Petrology of Lancang (Upper Mekong) River Sand

The texture and composition of river sediments are key to understanding the characteristics of source rocks, chemical weathering in the source area, physical modifications during transport, and human impacts within watersheds. This study analyzes 47 very fine to coarse size sands from the Lancang (Upper Mekong) River in China to monitor compositional variations and assesses the contribution of different geological units to trunk-river sediments. Lancang River sands are mostly feldspatho-quartzo-lithic in composition, with quartz content increasing downstream at the expense of lithic fragments (especially of carbonate lithics). Sand is mostly generated from the Lincang and Baoshan blocks, with subordinate contributions from the Simao and Changdu blocks. This study provides new insights into erosional and depositional processes in the Lancang River and emphasizes the impact of human activities on river sediment transport.