Late Triassic continental eclogite in the central Tibetan Plateau reveals 2500-km-long Paleo-Tethys continental subduction

Permian−Triassic eclogites exposed on the Tibetan Plateau have traditionally been attributed to Paleo-Tethys oceanic subduction. Here we report new data that indicate a continental-subduction origin of the Pianshishan eclogites along the Longmuco-Shuanghu Paleo-Tethys suture in northern Tibet. Phase equilibrium modeling and zircon U-Pb dating constrain eclogite-facies metamorphism of ∼2.1 GPa/530 °C to have occurred ca. 235 Ma. Xenocrysts of ca. 1850 Ma metamorphic zircons and crustal trace element signatures reveal a continental protolith for the Pianshishan eclogites, demonstrating deep subduction of continental passive margins during the early Late Triassic. The Qianmai eclogites along the Changning-Menglian suture in Southwest China have the same petrogenesis, indicating that these two coeval eclogites resulted from continental subduction that extended over 2500 km along the Paleo-Tethys suture. This collision not only marks the end of the Paleo-Tethys Wilson cycle but also could have formed a high-elevation range, comparable in length to the Himalaya, that amplified Tethyan megamonsoons during the Late Triassic Carnian Pluvial Episode.