Continental rifting in the South China Sea through extension and high heat flow: An extended history

Abstract

We present a new extensional tectonic model for the Cenozoic history of SE Asia and the opening of the South China Sea (SCS), proposing a feedback mechanism by which intracontinental rifts initiate and propagate without invoking mantle plumes.Four principal tectonic models have been proposed for SCS opening: 1) Slab pull from subduction of a Proto South China Sea (PSCS); 2) Extrusion tectonics from the India-Asia collision; 3) Basal drag from a mantle plume; and 4) Backarc rifting. Each model was developed around different particular data, and all tend to perpetuate independently through selective data prioritisation. We present a new GPlates model, showing that the geological and geophysical correlations between the opposing SCS conjugate margins best agrees with a common initial development on the South China Margin, and that regional development via protracted extension since the Mesozoic is in agreement with available paleomagnetic data for Borneo.The geodynamic mechanism for protracted lithospheric extension in SE Asia is via the development of progressive feedback processes, initiated by Mesozoic slab rollback and migration of the subduction zone beneath South China, leading to intracontinental thinning and extension. This in turn drove passive asthenospheric upwelling, increasing heat flow and crustal ductility, and enhancing further extension as a wide rift rather than narrow crustal neck. Subsequently, following sufficient continental extension, SCS oceanic spreading occurred. This feedback mechanism (involving shallow, not deep mantle processes) may enhance and enable intracontinental rifting elsewhere.