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，受板块浅部分的脆性过程和较深部分的延展性行为控制。我们回顾了橄榄石延性变形的实验限制，橄榄石是上地幔和岩石圈的主要矿物。橄榄石的变形主要由四种机制组成：低温塑性、位错蠕变、位错容纳的晶界滑动 （GBS） 和扩散容纳的晶界滑动（扩散蠕变）。大部分岩石圈的变形以 GBS 为主，但剪切区（扩散蠕变占主导地位）和脆性-延展性转变（低温塑性可能占主导地位）除外。我们发现，对自然变形岩石的观测与实验约束橄榄石流动定律对地质条件的外推一致，但地球物理观测预测的岩石圈较弱。造成这种差异的原因尚未解决，但可能在于岩石圈最强的脆性-韧性转变过程的不确定性。▪岩石圈地幔的延性变形受橄榄石实验数据的限制。▪橄榄石的变形主要由四种机制组成：低温塑性、位错蠕变、位错容纳的晶界滑动和扩散蠕变。▪对自然变形岩石的观察与从实验条件推断的橄榄石流动规律一致。▪实验预测的岩石圈比地球物理观测更强，可能是由于脆性-韧性过渡中的变形。