Late Permian Bimodal Volcanic Rocks in the Northern Qiangtang Terrane, Central Tibet: Evidence for Interaction Between the Emeishan Plume and the Paleo‐Tethyan Subduction System

Abstract

AbstractMany studies provide compelling evidence for a fossil mantle plume beneath the Late Permian Emeishan large igneous province located near the southeastern margin of the central Tibetan Plateau, a region associated with the Paleo‐Tethyan subduction system. However, little is known about whether direct plume‐subduction interaction occurred during the Late Permian. Here we report geochronological, mineralogical, geochemical, and Sr‐Nd‐Hf‐O isotopic data for the Late Permian (~259–256 Ma) bimodal volcanic rocks (BVRs) in the northern Qiangtang Terrane (NQT), central Tibet. These BVRs consist mainly of basalts, rhyolites, and rhyolitic tuffs. The rhyolites with A‐type affinity were generated by partial melting of newly underplated basalts. Geochemical and isotopic data suggest that two components (ocean island basalt‐type mantle and subducted sediment‐derived fluid) were involved in the generation of the basalts in an extensional back‐arc region. Considering the Permian tectonic evolution of the NQT, we propose that this enriched ocean island basalt‐type mantle was distinct from the Paleo‐Tethyan depleted upper mantle. It most likely originated from Emeishan‐plume material that flowed westward from the South China Block to the nearby NQT, driven by slab rollback‐induced counterflow. The presence of high‐temperature A‐type rhyolites in bimodal back‐arc magmatism also indicates a special subduction setting influenced by a nearby plume. Thus, we propose that the Late Permian BVRs were the result of interaction between the Emeishan plume and the Paleo‐Tethyan subduction system.