Kinematic Constraints on Mantle-Lithosphere Interactions in Eastern Africa

东非地幔-岩石圈相互作用的运动学约束大陆岩石圈的裂谷作用是控制大陆生长演化和洋盆诞生的基本过程。它通过控制裂谷盆地及其成功裂谷的对应物被动大陆边缘的油气和热资源的形成而起着至关重要的经济作用。大陆裂谷作用通过热传导和岩浆作用，并可能通过地幔流动对岩石圈变形的力学作用，涉及整个地幔-岩石圈系统。因此，大陆裂谷是研究地球较深和较浅部分之间耦合和交换的主要背景。东非大裂谷（East African Rift，简称ERF）是现今地球上唯一一个将大陆完全分裂的裂谷，它被认为是裂谷和大陆分裂的现代原型，为这类研究提供了一个主要的背景。东非大裂谷（East African Rift，简称ERF）的稀疏GPS和地震跳跃矢量数据，加上最近岩石圈下结构的层析成像图像和地震各向异性数据，表明地幔流，与坦桑尼亚克拉通200 km厚的岩石圈龙骨相互作用，驱动了非洲东部岩石圈运动和大陆裂谷。这一假设正在通过以下方式得到检验：（1）利用全球定位系统在坦桑尼亚新的和现有的地点进行的测量，确定地幔柱的运动学;（2）根据全球定位系统速度和地震各向异性数据的反演以及地幔柱-岩石圈相互作用模型，评估软流层流动，（3）将模拟和"估计“的流动作为软流层三维有限元模型的边界条件，这项工作是解决大陆板块构造的一些基本问题：伸展应变广泛分布或最初局限于狭窄的地带？地幔流场和板块龙骨之间的相互作用是否影响大陆板块内部应变的定位和方向？除了这些全球性的构造问题，我们的工作将回答以下问题，具体到东非：什么是岩浆贫乏的西部裂谷系统的起源？东西裂谷系之间联系的运动学是什么？

Kinematic constraints on mantle-lithosphere interactions in East AfricaRifting of continental lithosphere is a fundamental process that controls the growth and evolution of continents and the birth of ocean basins. It plays a crucial economical role by controlling the formation of hydrocarbon and thermal resources in rift basins and their successfully rifted counterparts, passive continental margins. Continental rifting involves the entire mantle-lithosphere system through heat transfer and magmatism, and possibly through the mechanical effect of mantle flow on lithospheric deformation. Continental rifts are therefore a prime setting for the study of coupling and exchanges between the deeper and shallower parts of our planet. The East African Rift (EAR), commonly cited as a modern archetype for rifting and continental breakup and the only rift on Earth that is currently splitting a continent over its entire length, provides a prime setting to such studies.Sparse GPS and earthquake skip vector data in the East African Rift (EAR), coupled with recent tomographic images of sub-lithospheric structures and seismic anisotropy data, suggest that mantle flow, possibly associated with the African Superplume, interacts with the 200~km-thick lithospheric keel of the Tanzanian craton, driving lithospheric motions and continental rifting in eastern Africa. This hypothesis is being tested by (1) establishing the kinematics of the EAR using GPS measurements at new and existing sites in Tanzania, (2) assessing asthenospheric flow from an inversion of GPS velocities and seismic anisotropy data and from plume-lithosphere interactions models, (3) using the modeled and ``estimated'' flow as boundary conditions to a 3D finite element model of asthenosphere-lithosphere interactions.This work is addressing some of the fundamental questions of continental plate tectonics: Are extensional strains broadly distributed or initially localized to narrow zones? Do interactions between mantle flow fields and cratonic keels influence the localization and orientation of strain within continental plates? In addition to these global tectonic issues, our work will answer the following questions specific to East Africa: What is the origin of the magma-poor Western rift system? What is the kinematics of linkage between the Western and Eastern rift systems?