WHAT FLAT-SLAB SUBDUCTIONS CAN DO: AN EXAMPLE FROM MESOZOIC SOUTH CHINA

We document here the development of a Permian-Jurassic orogen in South China that migrated ca. 1300 km from the coastal region into the continental interior. We use a flat-slab subduction model to explain the development of such a broad intra-continental orogen and a puzzling chain of events that followed the sweeping orogeny: (1) the coupling between the flat-slab and the overlying continental lithosphere caused the cratonward migration of the orogen with a magmatic gap above the flat-slab; (2) downward pulling of the subducted flat-slab at the rear of the migrating orogen, due to eclogite facies metamorphism, led to the formation of a shallow-marine basin at the wake of the orogen; (3) the eventual delamination and foundering of the flat-slab from its centre led to widespread anorogenic magmatism, lithospheric rebound and extension; (4) coastward retreat of a regenerated steep subduction system explains the coastward migration of the Jurassic-Cretaceous magmatic belt that has mixed extensional and arc signatures. The South China example may serve as a classic case for the multiple effects of flat-slab subduction including migrating orogenesis and foreland flexure, syn-orogenic sagging behind the orogen, post-delamination lithospheric rebound, and the development of a Basin-and-Range style broad magmatic province.