Metastable olivine wedge and deep dry cold slab beneath southwest Japan
Metastable olivine wedge and deep dry cold slab beneath southwest Japan
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DOI：
10.1016/j.epsl.2011.01.008
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发表时间：
2011-02-15
影响因子：
5.3
通讯作者：
Yoshioka, Shoichi
中科院分区：
文献类型：
--
作者：
Kawakatsu, Hitoshi;Yoshioka, Shoichi
在海沟俯冲的大洋板块进入深部地幔，并在410公里深处遇到一个构造边界，在那里，地幔岩石的主要元素橄榄石转化为密度更高的华德士来石。由于动力学效应，这种转变可能在俯冲板块（板块）最冷的核心内延迟，有人认为亚稳橄榄石可能存在于410公里以上的深处。利用日本的高密度地震台阵资料，我们展示了日本西南部亚稳橄榄石楔（MOW）对应的结构的直接图像。俯冲板的数值模拟，包括水（H2O）对橄榄石wadsleyite转变的动力学效应，表明成像MOW的存在需要少量的水（小于100重量%）。ppm）存在于板幔中，因此是深干冷板。我们推断，水进入深部地幔的运输发生沿着俯冲板片的顶面，但没有显着的量在板片本身。我们还表明，包括660公里的相变动力学的数值模拟可以调和观察到的深凹陷的660公里的不连续性与一个温和的克拉珀龙斜坡。(C)2011 Elsevier B.V.保留所有权利。
Oceanic plates subducted at trenches penetrate into the deep mantle, and encounter a structural boundary at a depth of 410 km where olivine, the dominant element of mantle rocks, transforms into a higher density form wadsleyite. This transformation may be delayed within the coldest core of subducting plates (slabs) due to kinetic effects, and it has been suggested that metastable olivine may persist deeper than 410 km. Using high density seismic array data in Japan, we show the direct image of the structure corresponding to this metastable olivine wedge (MOW) beneath southwest Japan. Numerical simulation of a subducting slab, including the kinetic effect of water (H2O) on the olivine wadsleyite transformation, indicates that the presence of the imaged MOW requires an insignificant amount of water (less than 100 wt. ppm) be present in the slab mantle, thus a deep dry cold slab. We infer that the transportation of water into the deep mantle occurs along the top surface of the subducting slab, but no significant amount within the slab itself. We also demonstrate that a numerical simulation including the kinetics of 660-km phase transformation can reconcile the observed deep depression of the 660-km discontinuity with a gentle Clapeyron slope. (C) 2011 Elsevier B.V. All rights reserved.