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Nature封面故事:地幔对流模型

摘要 : 本期Nature封面所示为地球一个对流模型的粘度场和表面:红色的低粘度区是板块边界,深蓝色的高粘度区是大陆。

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本期Nature封面所示为地球一个对流模型的粘度场和表面:红色的低粘度区是板块边界,深蓝色的高粘度区是大陆。内部用红色表示热点,用蓝色表示消减带。地球的亚表层以由各种不同大小和形状的构造板块或岩石圈板块构成的一个连锁网络形式出现。地幔流动与地质构造之间之联系的性质以及板块布局的起源在很大程度上仍不知道。Claire Mallard等人建立了具有类似板块行为的地幔对流的电脑模型,并用它们生成了通过时间投射板块边界网络的一系列 “虚拟地球”。这些模型表明,大板块的布局是由消减板块之间的间距控制的,由沟槽(trenches)的弯曲造成的应力将板块分解成较小的碎片,这可解释为什么小弧后板块(back-arc plates)的迅速演变反映了在重大板块构造重组期间板块运动的剧烈变化。封面图片:C. Mallard等。

原文链接:

Subduction controls the distribution and fragmentation of Earth’s tectonic plates

原文摘要:

The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates1 of similar sizes and a population of smaller plates whose areas follow a fractal distribution2, 3. The reconstruction of global tectonics during the past 200 million years4 suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies3, 5, 6, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates7, 8 reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

来源: Nature 浏览次数:0

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