Early Permian mantle plume-subduction zone interaction across the >2000-km-wide Paleo-Tethys Ocean

The presence of ocean-island basalt (OIB)-type magmas in convergent margins implies complex mantle geodynamic processes. This study reports an Early Permian (ca. 282 Ma) association of OIB-type and Nb-enriched arc-type rocks from the Northern Qiangtang Terrane, Tibet. Both suites share predominantly depleted Nd-Hf isotopic compositions, suggesting derivation from an asthenospheric mantle containing enriched components. The Nb-enriched arc-type rocks additionally record slab interaction. Spatial distribution with OIB-type rocks located proximal and arc-type rocks distal to the trench supports a sub-slab origin for the enriched component. After a systematic evaluation of various potential geodynamic models, we interpret this origin as reflecting slab tearing in the vicinity of the trench. Spatiotemporal, geochemical, and thermal comparisons suggest that this mantle source may be linked to the 290–285 Ma Qiangtang-Panjal large igneous province, which was located >2000 km to the south. This linkage implies long-distance transport of plume material across the Paleo-Tethys Ocean and subsequent plume-subduction zone interaction beneath the Northern Qiangtang margin. We propose that slab tearing facilitated the upwelling and melting of this previously enriched material, providing the setting for long-distance plume material transport and plume-subduction interaction in ancient convergent systems. The transport of plume material was likely driven by large-scale northward mantle flow. This large-scale mantle-flow framework may also provide a qualitative working hypothesis for linking plume-related thermal weakening and basal traction to the initial rifting and northward drift of the Cimmerian microcontinents.