Numerical simulations of mantle flow around slab edges
Numerical simulations of mantle flow around slab edges
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DOI：
10.1016/j.epsl.2008.10.003
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发表时间：
2009-01
影响因子：
5.3
通讯作者：
S. Honda
中科院分区：
文献类型：
--
作者：
S. Honda
构建了板片边缘周围地幔流的简单运动学动力学模型，以了解那里的流动复杂性。顶部和浅板边界周围小边界区域的流速是通过运动学施加的，以实现类似俯冲的特征，而其他部分的流动则进行动态计算。该板块的几何形状模仿阿留申群岛和堪察加半岛交界处周围的区域，这是收敛变换断层板块边界的例子。在上覆板块几乎静止的简单模型中，一旦板块渗入高粘度层，向下流动遇到阻力，从俯冲板块下方的地幔到相邻板块下方的地幔的横向流动就不太重要了。当海沟前进时，即海沟向上覆板块移动时，也会出现类似的情况。对于后退海沟，即海沟向俯冲板块运动的情况，即使板片穿入高粘层后，也存在侧流，尽管其大小明显小于板块速度。俯冲板块正下方存在的低粘度层可能会促进侧向流动的出现。当高温异常，即俯冲板块运动携带的浮力低粘度块体接近板片时，观察到显着的侧向流动。这些结果可能对亚板地幔中可能存在海沟平行流具有重要意义。
A simple kinematic-dynamic model of mantle flow around the slab-edge is constructed in order to understand the flow complexity there. The flow velocity on the top and the small boundary region around the shallow plate boundary is kinematically imposed in order to achieve a subduction-like feature and the flow in other part is dynamically calculated. The geometry of the plate mimics the region around the junction of Aleutian Islands and Kamchatka, that are examples of the convergent-transform fault plate boundaries. In a simple model in which the overlying plate is almost stationary, the lateral flow from the mantle under the subducting slab to the mantle under the neighboring plate is of minor importance, once the slab penetrates into the high viscosity layer where the downward flow encounters the resistance. Similar situation was found when the trench is advancing, that is, the trench moves toward the overlying plate. For the case with retreating trench, that is, the trench moves toward the subducting plate, a lateral flow exists even after the slab penetrates into the high viscosity layer, although its magnitude is significantly smaller than that of the plate velocity. The presence of a low viscosity layer just beneath the subducting plate may promote the emergence of lateral flow. A significant lateral flow is observed when the high temperature anomaly, that is, buoyant and low viscosity block carried by the movement of subducting plate, approaches the slab. These results may have important implications for the possible existence of trench parallel flow in the sub-slab mantle.