Identification of High δ18O Adakite‐Like Granites in SE Tibet: Implication for Diapiric Relamination of Subducted Sediments

Abstract

AbstractSediment relamination in subduction zones is posited to be important for the compositional evolution, physical structure and material recycling of the Earth. Despite support from numerical experimental modeling and geophysical observation, magmatic evidence for relamination is rare and difficult to identify in ancient and modern convergent systems. Here we report newly identified ca.32–27 Ma adakite‐like granites with high δ18O values (up to 10.38‰) from the Ailaoshan‐Red River (ASRR) shear zone in western Yunnan (SE Tibet). Their geochronological and compositional data strongly exhibits significant contributions from Permian‐Eocene sedimentary rocks in the lower crust (30–45 km). Our study provides further evidence that the lower crust may be partially composed of more felsic lithologies likely originating from rapid supracrustal material recycling via diapiric relamination of (meta)sedimentary material during Cenozoic‐age continental subduction. The ASRR adakite‐like granites thus represent clear magmatic evidence for sediment relamination in a subduction system.