FORMATION MECHANISM AND TECTONIC EVOLUTION OF BACK-ARC BASINS IN THE OKHOTSK SEA

There is a number of Cenozoic back-arc basins occurred in the Okhotsk Sea as the important components of marginal basins of the western Pacific Ocean. In this paper, the tectonic architectures and the characteristics of the Okhotsk Sea are described and investigated in terms of the dynamic mechanism of basin formation and tectonic evolution. The collision of the Pacific plate and the Eurasian plate triggered the shifting of the regional pattern of compression and extension and the upwelling of the asthenosphere in deep, and brought about the multi-stage back-arc spreading of the Okhotsk Sea and the formation of the back-arc rift basins. The collision of the surrounding plates induced giant strike-slip faults, structural inversions and the reform of basins. All the factors mentioned above control the formation and evolution of the back-arc basins. The tectonic evolution of the basins can be then divided into four stages, i.e. basement amalgamation, basement folding and extensional deformation, basin rifting and depression, and tectonic inversion.