering, and tectonics of the Yarlung Zangbo River overbank sediments in Tibetan Plateau, China, using major, trace, and rare earth elements

This paper studies the major, trace, and rare earth elements (REEs) in fluvial sediments from the Yarlung Zangbo River (YZR) on the Tibetan Plateau, China, with the aim of investigating their provenances, sediment maturity, weathering conditions, and tectonic settings. All samples and analytical techniques are based on Environmental Geochemical Monitoring Networks, which are a crucial part of IGCP259/360 (Global Geochemical Baseline). The results show that the YZR sediments consist of greywacke and litharenite with low-moderate maturities of textures and minerals. The chemical index of alteration (CIA) (49-71), plagioclase index of alteration (49-77), and index of compositional variability (ICV) values (0.82-1.54) indicate that both mature and immature sediments are present in the YZR and have experienced weak to moderate weathering with little intense weathering in the source area, which is also confirmed by the ICV-CIA, A-CN-K, A-CNK-FM, and MFW plots. Moreover, the provenance discrimination diagrams suggest that the YZR sediments are predominantly derived from felsic rocks that are close to the upper continental crust and from acid intermediates, and the tectonic settings of the YZR source rocks were associated with active continental margins and continental island arcs. The overall sediment types, weathering conditions, and tectonics of the YZR were consistent with those of the Brahmaputra River and Meghna River during the Himalayan-Tibetan orogeny, while the sediments of the Brahmaputra River are characterized by recycled-quartzose sources when compared with the other two Himalayan rivers due to the contributions of quartzolithic composition.