Subducting-slab transition-zone interaction: Stagnation, penetration and mode switches
Subducting-slab transition-zone interaction: Stagnation, penetration and mode switches
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DOI：
10.1016/j.epsl.2017.02.005
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发表时间：
2017-04-15
影响因子：
5.3
通讯作者：
van Hunen, Jeroen
中科院分区：
文献类型：
--
作者：
Agrusta, Roberto;Goes, Saskia;van Hunen, Jeroen
地震层析成像显示，俯冲板片可以直接沉入下地幔，也可以位于地幔过渡带。此外，一些板块似乎已经从停滞模式转变为穿透模式，反之亦然。我们调查的动态控制这些模式，特别是它们之间的过渡，使用二维自洽的热-机械俯冲模型。我们的模型证实，沟槽移动的能力是在过渡区板坯压扁的关键。在过渡区底部的克拉珀龙斜坡和粘度跳跃的范围内，热的年轻板块（在我们的模型中为2500万年）最有可能渗透，而冷的老板块（15000万年）驱动更多的海沟运动，并趋于停滞。有几种机制能够诱导渗透板停滞：俯冲板块的老化，减少上板强迫，并增加克拉珀龙斜率（例如，由于更多的水化板的到来）。让停滞的板块穿透是更困难的。这可以通过上板块的作用力从自由到静止的瞬间变化，或者克拉珀龙斜率的突然减小来实现。海沟处板块年龄从老到新的快速变化不容易引起穿透。在地球上，俯冲板块的老化（伴随着上板块裂谷）可能是导致板块停滞的最常见机制，而上板块强迫的强烈变化似乎是触发板块穿透所必需的。(C)2017作者由爱思唯尔公司出版
Seismic tomography shows that subducting slabs can either sink straight into the lower mantle, or lie down in the mantle transition zone. Moreover, some slabs seem to have changed mode from stagnation to penetration or vice versa. We investigate the dynamic controls on these modes and particularly the transition between them using 2D self-consistent thermo-mechanical subduction models. Our models confirm that the ability of the trench to move is key for slab flattening in the transition zone. Over a wide range of plausible Clapeyron slopes and viscosity jumps at the base of the transition zone, hot young slabs (25 Myr in our models) are most likely to penetrate, while cold old slabs (150 Myr) drive more trench motion and tend to stagnate. Several mechanisms are able to induce penetrating slabs to stagnate: ageing of the subducting plate, decreasing upper plate forcing, and increasing Clapeyron slope (e.g. due to the arrival of a more hydrated slab). Getting stagnating slabs to penetrate is more difficult. It can be accomplished by an instantaneous change in the forcing of the upper plate from free to motionless, or a sudden decrease in the Clapeyron slope. A rapid change in plate age at the trench from old to young cannot easily induce penetration. On Earth, ageing of the subducting plate (with accompanying upper plate rifting) may be the most common mechanism for causing slab stagnation, while strong changes in upper plate forcing appear required for triggering slab penetration. (C) 2017 The Authors. Published by Elsevier B.V.