Inverse models of gravity data from the Red Sea–Aden–East African rifts triple junction zone
Inverse models of gravity data from the Red Sea–Aden–East African rifts triple junction zone
复制标题
红海-亚丁-东非裂谷三重交界区重力数据的反演模型
DOI：
10.1111/j.1365-246x.2005.02736.x
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发表时间：
2005
影响因子：
2.8
通讯作者：
B. Oluma
中科院分区：
文献类型：
--
作者：
C. Tiberi;C. Ebinger;V. Ballu;G. Stuart;B. Oluma
伸展和岩浆作用的共同作用永久性地改变了大陆裂谷和火山被动边缘的地壳结构。红海-亚丁湾-埃塞俄比亚裂谷三重接合带提供了一个独特的机会来研究软流圈上升流上方或附近的早期火山边缘形成。我们使用重力反演和正演模拟来研究渐新世洪水玄武岩省的地壳和上地幔结构的横向变化，该地区随后被扩展成红海、亚丁湾和埃塞俄比亚主裂谷。我们用新的和现有的地壳厚度地震估计来约束和检验得到的模型。特别是，我们预测了凸起的高原和裂谷的地壳厚度，并用最近的接收函数分析校准了我们的结果。我们讨论了这些结果，并从岩浆边缘构造的角度讨论了密度对比的三维分布。主要结论是：(1)阿法尔坳陷三联结带地壳密度较大（+240 kg m−3）和/或较薄（23 km）；(2)沿埃塞俄比亚主裂谷轴存在较浅的莫霍线，地壳厚度从南部的32 ~ 33 km下降到阿法尔坳陷南部的24 km；(3)在广泛隆起的渐新世洪水玄武岩省下存在较厚的地壳（~ 40 km），表明地壳底沉积补偿了大部分高原隆起；(4)在几个崩塌的火山口复群下，在~ 8°N， 39°W处观察到可能存在岩浆底沉积或裂谷结构的分割。这些结果表明岩浆活动深刻地改变了整个洪水玄武岩省的地壳结构。
SUMMARY The combined effects of stretching and magmatism permanently modify crustal structure in continental rifts and volcanic passive margins. The Red Sea‐Gulf of Aden‐Ethiopian rift triple junction zone provides a unique opportunity to examine incipient volcanic margin formation above or near an asthenospheric upwelling. We use gravity inversions and forward modelling to examine lateral variations in crust and upper mantle structure across the Oligocene flood basalt province, which has subsequently been extended to form the Red Sea, Gulf of Aden and Main Ethiopian rifts. We constrain and test the obtained models with new and existing seismic estimates of crustal thickness. In particular, we predict crustal thickness across the uplifted plateaux and rift valleys, and calibrate our results with recent receiver function analyses. We discuss the results together with a 3-D distribution of density contrasts in terms of magmatic margin structure. The main conclusions are: (1) a denser (+240 kg m −3 ) and/or a thinner crust (23 km) in the triple junction zone of the Afar depression; (2) a shallower Moho is found along the Main Ethiopian rift axis, with crustal thickness values decreasing from 32‐33 km in the south to 24 km beneath the southern Afar depression; (3) thicker crust (∼40 km) is present beneath the broad uplifted Oligocene flood basalt province, suggesting that crustal underplating compensates most of the plateau uplift and (4) possible magmatic underplating or a segmentation in the rift structure is observed at ∼8 ◦ N, 39 ◦ W beneath several collapsed caldera complexes. These results indicate that magmatism has profoundly changed crustal structure throughout the flood basalt province.