On the relationship between the formation of shear zones and the form of the flow law for rocks undergoing dynamic recrystallization
On the relationship between the formation of shear zones and the form of the flow law for rocks undergoing dynamic recrystallization
复制标题
岩石动态再结晶剪切带形成与流动规律形式的关系
DOI：
10.1016/s0040-1951(98)00261-3
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发表时间：
1999
期刊：
影响因子：
2.9
通讯作者：
E. Rutter
中科院分区：
文献类型：
--
作者：
E. Rutter
高温下岩石中剪切带的形成和维持，当粘性流动以恒定体积发生时，需要应变弱化。几个过程可以导致这种岩石的流动到高应变的应变弱化特性，但是常规的实验岩石力学技术通常不能提供高质量的高应变力学数据。最近的实验数据表明，方解石大理岩的应变弱化伴随着动态重结晶。具有应变指数r的幂律可用于描述流变应力对应变的依赖性，连同由应力指数n描述的应变速率对应力的依赖性的常规描述。应变稳定地局部化到剪切带中有利于r的负值（如r=-0.8）和n的正值（如n=5 ~ 7）。另一个重要的因素是临界应变ε0，用于再结晶的开始（因此应变弱化）。较小的ε0值有利于剪切带的形成。剪切带的形成削弱了它们所在的地壳剖面，但削弱的程度可能不大，可能不超过之前“稳态”流动应力的50%。某些岩石类型，如镁铁质火成岩，可能通过其机械性能比其他岩石（如云母片岩）更容易形成剪切带。它强调的是，提出的分析是基于应变相关的流动法，描述单相动态再结晶的晶界迁移，导致增强恢复，没有任何变化的变形机制。没有考虑到可能的重要影响所产生的激活粒度敏感的流动，或潜在的削弱所产生的同构造变质反应。
The formation and maintenance of shear zones in rocks at high temperatures, when viscous flow takes place at constant volume, requires strain weakening. Several processes can lead to a strain weakening characteristic in the flow of such rocks to high strains, but conventional experimental rock mechanics techniques cannot normally provide high-quality mechanical data to high strains. Recent experimental data for calcite marble have demonstrated strain weakening accompanied by dynamic recrystallization. A power law with strain exponent r can be used to describe the dependence of the flow stress on strain, together with the conventional description of the dependence of strain rate on stress described by a stress exponent n. The stable localization of strain into shear zones is favoured by more negative values of r (e.g. r=−0.8) and more positive values of n (e.g. n=5 to 7). A further important factor is the critical strain, ε0, for the onset of recrystallization (and hence strain weakening). Shear zone formation is favoured by smaller values for ε0. Shear zone formation weakens the crustal section in which they occur, but the amount of weakening may not be great, perhaps no more than 50% of the previous `steady-state' flow stress. Certain rock types, such as mafic igneous rocks, may through their mechanical properties be more susceptible to shear zone formation than others, such as mica schists. It is emphasized that the analysis presented is based upon a strain-dependent flow law that describes single-phase dynamic recrystallization by grain boundary migration that leads to enhanced recovery, without any change in deformation mechanism. No consideration is given to possibly important effects arising from the activation of grain-size-sensitive flow, or to potential weakening effects arising from syntectonic metamorphic reactions.