浅地幔系统的动力学作用  

On dynamic processes of the shallow-mantle system

作　　者：杨文采[1] YANG Wencai(School of Geosciences,Zhejiang University,Hangzhou,310027)

机构地区：[1]浙江大学地球科学学院,杭州310027

出　　处：《地质论评》2020年第3期521-532,共12页Geological Review

基　　金：国家自然科学基金资助项目(编号:41574111)的成果。

摘　　要：近年来地幔地球物理三维成像为地下深部构造和物质运动提供了大量数据和信息,促进了人们对浅地幔系统物质运动的特征和动力学作用的认知。按照运动的方向不同,浅地幔系统的物质运动可分为三种主要形式:水平运动、向上涌动和向下沉动。浅地幔系统物质向下运动由地球引力势能引起,其他方向的运动主要由热能和动能引起。除了动力来源之外,浅地幔系统物质运动的方向还取决于岩石圈和软流圈的物质属性,因为高黏度介质阻挡物质运动,而低黏度介质加速物质运动。软流圈物质的水平蠕动差异,产生了岩石圈的伸展、拆离和推覆等复杂构造,速度和动能较大软流圈物质的蠕动,一定会带动岩石圈板块物质的运动和变形。软流圈物质的向上涌动又可以进一步细分为上涌运动、上拱运动和穿刺运动三种方式,它们对上方岩石圈的作用效果是不同的。浅地幔系统的物质下沉运动有多种形式,包括俯冲、拆沉和交代作用,也经常伴随有软流圈物质上涌,在微观上是一种对偶运动。这种对偶运动造成了克拉通地壳的底垫和岩石圈的陆根。软流圈大规模的物质运动,包括大洋中脊物质上涌、大陆碰撞造山和大洋俯冲的前陆拉张,在全球地震层析成像图上都有清晰的反映。中国东南沿海一带是浅地幔系统物质运动的一个特殊地区,可能是由于白垩纪伊佐奈崎板块俯冲,激发东亚大陆边缘软流圈上涌,然后又造成大陆边缘岩石圈局部拆沉等一连串动力学作用叠加形成的。In recent years,the geophysical 3D imaging of the mantle has provided a great deal of data and information of deep structures and of the underground material motion,promoting the cognition of the characteristics and dynamics of the shallow mantle system.According to the direction of motion,the material movement in the shallow mantle system can be divided into three main forms:horizontal motion,upwelling and sinking motions.The energy that causes the downward movement of matter in the shallow mantle system is caused by the potential energy generated by the earth's gravity,and the motion in other directions is mainly caused by deep heat and kinetic energy.In addition to the power sources,the direction of the material motion of the shallow mantle system also depends on the material properties of the lithosphere and the asthenosphere,as the high viscosity rocks resist the movement of the material and the low viscosity medium accelerates the movement of the material.The horizontal creep difference of asthenosphere mass produces complex structures such as stretching,underplating and nappe in the lithosphere,and the creeping of asthenosphere material with greater velocity and kinetic energy will certainly drive the movement and deformation of the lithosphere plates.The uprising of the asthenosphere can be further subdivided into three ways,the upsurge motion,the upper welling movement and the diapir motion,which have different effects on the upper lithosphere.The material sinking movement of the shallow mantle system takes many forms,including subduction,delamination and metasomatosis,and is often accompanied with the upwelling of the asthenosphere.These mass movements causes the delamination of the craton crust and the land roots of the lithosphere.Large-scale material movements in the asthenosphere,including upwelling of matter in the mid-ocean ridge,collisions of continents,and pre-land pull-ups of ocean subduction,are clearly reflected in the global seismic tomography maps.The southeast coast of China is a special a

关 键 词：大陆动力学 浅地幔系统 三维地球物理图像 水平运动 向上涌动 

分 类 号：P541[天文地球—构造地质学]