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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Converted waves reveal a thick and layered tectosphere beneath the Kalahari super-craton
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Converted waves reveal a thick and layered tectosphere beneath the Kalahari super-craton

机译：转换后的波揭示出卡拉哈里超克拉通下方厚厚的层状地球

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摘要

Thick and high-velocity roots are generally observed beneath the Archean cratons. Inside these high-velocity keels, velocity contrasts are detected neither by surface nor by body waves tomographies. We present here evidences based on the S-to-P and P-to-S converted waves for the existence of an irregularly stratified and thick keel beneath the Kalahari super-craton. To satisfy surface wave data and S-to-P conversions, the velocity model should have beneath the Moho a similar to 160 km thick anisotropic structure with vertical slow axis and decreasing anisotropic parameters with depth. Such a structure may stem from the preferred orientation of olivine [100] axis in the horizontal plane under shearing deformation. This structure, together with the similar to 100 kin thick layer underlying it, forms a similar to 300 km thick continental root beneath the cratons. Inside this root, the P and S velocities should be higher on average respectively by an amount of 6% and 4% than the AK 135 velocity model. Beneath similar to 300-350 km depth, a low velocity zone is clearly detected that may be either the remainder of large magma reservoirs related to cratonic flood basalts or a melted silicate layer created by the transformation, just above the 410-km deep discontinuity, of wadsleyite assembly to olivine assembly. (c) 2007 Elsevier B.V. All rights reserved.
机译：通常在太古代克拉通下方观察到厚而高速的根。在这些高速龙骨内部，无论是通过表面层析还是体波层析成像都无法检测到速度对比。我们在此基于S-to-P和P-to-S转换波提供的证据表明，卡拉哈里超克拉通下方存在不规则分层且厚实的龙骨。为了满足表面波数据和从S到P的转换，速度模型在莫霍面以下应具有类似于160 km厚的各向异性结构，该结构具有垂直慢轴，且各向异性参数随深度减小。这种结构可能源于剪切变形下水平面中橄榄石[100]轴的首选方向。该结构及其下约100 kin厚的层一起在克拉通下形成了约300 km厚的大陆根。在该根内部，P和S速度应分别平均比AK 135速度模型高6％和4％。在类似于300-350 km的深度之下，清楚地检测到一个低速带，可能是与克拉通洪水玄武岩有关的大型岩浆储集层的剩余部分，也可能是该转变产生的熔融硅酸盐层，位于410 km深的不连续点上方，瓦兹利岩组装到橄榄石组装。 （c）2007 Elsevier B.V.保留所有权利。

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