The development of rifting and magmatism in the multiply rifted Turkana Depression, East Africa: Evidence from surface-wave analysis of crustal and uppermost mantle structure
The development of rifting and magmatism in the multiply rifted Turkana Depression, East Africa: Evidence from surface-wave analysis of crustal and uppermost mantle structure
复制标题
东非图尔卡纳凹陷多重裂谷中裂谷和岩浆活动的发展：来自地壳和上地幔结构表面波分析的证据
DOI：
10.1016/j.epsl.2023.118386
复制
发表时间：
2023
影响因子：
5.3
通讯作者：
Kounoudis R
中科院分区：
文献类型：
--
作者：
Kounoudis R
图尔卡纳洼地将埃塞俄比亚高原和东非高原分开。在中生代，这里是一个东北-西南向裂谷（安扎裂谷）失败的地方，但现在在北部的埃塞俄比亚主裂谷和南部的东部裂谷之间的交界处，有东西向的努比亚-索马里分离。然而，这些裂谷阶段对地壳和岩石圈地幔结构和热结构的时间积分效应知之甚少。利用图尔卡纳凹陷和北方坦桑尼亚南部新地震台网的数据，我们制作了该地区详细的各向异性地壳和上地幔剪切波速度模型。在坦桑尼亚东部，与邻近地区相比，上地幔波速（4.4-4.5 km/s）略低，且与裂谷平行的地壳各向异性一致，这意味着尼扬扎裂谷发育于两个难处理太古代地块之间相对较弱的移动的岩石圈带。在图尔卡纳凹陷的上地壳（100公里）深处，最慢的速度（13.2公里/秒）归因于厚中生代沉积盆地。凹陷内没有任何地方的中下地壳或岩石圈地幔与波速一样慢，或地震各向异性一样强，如在熔体丰富的中部和北方主要埃塞俄比亚裂谷（MER）和埃塞俄比亚高原更北。高上地幔波速（1.45公里/秒），与扩大MER裂谷到埃塞俄比亚南部，证实存在难熔的元古代岩石圈作为一个流变边界裂谷的发展。与中生代安扎裂谷作用失败相关的地壳变薄区域也位于快速波速（>4.5 km/s）的地幔岩石圈之下，这意味着该地区抵抗了中新世-近代伸展作用和岩浆作用的重大热机械改造。因此，先前存在的地壳薄带并不一定代表板块薄弱区，在那里将发展随后的裂谷阶段。
The Turkana Depression separates the uplifted Ethiopian and East African Plateaus. It was the site, in Mesozoic times, of a failed episode of NE–SW-oriented rifting (the Anza Rift), but now hosts E–W-oriented Nubia–Somalia separation at the junction between the Main Ethiopian Rift in the north and the Eastern Rift to the south. However, the time-integrated effect of these rifting phases on crustal and lithospheric mantle architecture and thermal structure is poorly understood. Utilising data from new seismograph networks in the Turkana Depression and northern Tanzania Craton, we produce a detailed anisotropic crustal and uppermost mantle shear-wave velocity model of the region. Within the Tanzania Craton, slightly lower uppermost mantle wavespeeds (4.4–4.5 km/s) compared to neighbouring regions, and coincident rift-parallel crustal anisotropy, imply the Nyanza Rift developed in relatively weak mobile belt lithosphere between two refractory Archean blocks. At upper-crustal (≲10 km) depths in the Turkana Depression, the slowest velocities (≲3.2 km/s) are attributed to thick Mesozoic-age sedimentary basins. Nowhere within the Depression is the mid-to-lower crust or lithospheric mantle associated with wavespeeds as slow, or seismic anisotropy as strong, as that observed below the melt-rich central and northern Main Ethiopian Rift (MER) and Ethiopian Plateau further north. High upper mantle wavespeeds (≳4.5 km/s), coinciding with the broadening of MER-rifting into southern Ethiopia, confirm the presence of refractory Proterozoic lithosphere acting as a rheological boundary to rift development. Thinned crustal zones associated with failed Mesozoic Anza rifting are also underlain by fast wavespeed (>4.5 km/s) mantle lithosphere, implying this area has resisted significant thermomechanical modification from Miocene-Recent extension and magmatism. Pre-existing crustal thin zones do not, therefore, necessarily represent zones of plate-weakness where subsequent phases of rifting will develop.
登录
查看更多内容
DOI：
10.1007/bf00251068
发表时间：
1994-12
期刊：
Geologische Rundschau
影响因子：
--
作者：
C. Ebinger;A. Ibrahim
通讯作者：
C. Ebinger;A. Ibrahim
影响因子：
2.9
作者：
D. Hendrie;N. Kusznir;C. Morley;C. Ebinger
通讯作者：
D. Hendrie;N. Kusznir;C. Morley;C. Ebinger
影响因子：
3.7
作者：
Thomas A. J. Merry;I. Bastow;R. Kounoudis;C. Ogden;R. Bell;L. Jones
通讯作者：
Thomas A. J. Merry;I. Bastow;R. Kounoudis;C. Ogden;R. Bell;L. Jones
环境噪声断层扫描显示埃塞俄比亚主裂谷的地壳 S 波速度结构
影响因子：
2.8
作者：
Seongryong Kim;A. Nyblade;J. Rhie;C. Baag;T. Kang
通讯作者：
T. Kang
影响因子：
3.5
作者：
Emry, E. L.;Shen, Y.;Bao, X.
通讯作者：
Bao, X.