The strength of lithospheric plates is a central component of plate tectonics, governed by brittle processes in the shallow portion of the plate and ductile behavior in the deeper portion. We review experimental constraints on ductile deformation of olivine, the main mineral in the upper mantle and thus the lithosphere. Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding (GBS), and diffusion-accommodated grain-boundary sliding (diffusion creep). Deformation in most of the lithosphere is dominated by GBS, except in shear zones—in which diffusion creep dominates—and in the brittle-ductile transition—in which low-temperature plasticity may dominate. We find that observations from naturally deformed rocks are consistent with extrapolation of the experimentally constrained olivine flow laws to geological conditions but that geophysical observations predict a weaker lithosphere. The causes of this discrepancy are unresolved but likely reside in the uncertainty surrounding processes in the brittle-ductile transition, at which the lithosphere is strongest. ▪ Ductile deformation of the lithospheric mantle is constrained by experimental data for olivine. ▪ Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding, and diffusion creep. ▪ Observations of naturally deformed rocks are consistent with extrapolation of olivine flow laws from experimental conditions. ▪ Experiments predict stronger lithosphere than geophysical observations, likely due to gaps in constraints on deformation in the brittle-ductile transition.

中文翻译：

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岩石圈地幔的延性变形


岩石圈板块的强度是板块构造的核心组成部分，由板块浅部的脆性过程和较深部分的延性行为控制。我们回顾了橄榄石韧性变形的实验限制，橄榄石是上地幔乃至岩石圈的主要矿物。橄榄石通过四种主要机制变形：低温塑性、位错蠕变、位错适应晶界滑动（GBS）和扩散适应晶界滑动（扩散蠕变）。大部分岩石圈的变形主要由 GBS 主导，但剪切区除外（其中扩散蠕变占主导地位）和脆性转变区（其中低温塑性可能占主导地位）。我们发现，自然变形岩石的观测结果与将实验约束的橄榄石流动定律外推到地质条件一致，但地球物理观测结果预测岩石圈较弱。这种差异的原因尚未解决，但可能在于脆性转变过程的不确定性，此时岩石圈最强。 ▪ 岩石圈地幔的延性变形受到橄​​榄石实验数据的限制。 ▪ 橄榄石通过四种主要机制变形：低温塑性、位错蠕变、位错适应晶界滑动和扩散蠕变。 ▪ 对自然变形岩石的观察结果与从实验条件推断出的橄榄石流动定律一致。 ▪ 实验预测岩石圈比地球物理观测结果更强，这可能是由于脆性转变过程中变形约束的差距。