First Identification of Late Permian Nb‐Enriched Basalts in Ailaoshan Region (SW Yunnan, China): Contribution From Emeishan Plume to Subduction of Eastern Paleotethys

Abstract

Abstract Interactions between ocean plate subduction and the nearby mantle plume represent a possible major drive for mantle heterogeneity. We first report Late Permian (~261 Ma) Nb‐enriched basalts (NEBs) in the Ailaoshan region. The Ailaoshan NEBs are characterized by high Nb (10.1–11.5 ppm) and Nb/La (1.2–1.3), positive Nb‐Ta anomalies and ε Nd( t ) (+5.65 to +6.21), and low and mantle‐like zircon δ 18 O (5.28–5.75‰). Our results demonstrate that the source region contains an enriched mantle component, which may have derived from the nearby Emeishan plume. The Ailaoshan NEBs were possibly generated by mixing of subduction‐derived, mid‐ocean ridge basalt (MORB)‐like components and mantle plume‐derived, enriched components. We suggest that the Late Permian rollback of the Ailaoshan oceanic slab may have entrained the Emeishan plume material into the subduction zone, which caused compositional heterogeneity in the mantle wedge and formed the Ailaoshan NEBs.