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首页> 外文期刊>Nature >Reconciling surface plate motions with rapid three-dimensional mantle flow around a slab edge
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Reconciling surface plate motions with rapid three-dimensional mantle flow around a slab edge

机译：通过围绕板边缘的快速三维地幔流来协调表面板的运动

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摘要

The direction of tectonic plate motion at the Earth's surface and the flow field of the mantle inferred from seismic anisotropy are well correlated globally, suggesting large-scale coupling between the mantle and the surface plates. The fit is typically poor at subduction zones, however, where regional observations of seismic anisotropy suggest that the direction of mantle flow is not parallel to and may be several times faster than plate motions. Here we present three-dimensional numerical models of buoyancy-driven deformation with realistic slab geometry for the Alaska subduction-transform system and use them to determine the origin of this regional decoupling of flow. We find that near a subduction zone edge, mantle flow velocities can have magnitudes of more than ten times the surface plate motions, whereas surface plate velocities are consistent with plate motions and the complex mantle flow field is consistent with observations from seismic anisotropy. The seismic anisotropy observations constrain the shape of the eastern slab edge and require non-Newtonian mantle rheology. The incorporation of the non-Newtonian viscosity results in mantle viscosities of 10~(17) to 10~(18) Pa s in regions of high strain rate (10~(12) s~(-1)), and this low viscosity enables the mantle flow field to decouple partially from the motion of the surface plates. These results imply local rapid transport of geochemical signatures through subduction zones and that the internal deformation of slabs decreases the slab-pull force available to drive subducting plates.
机译：地表构造板块的运动方向与由地震各向异性推断出的地幔流场在全球范围内具有很好的相关性，这表明地幔与地壳板块之间存在大规模耦合。在俯冲带，拟合度通常很差，但是，在地震各向异性的区域观测中，地幔流动的方向不平行于板运动，可能比板运动快几倍。在这里，我们为阿拉斯加俯冲转换系统提供了具有实际平板几何形状的浮力驱动变形的三维数值模型，并使用它们来确定这种区域解耦的起源。我们发现，在俯冲带边缘附近，地幔流动速度的大小可以是平板运动的十倍以上，而平板速度与板块运动是一致的，而复杂的地幔流场与地震各向异性的观测结果是一致的。地震各向异性的观测结果限制了东部平板边缘的形状，因此需要非牛顿地幔流变学。非牛顿粘度的引入导致在高应变速率（10〜（12）s〜（-1））区域的地幔粘度为10〜（17）至10〜（18）Pa s。使地幔流场从面板的运动中分离出来。这些结果暗示地球化学特征通过俯冲带进行局部快速输送，并且平板的内部变形减小了可用于驱动俯冲板的平板拉力。

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  • 来源
    《Nature》 |2010年第7296期|p.338-341|共4页
  • 作者

    Margarete A. Jadamec; Magali I. Billen;

  • 作者单位

    Department of Geology, University of California, Davis, California 95616, USA School of Mathematical Sciences & School of Geosciences, Monash University, Clayton, Victoria 3800, Australia;

    Department of Geology, University of California, Davis, California 95616, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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