Rift Focussing and Magmatism During Late-Stage Rifting in Afar, Ethiopia
Rift Focussing and Magmatism During Late-Stage Rifting in Afar, Ethiopia
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埃塞俄比亚阿法尔晚期裂谷期间的裂谷聚焦和岩浆作用
DOI：
10.1002/essoar.10503895.1
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Moore C
中科院分区：
文献类型：
--
作者：
Moore C
促进大陆裂谷和海底扩张之间过渡的过程仍然不清楚。通过阿法尔延伸到红海的空间分布的变化表明了裂谷的时间演变。我们开发了一个时间序列的哨兵-1干涉合成孔径雷达（干涉合成孔径雷达）的地面形变观测覆盖整个阿法尔裂谷从2014年至2019年，以研究在所有岩浆段的扩展分布。通过将GNSS观测，我们解决了在垂直，裂谷垂直，裂谷平行方向的三维平均速度。结果显示了裂谷上长期板块运动的空间分布，以及各个火山中心的变形，包括Dallol，Nabro和Erta 'Ale。我们发现，在北方和中部阿法尔，大部分的扩展容纳在+/- 15-30公里的岩浆扩散中心。在阿法尔南部，靠近努比亚-阿拉伯-索马里三联点，延伸分布在90-180 km，这可能表明随着裂谷成熟，裂谷集中度增加。我们还观察到Dabbahu-Manda-Hararo段的快速表面隆起和裂谷垂直延伸，速度分别为33 +/- 4 mm/年和37 +/- 4 mm/年。这高于18-20毫米/年的背景扩展率，但自2006-10年以来已下降了55- 70%。这些数据表明，这是由于持续的长期响应2005-10裂谷幕，与潜在的持续过程低于部分，包括低地壳粘性反应和岩浆运动。对地表变形的持续长期观测为阿法尔的构造-岩浆过程提供了关键制约因素。
Processes that facilitate the transition between continental rifting and sea-floor spreading remain unclear. Variations in the spatial distribution of extension through Afar and into the Red Sea are indicative of temporal evolution of the rift. We develop a time series of Sentinel-1 interferometric synthetic aperture radar (InSAR) observations of ground deformation covering the whole Afar Rift from 2014-2019, to study the distribution of extension across all magmatic segments. By incorporating GNSS observations, we resolve 3D average velocities in the vertical, rift-perpendicular, and rift-parallel directions. Results show the spatial distribution of long-term plate motions over the rift, as well as deformation at individual volcanic centres, including Dallol, Nabro, and Erta ’Ale. We find that in northern and central Afar, the majority of extension is accommodated within +/- 15-30 km of magmatic spreading centres. In southern Afar, near the Nubia-Arabia-Somalia triple-junction, extension is distributed over 90-180 km, which may indicate an increase in rift focussing with rift maturity. We also observe rapid surface uplift and rift-perpendicular extension at the Dabbahu-Manda-Hararo segment with velocities of 33 +/- 4 mm/yr and 37 +/- 4 mm/yr respectively. These are higher than the background extension rate of 18-20 mm/yr, but have decreased by 55-70 % since 2006-10. The data suggests that this is due to an on-going long-lived response to the 2005-10 rifting episode, with potential continued processes below the segment including a lower-crustal viscous response and magma movement. Continued long-term observations of surface deformation provide key constraints on tectono-magmatic processes in Afar.