现今的地幔流动及其与板块构造的相互作用:从观测证据得到的推论  

Present-day mantle flow and its interaction with plate tectonics inferred from observational evidence

作　　者：高祥林[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地球物理学进展》2004年第3期560-567,共8页Progress in Geophysics

基　　金：国家自然科学基金项目(49834002)资助.

摘　　要：　地震波速度结构层析成像和地震各向异性分析,是推测现今地幔流动的主要观测依据.从已有研究结果看,全球尺度的地幔流动的两个主要边界驱动力是顶部的冷却和底部的加热,地幔的密度和粘度控制流动速率.沿海沟由消减板带动的地幔下沉,和沿热点下面幔柱及洋中脊的地幔上升,是地幔垂直向流动的表现.GPS等测量显示的全球板块运动在一定条件下反映地幔顶部的水平流动.地幔柱可能有不同的根源深度,沿幔柱上升的地幔流在200-350km深度转变为水平流动.消减带附近有复杂的地幔流动格局,表明局部构造条件对地幔流动的影响.大陆下一般出现两个地幔各向异性层,较深的可能反映地幔流动,并与大陆根的状态有关.在不同构造环境下,地幔流动与板块构造之间有不同形态的相互作用关系,它可能驱动板块运动,也可能对板块运动产生阻力.The current inference of mantle flow is largely based on seismic tomography and anisotropic analysis. The available results suggest that the two boundary driving forces for mantle flow on a global scale are the cooling on the top and the heating on the bottom of the mantle. The density and viscosity of the mantle control its flow rates. The mantle descending entrained by subducting slabs at trenches and the mantle rising within plumes under hotspots as well as mid-ocean ridges are the expression of vertical mantle flow. Under certain conditions, the global plate motions revealed by GPS and other measurements reflect the horizontal flow in the uppermost mantle. Mantle plumes marked by hotspots on the surface of the earth can have varied depths of origins. Rising flow within plumes can deflect by several thousand kilometers and turn to lateral flow at depths 200～350 km. Around some subduction slabs there are complicated patterns of mantle flow, indicating the influence of local tectonic settings. Below continents, two mantle seismic anisotropic layers are often observed, of which the deeper one may represent mantle flow that is associated with continental roots. In various tectonic settings, the interaction between mantle flow and plate tectonics appears in different forms, either mantle flow drives plates or producing a small drag force

关 键 词：地幔流动 板块构造 地幔柱 地震层析成像 地震各向异性 

分 类 号：P315[天文地球—地震学]