Cenozoic Reconstruction of Magmatism and Basin Development Within the South China Sea and Their Implications to Regional Tectonic Evolution

Abstract

The South China Sea (SCS) is one of the most active exploration regions for oil and gas over the past decades. It is curtail to understand the evolution of basin development and the tectonic framework if one wish for successful exploration of this region. This marginal sea situated within three major tectonic plates of the Eurasian, Indo-Australian and Philippine plate that exhibited various types of plate boundaries (divergent, convergent and transcurrent) and complex tectonic evolutions due to subsequent subduction and convergences of numerous micro blocks and accretionary prisms during the Cenozoic time. In order to decipher the evolution and their tectonic framework, correlation between the temporal and geographical distribution of Cenozoic magmatism, and the development histories of major basins within and surrounding the SCS were conducted. Four major tectonic episodes can be recognized. (1) The SE ward younging trend of A type granite and high-K calc-alkaline magmatic rock in SE Asia during Paleogen indicated the initiation of continent extension by eastward retreating of subduction of the Pacific plate to Asia. This also induced episodic rifting within the basins along the Asia continental shelf NW of SCS marked by rift onset unconformities (Tg). (2) The SCS begin to spread in N-S direction from the NE region along the E-W trending ridge (C11–7) around 34–33 Ma possibly response to southward slab pull during the subduction of proto-South China Sea oceanic crust, which is also marked by the beak up unconformity (T7) within surrounding basins. (3) The left lateral shearing activity of the Red River Shear zone (27∼16 Ma) due to collision of India into Eurasia trigger a southward ridge jump event (C6b∼5c) and the development of the SW sub-region of SCS. The clockwise rotation of Indochina accompanying the left-lateral shearing event induced asymmetric graben and half graben development within the basins west of the SCS. (4) The SCS seized spreading around 15.5 Ma as the Pacific sea plate continued subducted westward. However, this compressional setting reinforced the subsidence of basins to the maximum depth till Pliocene

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014