The Model of Formation of the Western Pacific Marginal Seas: Vortex Geodynamics, Seismicity, and Mantle Upwelling

An extended and improved model of the origin and evolution of marginal seas in the strike-slip megazone due to the lateral interaction of the Eurasian and Pacific lithospheric plates is proposed. In the megazone, fragmentation of continental and oceanic plates, mantle upwelling, and ascending and descending lithospheric seismic vortexes occur. As a proof of the validity of the proposed model, the paper presents data from factor analysis, results of gravity and termophysical modeling, an analysis of distributions of earthquake magnitudes in 3D space, and geochemical features of volcanism in the Sea of Japan and Sea of Okhotsk. Study of the variability of earthquake magnitudes for the Sea of Okhotsk region revealed traces of vortex processes in the circular orientation in the variability vectors of magnitudes in the subcrustal viscous layer and in the asthenosphere. The head of the mantle plume has a typical mushroom shape, and its central trunk extends into the mantle below a depth of 200 km. Studies of the isotopic age and geochemical features of volcanic rocks in the Sea of Okhotsk and Sea of Japan have allowed researchers to identify the magma sources-lithospheric, asthenospheric, and subasthenospheric (plume); to trace the geochronological sequence in the ascent of mantle substrate; and to determine the underlying formation mechanisms for the marine basins. The origin of marginal seas is discussed and compared to other geodynamic models with different geotectonic paradigms. The origin of marginal seas is discussed and compared with other geodynamic models of different geotectonic paradigms.