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首页> 外文期刊>Geochemistry, geophysics, geosystems >Structure of the mantle beneath the Alboran Basin from magnetotelluric soundings
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Structure of the mantle beneath the Alboran Basin from magnetotelluric soundings

机译：从大地电磁测深看Alboran盆地下的地幔结构

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We present results of marine MT acquisition in the Alboran sea that also incorporates previously acquired land MT from southern Spain into our analysis. The marine data show complex MT response functions with strong distortion due to seafloor topography and the coastline, but inclusion of high resolution topography and bathymetry and a seismically defined sediment unit into a 3-D inversion model has allowed us to image the structure in the underlying mantle. The resulting resistivity model is broadly consistent with a geodynamic scenario that includes subduction of an eastward trending plate beneath Gibraltar, which plunges nearly vertically beneath the Alboran. Our model contains three primary features of interest: a resistive body beneath the central Alboran, which extends to a depth of approximate to 150 km. At this depth, the mantle resistivity decreases to values of approximate to 100 Ohm-m, slightly higher than those seen in typical asthenosphere at the same depth. This transition suggests a change in slab properties with depth, perhaps reflecting a change in the nature of the seafloor subducted in the past. Two conductive features in our model suggest the presence of fluids released by the subducting slab or a small amount of partial melt in the upper mantle (or both). Of these, the one in the center of the Alboran basin, in the uppermost-mantle (20-30 km depth) beneath Neogene volcanics and west of the termination of the Nekkor Fault, is consistent with geochemical models, which infer highly thinned lithosphere and shallow melting in order to explain the petrology of seafloor volcanics.
机译：我们介绍了Alboran海中海洋MT采集的结果，并将先前从西班牙南部采集的陆地MT纳入了我们的分析。海洋数据显示，复杂的MT响应函数由于海底地形和海岸线而具有严重的变形，但是将高分辨率地形和测深法以及地震定义的沉积物单元包含到3-D反演模型中已经使我们能够对下层的结构成像地幔。所得的电阻率模型与地球动力学情景基本一致，该地质动力学情景包括俯冲直布罗陀下方的一个东向趋势板块，该板块几乎垂直地在Alboran下方俯冲。我们的模型包含感兴趣的三个主要特征：Alboran中央下方的电阻体，延伸到大约150 km的深度。在这个深度，地幔电阻率降低到大约100 Ohm-m的值，略高于在相同深度的典型软流圈中看到的值。这种转变暗示着平板性质随深度的变化，也许反映了过去俯冲的海底性质的变化。我们模型中的两个导电特征表明，俯冲板释放出的流体或上地幔中有少量的部分熔体（或两者都有）。其中一个位于阿尔伯兰盆地中心，在新近纪火山岩之下的最上地幔（20-30公里深处）和内科断层末端以西的那一个，与地球化学模型是一致的，该模型推断出岩石圈和岩石的高度变薄。浅融化以解释海底火山岩的岩石学。

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