Macroscopic strength of oceanic lithosphere revealed by ubiquitous fracture-zone instabilities
Macroscopic strength of oceanic lithosphere revealed by ubiquitous fracture-zone instabilities
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普遍存在的断裂带不稳定性揭示了海洋岩石圈的宏观强度
DOI：
10.1016/j.epsl.2016.05.027
复制
发表时间：
2016
影响因子：
5.3
通讯作者：
J. Korenaga
中科院分区：
文献类型：
--
作者：
C. Cadio;J. Korenaga
板块构造的起源是地球和行星科学中最基本的问题之一。实验室实验表明，硅酸盐岩石的粘度是如此强烈地依赖于温度，以至于整个地球表面应该是一个固定的刚性板块。然而，海洋岩石圈的流变学仍然知之甚少，对于粘性在场尺度上的温度依赖性也没有什么限制。本文报道了一种新的基于大洋断裂带大地水准面的观测约束。我们识别了大量明显的小尺度大地水准面异常，这些异常不能用标准的大洋岩石圈演化模型来解释，并用一种新的贝叶斯反演方法估计了它们的源密度扰动。我们的结果表明，它们很可能是由涉及∼300K±100K温度扰动的小尺度对流引起的。这种温度反差要求地幔粘性活化能在扩散蠕变时低至100±50kJ·−-1，在位错蠕变时低至225±112kJ·mol·−-1，大大减少了大洋岩石圈最坚硬部分的厚度。因此，大洋岩石圈可能比之前认为的更容易破裂和弯曲，从而促进了板块构造的运行。
The origin of plate tectonics is one of the most fundamental issues in earth and planetary sciences. Laboratory experiments indicate that the viscosity of silicate rocks is so strongly temperature-dependent that the entire surface of the Earth should be one immobile rigid plate. The rheology of oceanic lithosphere is, however, still poorly understood, and there exist few constraints on the temperature dependency of viscosity on the field scale. Here we report a new kind of observational constraint based on the geoid along oceanic fracture zones. We identify a large number of conspicuous small-scale geoid anomalies, which cannot be explained by the standard evolution model of oceanic lithosphere, and estimate their source density perturbations using a new Bayesian inversion method. Our results suggest that they are caused most likely by small-scale convection involving temperature perturbations of∼ 300 K±100 K. Such thermal contrast requires the activation energy of mantle viscosity to be as low as 100±50 kJ mol− 1 in case of diffusion creep, and 225±112 kJ mol− 1 in case of dislocation creep, substantially reducing the thickness of the stiffest part of oceanic lithosphere. Oceanic lithosphere may thus be broken and bent much more easily than previously thought, facilitating the operation of plate tectonics.
大地水准面异常的定位和海洋岩石圈的演化：门多西诺断裂带的案例研究
DOI：
--
发表时间：
2012
期刊：
AGU Fall Meeting Abstracts
影响因子：
--
作者：
Korenaga J.
通讯作者：
Korenaga J.