Kincaid C, Griffiths R W
Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA.
Nature. 2003 Sep 4;425(6953):58-62. doi: 10.1038/nature01923.
The subduction of oceanic lithosphere plays a key role in plate tectonics, the thermal evolution of the mantle and recycling processes between Earth's interior and surface. Information on mantle flow, thermal conditions and chemical transport in subduction zones come from the geochemistry of arc volcanoes, seismic images and geodynamic models. The majority of this work considers subduction as a two-dimensional process, assuming limited variability in the direction parallel to the trench. In contrast, observationally based models increasingly appeal to three-dimensional flow associated with trench migration and the sinking of oceanic plates with a translational component of motion (rollback). Here we report results from laboratory experiments that reveal fundamental differences in three-dimensional mantle circulation and temperature structure in response to subduction with and without a rollback component. Without rollback motion, flow in the mantle wedge is sluggish, there is no mass flux around the plate and plate edges heat up faster than plate centres. In contrast, during rollback subduction flow is driven around and beneath the sinking plate, velocities increase within the mantle wedge and are focused towards the centre of the plate, and the surface of the plate heats more along the centreline.
大洋岩石圈的俯冲在板块构造、地幔热演化以及地球内部与表面之间的物质循环过程中起着关键作用。俯冲带中地幔流动、热状况和化学物质传输的信息来自于弧火山的地球化学、地震图像和地球动力学模型。这项工作大多将俯冲视为二维过程，假定平行于海沟方向的变化有限。相比之下，基于观测的模型越来越倾向于考虑与海沟迁移以及具有平移运动分量（后撤）的大洋板块下沉相关的三维流动。在此，我们报告了实验室实验的结果，这些结果揭示了有和没有后撤分量的俯冲情况下，三维地幔环流和温度结构的根本差异。没有后撤运动时，地幔楔中的流动迟缓，板块周围没有质量通量，板块边缘比板块中心升温更快。相比之下，在后撤俯冲过程中，流动在下沉板块周围和下方被驱动，地幔楔内的速度增加并集中于板块中心，并且板块表面沿中心线升温更多。
