## 1 Introduction  
The South China Sea (SCS) is a Late Cretaceous to Early Miocene marginal sea, which mainly experienced rifting, breaking up, and seafloor spreading under a stretching mechanism during its formation [1, 2]. Rifting and seafloor spreading, as two continuous phases of passive continental margin evolution, have recorded different styles of passive margins tectonics in the SCS [3, 4, 5]. The northern margin of the SCS is similar to the general continental margin. The lithosphere thinned and extruded toward the ocean, and the basin development and tectonic deformation have also deformed and migrated from the land to the ocean [6]. In the process of seafloor spreading, the proto-South China Sea (PSCS) subduction and the collision between the southern margin and Kalimantan Island have changed the tectonics of the SCS southern margin. This event changed the extension pattern of the conjugate margin from symmetric to asymmetric [7; 8]. The mechanism and structure of the conjugated margin of the east sub-basin (ESB) have revealed a rapid conversion from rift to ocean expansion. A few models have been developed to explain the formation of the oceanic crust and basins in the SCS. In early studies, the SCS was considered a back-arc basin formed by the back-arc action of the Philippine Sea plate [9; 10]. Further research contradicts this view since the back-arc drifting was propelled by the gradual extension of the Philippine Sea plate, and no subduction system was associated with the SCS [11; 12; 13]. Then, the paleo-Pacific subduction rollback model was proposed. It is believed that the back-arc stretching was triggered by the Pacific plate subduction [14; 15]. The ESB of the SCS was opened in a near N-S direction, and the spreading direction of the SWSB was a NW-SE trend. However, the Pacific plate has been subducted in the NWW direction since the Middle Eocene. The spreading ridge of the SCS is nearly vertical to the Pacific island arc, and the stress patterns do not match [11; 16]. Based on the tectonic evolution history of the SCS basin, there are two main widely accepted models: the collision-subduction model [12; 17; 18] and the collision-extrusion (escape) model [19; 20]. The collision-subduction model suggests that the crustal subduction under North Kalimantan Island and the Pacific Ocean plate resulted in the westward opening of the PSCS. In the Late Cretaceous-Moocene period, the PSCS subducted under the Pacific plate and Kalimantan Island and formed an open ocean basin [21; 22]. The collision-extrusion (escape) concept implies that the Indian plate moved northward since the Paleocene and collided with the Eurasian plate, which has triggered the strike-slip shear of the main fault zones to support the extrusion movement [12; 23; 24; 25]. Based on the collision-subduction model, a bidirectional subduction model of the PSCS was established. It suggests that the southern PSCS began to undergo subduction southward in the Early Eocene, and the northern PSCS subducted northward at 30-20 Ma. Seismic tomography also revealed two near-horizontal tabular tomography anomalies under the PSCS and North Kalimantan Island [25; 26]. In addition to the above models, the mantle plume model is also considered a possible tectonic model to promote the rupture of the SCS [18; 27]. The mantle plume model considers that mantle plume upwelling partially influenced intraplate volcanism in the PSCS spreading and basaltic magmatism at oceanic ridges in the SCS spreading [12; 24]. Despite numerous studies of marginal seas and rift basins in the Cenozoic, many unanswered questions remain in the SCS, such as the nature of the rift-to-rupture transition and the extensional patterns of its margins [28; 29]. How the South China Sea Basin achieved the rapid transition from tension fracture-rupture-seafloor spreading remains inconclusive. Although many models have been proposed for the opening and evolution of the South China Sea Basin, systematic collation studies have also been conducted [30].