Delamination‐Induced Upwelling and Its Implications for Late Mesozoic Magmatism in the Songliao Basin, NE China

Abstract Lithospheric thinning in the Songliao Basin is often attributed to late Mesozoic Izanagi Plate subduction in the eastern part of the Central Asian Orogenic Belt. However, delamination of the continental lithosphere may be a more likely mechanism to explain the consequent mantle circulation and the distinct geological morphology and magmatic processes of the Songliao Basin. By incorporating experimental constrained eclogitization and melting conditions at high temperature and pressure conditions into 2‐D petrological‐thermomechanical numerical models, we systematically model an intracontinental delamination process. The numerical experiments show that delaminated segments force hot asthenospheric mantle upwards, causing characteristic magmatic expression in the overriding continental lithosphere. Dehydration of the mantle transition zone (MTZ) would rehydrate a layer of the asthenospheric mantle and form a channel for deep mantle upwelling. The material produced by the interaction between the partial melting of the delaminated segments and deep mantle peridotite would be brought up with the hot mantle upwelling, generating igneous rocks in the intracontinental crust. The crustal magmatism from delamination is expressed in two stages: (a) a rapid phase of high‐volume magmatism related to the detachment of lower lithosphere and replacement with asthenosphere; and (b) a slower and extended phase of magmatism associated with partial melting of the foundered lithosphere in the MTZ. The model provides a novel explanation for the regional intracontinental magmatism that is characterized by a short‐term volcanic climax and a subsequent longer‐term weakened magmatism in the Songliao Basin since the late Mesozoic.