Bulldoze and rebuild: Modifying cratonic lithosphere via removal and replacement induced by continental subduction

Abstract

Establishing the mechanisms for craton modification is critical for understanding cratonic stability and architecture. It is well known that oceanic subduction and mantle plumes can destroy and destabilize the overriding cratonic lithosphere, but the role of continental subduction in craton modification remains unclear. In the North China craton (NCC), which experienced deep continental subduction of the Yangtze block (YB) during the early Mesozoic, we report the presence of the YB crust embedded in the overriding craton. Combining our new results with previous observations, we argue that during 250–220 Ma, a 200-km-long tract of the NCC lithosphere was bulldozed by the subducted YB, resulting in a lithospheric suture far from the suture zone at the surface. This lithospheric removal occurred at middle-lower crustal levels (16–20 km depth)—much shallower than previously thought possible. The bulldozed NCC lithosphere was replenished by the subducted YB continental lithosphere rather than the asthenosphere, thus terminating the lithosphere modification. With essentially no net loss of lithosphere during deep continental subduction, the NCC maintained its stability until Early Cretaceous paleo-Pacific oceanic subduction. This “bulldoze and rebuild” model can thus account for how a craton maintains stability during a collision with another continental plate.