Collaborative Research: US-EAGLE (Ethiopia-Afar Grand Lithospheric Experiment): Modification of Lithospheric Structure During Continental Break- Up

0207878 Keller大陆边的构造如何形成的问题还没有得到很好的理解，因为以前的大多数工作都是在裂谷作用完成后成功地形成的裂谷边。 大陆（断层为主）和海洋（岩浆为主）裂谷端元的研究都很好，但过渡阶段是不理解的。 该项目将记录从大陆到海洋裂谷的这一关键转变。 研究所将进行地震实验，并结合地球化学、重力和结构研究，以研究埃塞俄比亚裂谷（MER）的岩石圈结构，这是一个罕见的地区，在那里可以看到从大陆裂谷到初始扩张的过渡。 在MER中，沿轴过渡到初始海底扩张提供了时间变化的空间代理。 具体目标是：1）确定横跨和沿着过渡裂谷段的详细地壳和地幔结构; 2）了解裂谷之下和裂谷之内的岩浆作用。 PI将获得地壳P和S速度横截面，可以解释为10度埃塞俄比亚裂谷的岩性。北向是活动岩浆中心首次出现的位置，沿北向是研究向完全岩浆裂谷作用过渡的方向。 他们将根据新的地震数据解释现有的和新的重力数据，并使用地球化学数据来限制上地幔的物理状态和岩浆输入地壳。该项目（美国-鹰）与已经资助的英国-鹰倡议完全结合在一起。 莱斯特、利兹和伦敦的科学家获得了联合王国的资助，于2003年1月在埃塞俄比亚裂谷上进行单一折射剖面测量，同时进行当地地震活动性研究和地震记录。 US-EAGLE PI将拍摄并记录互补的正交沿轴广角剖面;并将向这些线性阵列和当地地震网络中拍摄扇形照片，以提供3D覆盖范围。 这些地震学实验一起形成了埃塞俄比亚裂谷和地幔柱的嵌套式多尺度地震图像。 地震研究将与地球化学、岩石学和重力研究（美国）以及结构、热年代学、大地电磁和附加重力研究（英国）相结合。

0207878KellerThe architecture of continental margins in terms of how they are created is not well understood because most of the previous work has been on successfully rifted margins after rifting is complete. Both continental (fault dominated) end-members and oceanic (magma dominated) rift end-members are well studied, but the transitional stage is not understood. This project will document this critical transition from continental to oceanic rifting. The PIs will carry out seismic experiments, integrated with geochemical, gravity and structural studies, to study lithospheric structure in one of the rare areas where the transition from continental rifting to incipient spreading is captured - the main Ethiopian Rift (MER). In the MER the along-axis transition to initial seafloor spreading provides a spatial proxy for temporal variability. Specific objectives are: 1) to determine detailed crust and mantle structure across and along a transitional rift segment and 2) to understand magmagenesis beneath and within the rift. The PIs will obtain crustal P-and S-velocity cross-sections that can be interpreted for lithology across the Ethiopian rift at 10 deg. N where active magmatic centers first appear, and along-strike to the north to study the transition into fully magmatic rifting. They will interpret existing and new gravity data in light of their new seismic data, and use geochemical data to constrain the physical state of the upper mantle and magmatic inputs to the crust.The project (US - EAGLE) is fully integrated with the already funded UK - EAGLE initiative. Scientists at Leicester, Leeds and London, have been awarded UK funds to carry out a single refraction profile across the Ethiopian rift in January 2003, coupled with local seismicity studies and teleseismic recording. The US - EAGLE PIs will shoot and record a complementary orthogonal along-axis wide-angle profile; and will shoot fan shots into these linear arrays and the local seismic network to provide a measure of 3D coverage. Together, these seismological experiments form a nested, multi-scale seismic image of the Ethiopian rift and plume. The seismic studies will be coupled with geochemical and petrological and gravity studies (US), and structural, thermochronological, magnetotelluric and additional gravity studies (UK).***