Yangtze River sediments from source to sink traced with clay mineralogy

River bed sediments were collected from the main stream and major tributaries of the Yangtze River for clay mineralogy study. Surface sediments from the Yarlung Zangbo River on the Tibetan Plateau were also examined for comparison. The results show that the clay mineral compositions of the Yangtze River display a similar pattern through the whole truck stream, with illite being dominant, kaolinite and chlorite being lesser abundant, and smectite being minor component. Clay mineralogy shows distinct differences in the tributaries, which correspond to the heterogeneous source rocks and weathering intensity of the drainage. The illite crystallity and the illite chemical weathering index (5 Å/10 Å peak ratio) both increase downstream, indicating a increasing trend of hydrolysis along the river. It also indicates that the upperstream of the drainage is characterized with physical weathering while the middle- and lower reaches are controlled by chemical weathering process. In accordance with the result derived by the illite indexes, sediment input from upperstream including Yalong Jiang, Dadu He, Min Jiang and Jialing Jiang accounts for the major sediment load, whereas Wu Jiang, Xiang Jiang, Gan Jiang and Dongting Lake provide relatively less sediments.

► We study the clay mineral of the whole Yangtze River and its tributaries. ► The main stream display a similar pattern while the tributaries is different. ► The upstream is physical weathering but mid-downstream are chemical weathering. ► Tributaries in the upstream supplies more to the main stream. ► Rivers draining the Tibetan Plateau are controlled by local rocks and tectonics.