Cyclical continental extension reworks and destructs the cratonic lithosphere of South China

Continents with cratonic cores can resist deformation, and thus survive billions of years in the geological record. Tectono-thermal reworking is a key process in continental evolution because it alters composition and structure of some continents, weakens, and finally destructs or even dismembers them. Typical examples of reworked continents develop in subduction or collision settings, mostly situating in East Asia, Western North America, or the Tethyan collisional zones. 

In western Pacific, East Asian continental margins suffered extensive continental reworking and lost part of their continental lithosphere and developed a wide (>1000 km) extensional province. Across the South China Block, Mesozoic cyclical tectonics destructed a large portion of its cratonic lithosphere. Such strongly modified continent represents an ideal target to reveal the process and mechanism of continental reworking.

We analyzed and synthesized the structural evolution of extensional domes and illustrated the process of lithospheric thinning of Mesozoic South China before Cenozoic rifting of the large marginal seas. Structural and geochronology data of the extensional domes in the SCB indicate Cretaceous two-stage extension, a weaker extension during the early extension, and a faster and stronger extension in the later extension. Unlike the previous rapid, one-cycle delamination model occurred in the North China Craton, the destruction process of South China operates in a cyclical, progressive manner in which compression destabilized the edge of the cratonic lithosphere and the following extension destructs the unstable part to thin the lithosphere. This process, as an endmember of lithospheric destruction mechanisms, requires cyclical tectonics of the subduction zone and the overriding plate, which has been widely reported in the Cordilleras of the eastern Pacific margin. The progressive lithosphere destruction model may also explain how ancient cratons shrink by subduction-related tectonics.