Estimate of subduction rate of island arcs to the deep mantle
Estimate of subduction rate of island arcs to the deep mantle
复制标题
岛弧向地幔深部俯冲速率的估计
DOI：
10.1002/2016jb013119
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
and Masanori Kameyama
中科院分区：
文献类型：
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作者：
Hiroki Ichikawa;Shinji Yamamoto;Kenji Kawai;and Masanori Kameyama
最近的地质观测支持一些大洋弧俯冲到地幔中。例如，伊豆-小笠原弧被认为是部分俯冲到日本本州岛之下，尽管它的密度低于周围的地幔，在17 Ma与本州岛垂直碰撞后。地震测量已经澄清了弧的内部结构，包括玄武质和玻安质上地壳，长英质中地壳，中间上-下地壳和镁铁质下地壳。这一结构向北延伸并向本州移动。在这些组成部分中，部分中地壳、中间上-下地壳和下地壳被认为是俯冲的。为了估算大洋弧中花岗岩类物质向深部地幔的俯冲速率，本文采用有限元方法对大洋弧俯冲过程进行了数值模拟，并研究了弧的大小、形状和板片温度对俯冲过程的影响。结果表明，俯冲速率在很大程度上取决于俯冲弧的几何形状或俯冲板片的温度剖面。当弧的大小或板片的温度较小时，俯冲速率增大，由于向上的浮力和向下的粘滞阻力之间的竞争。结果还表明，当俯冲板片的温度处于通常值时，与伊豆-小笠原弧大小相当的洋弧中约有20%的长英质地壳物质可以俯冲到深部地幔中。
Recent geological observations support the subduction of some oceanic arcs into the mantle. For example, the Izu‐Bonin arc is considered to be partially subducting underneath the island of Honshu, Japan, despite its lower density than that of surrounding mantle, after the vertical collision with Honshu at ~17 Ma. Seismological surveys have clarified the internal structure of the arc, which consists of the basaltic and boninitic upper crust, the felsic middle crust, the intermediate upper‐lower crust, and the mafic lower crust. This structure extends and moves northward toward Honshu. Among these components, part of the middle, the intermediate upper‐lower, and the lower crust is thought to be subducting. Here in order to estimate the subduction rate of granitic materials in oceanic arcs to the deep mantle, we have conducted numerical simulations of the subduction of arcs based on the finite element method and investigated the effect of arcs' sizes and shapes and slab temperature. The results show that the subduction rate heavily depends on the geometry of the arcs or temperature profiles of the subducting slabs. When the size of the arc or the temperature of the slab is smaller, the subduction rate grows larger owing to competition between upward buoyancy and downward viscous drag from slabs. The results also show that about 20% of the felsic crust materials in oceanic arcs that are comparable in size to the Izu‐Bonin arc can be subducted into the deep mantle when the temperature of the subducting slab is of the usual value.