Crust and Upper Mantle of the South China Sea (probabilistic-deterministic gravity model)

Abstract

Rheological layering of a tectonosphere of the South China Sea (SCS) on the crust rigid (the depth interval of 5–30 km), viscous subcrustal (the depth interval of 30–70 km), rigid lower lithospheric (50–90 km), astenospheric (80–150 km) and rigid subastenospheric (the depth interval is more than 150 km) is established. Distributions of the density inhomogeneities connecting with the main tectonic events in SCS are caused by the Paleo-Pacific’s convergence, and later — the Philippine’a oceanic plate with the Philippine archipelago and further — with the Asian margin. In this zone by distributions of density contrast in a tectonosphere are tracing Cenozoic processes of a subduction, stretching, transformic shift and structure of the central type of the probable plume nature which form an evolutionary sequence: back arc, or paleo-oceanic spreading → the Philippine subduction → NE-stretching with shift → formation of the structure of the central type of a probable plume origin. The structures caused by convergence of the Asian continent with the Indo-Australian plate are isolated from the West Pacific margin, and the underthrsting of rigid lithospheric plates from the South under a lithosphere of the margin sea reflects traces of more ancient collision of fragments of the Gondwana with Asian continent.