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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.
The low velocity layer located above the top of the mantle transition zone is an important discovery in the field of solid geophysics over the past 20 years and is of great importance for the understanding of subduction, mantle convection mode and intensity, coupling and decoupling between inner earthosphere, And migration, as well as the deep earth physicochemical processes such as the original evolution of the earth, etc. The low-velocity layer has been successively discovered in many regions of the world and located in different structural positions, including the subduction zone and the continental craton. It has a great change in the horizontal direction, mainly reflected in the depth and thickness of the fluctuations.For the low-speed formation of the cause, although the cause of partial melting has been more widely recognized, but the partial melting of the trigger factor, the location and the melt Density, viscosity and other aspects of the research is not enough.Through the analysis of several key problems based on the cause of partial melting, the paper finally discusses the relevant geodynamic significance.