Sedimentary geochemistry of the Weihe River sediments, Central China: implications for provenance and weathering

Modern river sediments sampled from the Weihe River, Central China, were analyzed in regard to facies, grain size, major and trace element, and rare earth element (REE). The main aim of the study was to investigate source rock provenance and paleoweathering intensity. Grain-size and outcrop analyses indicate that sediments from the Weihe River are predominantly slit (< 62 μm) and sand (62 μm to 2000 μm). Major and trace element concentrations show inverse correlations with SiO2 content and grain size. Silty sediments are enriched in REE relative to upper continental crust (UCC), whereas sandy sediments tend to be depleted. UCC-normalized REE distribution fingerprints indicate that the silt sediments are mainly derived from the Loess Plateau, while sandy sediments are mainly sourced from the Qinling Mountains. Discrimination functions and La/Th ratio and Hf abundance discrimination diagram also show that silty sediments are mainly derived from quartzose sediments, the main components of Loess Plateau, while sandy sediments are mainly derived from felsic igneous source, the main components of Qinling Mountains in the region where tributaries flow. The chemical index of alteration (CIA), plagioclase index of alteration(PIA), and chemical index of weathering (CIW) suggest that Weihe River sediments are immature and have experienced relatively minor chemical weathering. This work has an important bearing on the general understanding of the role that source rock characteristics and weathering regime have on the formation of clastic sediments in modern rivers and provides a critical baseline for which future work on the Weihe River sediments can be evaluated against. © 2021, Saudi Society for Geosciences.