STRUCTURE OF LOWER MANTLE AND CORE-MANTLE BOUNDARY REGION AND ITS GEODYNAMICS

The new generation of high resolution seismic tomographic images of lower mantle and core mantle boundary region have provided amazing insights for global tectonics and the dynamic processes of the Earth. The ancient oceanic lithospheric slabs sank into the bottom of the lower mantle, and the material of remnants slabs accumulated at the core mantle boundary. The model of convective flow of the whole mantle was supported by the new seismic images. The D discontinuity above the core mantle boundary has a fine and complicated structure and interpreted as a chemical or phase transition zone, and add the possibility that the cold thermal anomaly associated ancient slabs leads to the velocity anomaly. One of the most exciting discovery is the ultralow velocity zone (ULVZ) which close the core mantle boundary in lower mantle side, it may be the partial molten layer and the sources of the upwelling plume which cause the hot spots at the Earth's surface.