Geochemistry of fine sediment from small catchments reveals silicate weathering intensity and spatial variation across the Tibetan Plateau

Abstract

Silicate weathering on the Tibetan Plateau holds profound implications for long-term carbon cycle. The spatial variability in climate and topography on the plateau poses challenges in investigating silicate weathering processes, fluxes, and intensities. Here, we present a new data set on the major and trace element compositions of fine sediments collected from small catchments across the Tibetan Plateau. Trace elements reveal sediment recycling, though this has only a marginal influence on the chemical index of alteration (CIA). The provenance of sediments is characterized by intermediate and felsic rocks. There is an increasing trend of weathering intensity from north to south across the Tibetan Plateau. In the plateau’s interior, silicate weathering intensity is mainly controlled by climatic factors. For instance, to the north of the Tanggula, precipitation is pivotal in governing weathering intensity, while in regions to the south of the Tanggula and in the Yarlung Zangbo suture zone, temperature emerges as the dominant control. Intriguingly, the river water chemistry and sediment geochemistry reveal different temporal scales of silicate weathering intensity. Short-term weathering intensity is mainly influenced by precipitation and freeze–thaw cycles, and long-term weathering intensity is controlled by temperature. In contrast, relief exerts a strong impact on silicate weathering intensity in the southeastern margin of the Tibetan Plateau. This study provides a geochemical framework for evaluating silicate weathering intensity at the catchment scale and highlights a climate-controlled weathering intensity in the interior of the Tibetan Plateau.