地幔柱在蒙古-贝加尔裂谷起源中的作用

The role of mantle plume on Mongolia-Baikal rift's origin

本文通过整理近年来蒙古-贝加尔裂谷有关地幔柱的研究成果,从重力异常、层析成像和接受函数等方面分析贝加尔地区上地幔的各向异性特性,并重点介绍了中蒙合作项目的深部构造研究成果,探究地幔柱在蒙古-贝加尔裂谷形成中的作用.研究发现:贝加尔裂谷区上涌物质来源于410km不连续面之下和660km不连续面之上,低速异常延伸至贝加尔裂谷下的地幔转换地带,可能是地幔柱低速异常的反映.速度异常还可能与应力环境有关,东部Pn速度低值异常与太平洋板块俯冲动力作用引起的地壳的伸展减薄和岩浆活动有关,西部Pn速度高值异常则是India板块强烈碰撞挤压动力作用所形成.蒙古-贝加尔裂谷带起源受岩石圈扩张和岩石圈不均匀性的综合影响,裂谷下的低速区存在偏转的地幔柱,偏转的地幔柱在India-Asia板块碰撞引起形变的远场力的帮助下,成为贝加尔裂谷演化和发展的主要成因之一.

This paper sorts the research findings of mantle plume in Mongolia-Baikal area, analyze upper mantle anisotropy from gravity anomaly, tomography, and receiver function and so on; make a conclusion based on the results of China-Mongolia cooperation; and study the role of Mantle plume on Mongolia-Baikal rift＇s origin. The studies show that： The upwelling material in the baikal rift zone derived from 660 km and 410 km＇s discontinuity; low-speed anomaly extends to the mantle transition zone, which could be a reaction of mantle plume. Velocity anomaly may also be related to the environmental stress; low velocity anomaly of Pn in the east was associated with the extension of the eastern region of the earth＇s crust thinning caused by the Pacific plate subduction dynamics effect; and was related to the magmatie activity; high velocity anomaly of Pn in the west is formed by the India strong collision. The origin of Mongolia-baikal rift was affect by the comprehensive influence of lithosphere inhomogeneity, the low velocity area under the rift valley exists deflection of mantle plume. The results show that mantle plume has played an important role in the formation and evolution in Mongolia- Baikal rift, and at the same time relevant to collisions with Indi-Asia also provide favorable far field.