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.

中文翻译：

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地幔压力和温度下橄榄石的晶间塑性

摘要 富含橄榄石的岩石的延展性对于限制地球上地幔的热对流至关重要。用于位错或扩散蠕变的经典橄榄石流动定律无法解释 GPS 观测到的快速地震后表面位移，这需要比经典定律预测的岩石圈弱得多的岩石圈。在这里，我们将在地幔压力和温度下实验变形的橄榄石聚集体的塑性与单晶的塑性进行比较，并证明根据应力和温度条件，通过晶粒间相互作用调节的应变——这里称为晶间应变——可以是阶数的数量级大于晶内应变，这显着削弱了橄榄石强度。这个结果，沿着地幔地温外推，表明在大部分上地幔中，粒间塑性可能占主导地位。因此，上地幔中富含橄榄石的聚集体的强度可能明显低于基于晶内塑性模型的流动定律预测的。