Strain Localization at Constant Strain Rate and Changing Stress Conditions: Implications for Plate Boundary Processes in the Upper Mantle
Strain Localization at Constant Strain Rate and Changing Stress Conditions: Implications for Plate Boundary Processes in the Upper Mantle
复制标题
恒定应变率和变化应力条件下的应变定位：对上地幔板块边界过程的影响
作者：
J. Newman;V. Chatzaras;B. Tikoff;J. Wijbrans;W. Lamb;M. Drury
我们介绍了来自法国比利牛斯山特塞尔地块的天然变形剪切带的结果，该结果直接涉及应变局部化的过程，这是过去40年来构造地质学家一直在研究的话题。古珊瑚测量学表明，差异应力在空间上是可变的，在折返过程中也是在时间上变化的。然而，我们也计算了应变率，尽管应力发生变化，但应变率保持不变。这一结果似乎与最近在单相(橄榄石)岩石上进行的实验变形不一致，后者表明应变局部化主要是由于恒定应力的结果。我们假设，在都灵地块和许多天然剪切带中，应变局部化是反应的结果，这些反应减小了颗粒尺寸，促进了对颗粒尺寸敏感的变形机制的激活。从构造学的角度来看，这一研究表明，在特定的板块边界上，变形速率相对均匀。然而，为了适应这种变形，应力会发生变化。这一观点与板块边界处的变形是一致的，但不是我们解释应变局部化的典型方式。
We present results from a natural deformed shear zone in the Turon de Técouère massif of the French Pyrenees that directly addresses the processes involved in strain localization, a topic that has been investigated for the last 40 years by structural geologists. Paleopiezometry indicates that differential stresses are variable both spatially across the zone, and temporally during exhumation. We have, however, also calculated strain rate, which remains constant despite changes in stress. This result appears to be at odds with recent experimental deformation on monophase (olivine) rocks, which indicate that strain localization occurs dominantly as a result of constant stress. We hypothesize that in the Turon de Técouère massif—and many natural shear zones—strain localization occurs as a result of reactions, which decrease the grain size and promote the activation of grain size sensitive deformation mechanisms. From a tectonics perspective, this study indicates that the deformation rate in a particular plate boundary is relatively uniform. Stress, however, varies to accommodate this deformation. This viewpoint is consistent with deformation at a plate boundary, but it is not the typical way in which we interpret strain localization.