Geochemical characteristics and provenance of aeolian sediments in the Yarlung Tsangpo valley, Southern Tibetan Plateau

Aeolian sediments and other surface deposits are widespread along the broad valleys across the Yarlung Tsangpo (YT) catchment on the southern Tibetan Plateau (TP) and are considered important sources of global dust. However, geochemical differentiation in different reaches, sedimentary circulation, and dust transmission processes in the YT valleys are poorly understood. In this study, 47 samples of different types of sediments were collected from different YT valleys, and the major and trace-element (excluding rare-earth elements, REEs) compositions of 42 bulk samples and the trace elements (including REEs) compositions for the fine (< 75 mu m) fractions of 21 samples were determined. The results show that the different sediments are predominantly sourced from local felsic bedrocks, originating mainly from the Lhasa terrane through the tributary systems, which are primarily controlled by the physical weathering, and only incipient chemical weathering. The geochemical characteristics of the various sediment types exhibited spatial differentiation because of the complex structure and topography, intense surface circulation, and mixing processes of the detritus from both banks. Owing to the complexity of regional surface processes, conventional non-isotopic geochemical methods might not be the most effective tool for sediment provenance tracing on a large spatial scale. Nevertheless, aeolian deposits in the broad valleys across YT mainly have a near-source clastic supply of local origins, belonging to a regional self-cycling process, which might not be transported by wind across different reaches because of high topographic obstacles.

Automated summary

The study reveals that sediments in the Yarlung Tsangpo valleys are mainly sourced from local felsic bedrocks, primarily controlled by physical weathering. The geochemical characteristics of different sediment types vary due to complex structure and topography, intense surface circulation, and mixing processes.