Imaging Lithospheric Discontinuities Beneath the Northern East African Rift Using S-to-P Receiver Functions.
Imaging Lithospheric Discontinuities Beneath the Northern East African Rift Using S-to-P Receiver Functions.
复制标题
使用 S-to-P 接收器函数对东非北部裂谷下方的岩石圈不连续性进行成像。
DOI：
10.1029/2018gc007463
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Lavayssière A
中科院分区：
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作者：
Lavayssière A
岩石圈成像是理解裂陷过程中伸展机制的关键。大陆裂陷导致岩石圈的机械拉伸和减薄、减压上涌、加热、有时软流圈的部分熔融以及地幔岩石圈的潜在部分熔融的组合。北方东非裂谷系是研究这些过程的理想场所，因为它暴露了从构造活动大陆裂谷向初始海底扩张的过渡。在这里，我们使用S-to-Preceiver函数来成像东非裂谷系统最北端下方的岩石圈结构，在那里它形成了埃塞俄比亚主裂谷，红海裂谷和亚丁湾裂谷之间的三重连接。我们拍摄了埃塞俄比亚高原下31 ± 6公里处的莫霍面。埃塞俄比亚主裂谷下的地壳厚度为28 ± 3 km，而在阿法尔北方则减薄至23 ± 2 km。我们确定了一个负相，即在埃塞俄比亚高原下67 ± 3 km深度处速度随深度减小，可能与岩石圈-软流圈边界（LAB）有关，并且在裂谷下方缺乏LAB相。使用观察和波形建模，我们表明，平台下的LAB相可能是由少量的部分熔融定义的。缺乏一个实验室阶段下的裂缝表明熔体渗透通过最北端的东非裂谷系统下面的岩石圈的基础。
Imaging the lithosphere is key to understand mechanisms of extension as rifting progresses. Continental rifting results in a combination of mechanical stretching and thinning of the lithosphere, decompression upwelling, heating, sometimes partial melting of the asthenosphere, and potentially partial melting of the mantle lithosphere. The northern East African Rift system is an ideal locale to study these processes as it exposes the transition from tectonically active continental rifting to incipient seafloor spreading. Here we useS‐to‐Preceiver functions to image the lithospheric structure beneath the northernmost East African Rift system where it forms a triple junction between the Main Ethiopian rift, the Red Sea rift, and the Gulf of Aden rift. We image the Moho at 31 ± 6 km beneath the Ethiopian plateau. The crust is 28 ± 3 km thick beneath the Main Ethiopian rift and thins to 23 ± 2 km in northern Afar. We identify a negative phase, a velocity decrease with depth, at 67 ± 3 km depth beneath the Ethiopian plateau, likely associated with the lithosphere‐asthenosphere boundary (LAB), and a lack of a LAB phase beneath the rift. Using observations and waveform modeling, we show that the LAB phase beneath the plateau is likely defined by a small amount of partial melt. The lack of a LAB phase beneath the rift suggests melt percolation through the base of the lithosphere beneath the northernmost East African Rift system.