东非大裂谷的地壳和上地幔密度结构  

The 3-D density structure of the great East-Africa Rift from the asthenosphere to crust

作　　者：钱知之 杨文采 QIAN Zhizhi;YANG Wencai(Zhejiang University,Hangzhou,310058)

机构地区：[1]浙江大学,杭州310058

出　　处：《地质论评》2024年第1期1-8,共8页Geological Review

基　　金：中国科学院学部咨询评议项目(编号:2022-ZW11-A-0024)的成果。

摘　　要：利用卫星重力场数据和小波多尺度分析方法对东非大裂谷进行三维密度结构成像,取得了东非大裂谷地壳和上地幔多个深度等效层上的密度扰动图像,为东非大裂谷岩石圈结构和动力学的研究提供了重要佐证。结果表明,东非大裂谷中段的西支裂谷与东支裂谷的幔源熔体同源,但是西支裂谷发育较不充分、形成较晚。东非大裂谷的动力学模式为熔流体上涌的树形分叉模式,其要点包括:(1)低密度流体在软流圈大面积上涌;(2)流体在岩石圈继续上涌,部分转化为基性岩浆岩,平面面积缩小;(3)进入地壳后上涌熔流体分叉成多支,平面总面积进一步缩小;(4)熔流体上涌到上地壳后仅在裂谷带活动,反映为火山链和玄武岩带。Satellite gravity field data and wavelet multi-scale analysis methods were used to image the threedimensional density structure of the Africa Great Rift,and the density disturbance images on multiple depthequivalent layers of the crust and upper mantle of the Valley were obtained,which provided important supporting evidence for the study of the lithospheric structure and Earth dynamics.The results show that the western rift branch of the middle section of the East African Rift Valley is homologous to the mantle-source melt of the eastern rift valley,but the western branch is not fully developed with later formed time.The kinetic mode of the Great Rift Valley is a tree-shaped bifurcation mode of melt-and-fluid upwelling,which includes:①low-density fluid swells up in a large area of the asthenosphere;②the melt-and-fluid continues to surge up in the lithosphere,partially converted into basic magma,and the plane area shrinks;③after entering the earth's crust,the upwelling molten fluid bifurcates into multiple branches,and the total plane area is further reduced;④the melt—fluid only moves in the rift zone after the upsurge to the upper crust,reflecting the volcanic chain and basalt belt.

关 键 词：东非大裂谷 卫星重力场 小波多尺度分析 三维密度结构成像 熔流体运动 

分 类 号：P542[天文地球—构造地质学]