Subduction of the Western Pacific Plate underneath Northeast China: Implications of numerical studies

The geodynamic process of the deep subduction of the western Pacific Plate underneath Northeast China is critical for understanding the extensional events and volcanism in Northeast China. Understanding of this process depends on: (1) the initial time of the subduction, (2) the trench retreat velocity during the subduction process, (3) the contribution of Indian-Eurasian collision and Pacific-Eurasian subduction to extensional events in the northeast of China. However, information on these three issues is very limited. We use several regional models to gain insight into these three issues. Each of the models includes temperature-dependent viscosity structures, and distinct velocity patterns at the surface. Our results show that the subduction of the Pacific Plate under the Eurasian plate started most probably around 70 Ma. To be consistent with the tomography under Northeast China, trench retreat must be included in the models, with a rate less than 45 km/Ma that has been estimated in the past. We suggest that the extension events in the northeast China are attributed to Indian-Eurasian collision and Pacific-Eurasian subduction according to the velocity evolution in our models.