CHARACTERISTICS OF MAGNETIC LINEATIONS AND RECONSTRUCTION OF SEAFLOOR SPREADING PROCESSES OF THE PHILIPPINE SEA BASIN SINCE 61 MA

The Philippine Sea Basin is the largest marginal basin in the Western Pacific. As an important part of the most spectacular trench-arc-basin system in the world, the formation and tectonic evolution of the Philippine Sea Basin can constrain the complex kinetic process of the ocean-continent transitional zone in the Western Pacific effectively. Magnetic lineations are an important evidence of seafloor spreading and their geometrical morphology can reflect the time, direction and speed of the seafloor spreading, which provide crucial information for reconstruction of the opening history of ocean basins. The magnetic anomalies in the West Philippine Basin and Shikoku Basin occur in an obvious banded pattern and the north-south zonation can be recognized in the Parece Vela Basin, although the characteristics of magnetic lineations are not distinct. Based on the analysis, comparison and interpretation of these magnetic lineations, the Philippine Sea Basin has passed seven spreading stages and a scenario of evolution from 61 Ma to present was proposed. Furthermore, the tectonic evolution and general opening processes of the marginal basins starts from rifting, and is followed by back-arc spreading with high speed, back-arc spreading with low speed, and the tectonic activities after opening.