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The crustal structure of the southern Davie Ridge offshore northern Mozambique – A wide-angle seismic and potential field study
Tectonophysics ( IF 2.9 ) Pub Date : 2020-03-01 , DOI: 10.1016/j.tecto.2020.228370
Maren Vormann , Dieter Franke , Wilfried Jokat

Abstract Some of the oldest surviving oceanic basins in the world, the Mozambique and West Somali basins, were created during the breakup of Gondwana, starting around 180 Ma. Between the two basins, relative movements of West Gondwana and East Gondwana, including Madagascar, created a shear zone, the Davie Fracture Zone (DFZ) with a topographic elevation (Davie Ridge - DR) marking its centre. The crustal composition of the DFZ and DR is a subject of speculation and debate. In this study, we present seismic refraction data across the prominent topography of the southern DR. Ray tracing of the wide-angle data as well as additional seismic amplitude modelling and 2.5D density modelling constrain its crustal structure and architecture. The data indicate that in the Mozambique Channel the DR consists of fragments of continental crust with a thickness of 10 to 12 km. An oceanic crust indenter extends northward from the Mozambique Basin into the area between the DR and the East African margin at 16.5°S. Northeast of the DR, at 41.8°W/14.5°S, the Somali Basin is probably floored by 6 km thick oceanic crust. Hence, the continental DR separates oceanic crust of the Somali and Mozambique basins. The transitional crustal area at the central Mozambican margin is underlain by high velocity lower crust (HVLC). The HVLC has velocities up to 7.3 km/s and extents along the margin, vanishing northward between 16.5° and 14.5°S. At the Madagascan side of the DR, at 16.5°S, the highly intruded stretched continental crust is 9 km thick and possibly underlain with a smaller HVLC of 2.9 km thickness and an E-W extent of 120 km. The oceanic crust at 14.5°S represents the oldest part the Somali Basin, which formed after the initial NW-SE rifting between East and West Gondwana.

中文翻译:

莫桑比克北部近海戴维岭南部地壳结构——广角地震和潜在场研究

摘要 世界上一些现存最古老的海洋盆地,莫桑比克和西索马里盆地,是在冈瓦纳大陆分裂期间形成的,大约从 180 Ma 开始。在两个盆地之间,西冈瓦纳和东冈瓦纳(包括马达加斯加)的相对运动形成了一个剪切带,戴维断裂带 (DFZ) 以地形高程 (戴维岭 - DR) 为中心。DFZ 和 DR 的地壳组成是一个推测和争论的主题。在这项研究中,我们展示了 DR 南部突出地形的地震折射数据。广角数据的射线追踪以及附加的地震振幅建模和 2.5D 密度建模限制了其地壳结构和构造。数据表明,在莫桑比克海峡,DR 由厚度为 10 至 12 公里的大陆地壳碎片组成。一个洋壳压痕从莫桑比克盆地向北延伸到 DR 和东非边缘之间的区域,位于 16.5°S。在 DR 的东北部,在 41.8°W/14.5°S,索马里盆地可能被 6 公里厚的洋壳所覆盖。因此,大陆 DR 将索马里和莫桑比克盆地的洋壳分开。莫桑比克中部边缘的过渡地壳区下方是高速下地壳(HVLC)。HVLC 的速度高达 7.3 km/s,沿边缘延伸,在 16.5° 和 14.5°S 之间向北消失。在 DR 的马达加斯加一侧,在 16.5°S,高度侵入的拉伸大陆地壳厚 9 公里,可能下伏有较小的 HVLC 2。9 公里的厚度和 120 公里的 EW 范围。位于 14.5°S 的洋壳代表了索马里盆地最古老的部分,它是在东西冈瓦纳大陆之间最初的 NW-SE 裂谷之后形成的。
更新日期:2020-03-01
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