6533b871fe1ef96bd12d2301

RESEARCH PRODUCT

Slab-triggered wet upwellings produce large volumes of melt: Insights into the destruction of the North China Craton

subject

description

Abstract Cratons have remained stable for billions of years, despite of ongoing mantle convection and plate tectonics. The North China Craton (NCC), however, is abnormal, as it has experienced a destruction event during the Mesozoic and Cenozoic which was accompanied by extensive magmatism. Several lines of evidence suggest that the (Paleo-)Pacific plate played an important role in this event. Yet, the geodynamic link between subduction and craton destruction remains poorly understood, and it is unclear why there is no systematic spatial and temporal variation of magmatism related to subduction. Here, we perform 2-D petrological-thermomechanical simulations to investigate the influence of subduction dynamics and (de)hydration processes, on craton destruction. Results show that: (1) cold slabs may transport considerable amounts of water into the mantle transition zone; (2) the subducted slab triggers wet upwellings from the transition zone that result in partial melting. Subsequently formed buoyant melt regions percolate the base of the craton, which results in a mixed magma source, deriving from the continental mantle lithosphere (CML), the asthenosphere and the oceanic crust. This is consistent with the geochemical signatures observed in 90–40 Ma rocks in the NCC; (3) cratons are more prone to be destructed by mantle convection if they are more buoyant and the subducting plate has higher water content. Our results suggest that refertilization of the cratonic mantle lithosphere by slab-triggered wet upwellings is physically a plausible mechanism of decratonization. Our model might also be applicable to the destruction of Wyoming craton in North America.