Tectono - Magmatic and stratigraphic evolution of final rifting and breakup: Evidence from the tip of the southwestern propagator in the south China sea

Abstract

In this study, we explore the tectono-sedimentary and magma evolution of final rifting and continental breakup along the SW conjugate margins of the South China Sea (SCS). Based on new seismic observations, we define and map three rift domains, referred to as “box-shaped”, “wedging” and “proto-oceanic”. Each of these domains is characterized by: (1) the shape and thickness of the crust; (2) the specific architecture of the syn-rift mega-sequence that includes three system tracts each one including syn- and post-rift packages; and (3) different deformation styles.Results are synthetized in two Wheeler diagrams that provide a complete description of the tectono-magmatic and stratigraphic evolution of final rifting and breakup within two neighboring segments of the SW-SCS. We conclude that: 1) localization of deformation occurs simultaneous and perpendicular to the migration of magma-emplacement in front of a propagating spreading system, 2) the arrival of magma controls continental breakup, and 3) the final rifting stage and breakup are diachronous. The relationships between extension, sedimentation and magmatic processes observed in the SW-SCS differ significantly from the classical models derived from the N-Atlantic or the Alpine Tethys. Main differences include the way the crust is thinning/necking, the sharp transition to breakup and the style of magma emplacement linked to crustal breakup.