中文摘要：

位于地幔过渡带顶面上方的低速层是近20年来固体地球物理学研究领域的一个重要发现.其对于认识俯冲作用、地幔对流模式和强度、地球内部圈层间的耦合和解耦、物质分布和迁移,乃至原始地球演化等地球深部物理化学过程有着极为重要的意义.该低速层陆续发现于全球的多个区域,所处的构造位置也不尽相同,主要包括俯冲带和大陆克拉通.其在横向上有很大的变化,主要体现在深度和厚度的波动.关于低速层的成因,虽然部分熔融成因得到了较为广泛的认同,但部分熔融作用的诱发因素、发生位置以及熔体的密度和黏度等方面的研究还不够充分.通过分析基于部分熔融成因的几个关键问题,本文最后讨论了相关的地球动力学意义.

英文摘要：

Since the discovery of the low velocity zone（LVZ）atop the mantle transition zone（MTZ）,it has been playing a significant role in the development of solid geophysics in recent 20 years. The LVZ has an enormous implication for understanding subduction behavior,patterns and intensity of mantle convection,coupled and decoupled status between adjacent layers,distribution and transportation of materials,evolution of primitive Earth and other physical and chemical processes.As a consequence,it opens a window for us to resolve scientific problems of the Earth’s interior.The LVZs detected in various regions around the world,with different tectonic backgrounds,mainly including subduction zone and continental craton,always show obvious lateral variation in depth and thickness.This paper also tries to make sense of the discovery process and summary typical characteristics of the global LVZs.With respect to the origin of the LVZ,although the partial melting model has been accepted widely,the inducing factors,location of initial partial melting and physical properties of melt like density and viscosity have not yet been sufficiently determined.Relevant geodynamic implications are also discussed eventually according to analysis of several key points based on partial melting genesis model.