下地幔及核幔边界结构及地球动力学

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

新一代高分辨率下地幔及核幔边界的地震层析成像 ,改变了我们对全球构造模式及地球动力过程的认识。古海洋岩石圈板片一直俯冲到下地幔底部 ,其残留体在核幔边界积累 ,并支持了地幔整体对流模式。位于核幔边界上的 D″层有着十分复杂而精细的结构。紧靠核幔边界的地幔一侧发现了超低速层 ( ULVZ) ,它们可能是 D″层内的局部熔融物 ,是引起地表热点的上升地幔柱的源头。

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.