Olivine intergranular plasticity at mantle pressures and temperatures

IF 2 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Comptes Rendus Geoscience Pub Date : 2019-02-01 DOI:10.1016/j.crte.2018.10.001
Paul Raterron , Caroline Bollinger , Sébastien Merkel
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引用次数: 2

Abstract

The ductile behavior of olivine-rich rocks is critical to constrain thermal convection in the Earth's upper mantle. Classical olivine flow laws for dislocation or diffusion creep fail to explain the fast post-seismic surface displacements observed by GPS, which requires a much weaker lithosphere than predicted by classical laws. Here we compare the plasticity of olivine aggregates deformed experimentally at mantle pressures and temperatures to that of single crystals and demonstrate that, depending on conditions of stress and temperature, strain accommodated through grain-to-grain interactions – here called intergranular strain – can be orders of magnitude larger than intracrystalline strain, which significantly weakens olivine strength. This result, extrapolated along mantle geotherms, suggests that intergranular plasticity could be dominant in most of the upper mantle. Consequently, the strength of olivine-rich aggregates in the upper mantle may be significantly lower than predicted by flow laws based on intracrystalline plasticity models.

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橄榄石在地幔压力和温度下的粒间塑性
富含橄榄石的岩石的延展性对限制地球上地幔的热对流至关重要。位错或扩散蠕变的经典橄榄石流动定律不能解释GPS观测到的快速地震后地表位移,这需要比经典定律预测的岩石圈弱得多的岩石圈。在这里,我们比较了在地幔压力和温度下实验变形的橄榄石聚集体与单晶的塑性,并证明,根据应力和温度的条件,通过晶粒与晶粒相互作用产生的应变(这里称为晶间应变)可能比晶内应变大几个数量级,这大大削弱了橄榄石的强度。这一结果,沿着地幔地热推断,表明在大多数上地幔中,粒间塑性可能占主导地位。因此,上地幔富橄榄石团聚体的强度可能明显低于基于晶内塑性模型的流动规律所预测的强度。
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来源期刊
Comptes Rendus Geoscience
Comptes Rendus Geoscience 地学-地球科学综合
CiteScore
2.80
自引率
14.30%
发文量
68
审稿时长
5.9 weeks
期刊介绍: Created in 1835 by physicist François Arago, then Permanent Secretary, the journal Comptes Rendus de l''Académie des sciences allows researchers to quickly make their work known to the international scientific community. It is divided into seven titles covering the range of scientific research fields: Mathematics, Mechanics, Chemistry, Biology, Geoscience, Physics and Palevol. Each series is led by an editor-in-chief assisted by an editorial committee. Submitted articles are reviewed by two scientists with recognized competence in the field concerned. They can be notes, announcing significant new results, as well as review articles, allowing for a fine-tuning, or even proceedings of symposia and other thematic issues, under the direction of invited editors, French or foreign.
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