Spontaneous generation of ductile shear zones by thermal softening: Localization criterion, 1D to 3D modelling and application to the lithosphere
Spontaneous generation of ductile shear zones by thermal softening: Localization criterion, 1D to 3D modelling and application to the lithosphere
复制标题
通过热软化自发生成延性剪切带：定位准则、1D 到 3D 建模及其在岩石圈中的应用
DOI：
10.1016/j.epsl.2019.05.026
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发表时间：
2019
影响因子：
5.3
通讯作者：
S. Schmalholz
中科院分区：
文献类型：
--
作者：
D. Kiss;Y. Podladchikov;T. Duretz;S. Schmalholz
韧性剪切带的产生对于构造板块边界（例如俯冲带或走滑带）的形成至关重要。然而，延性应变局部化的主要机制仍然存在争议。我们在这里使用一维 (1D)、2D 和 3D 线性和幂律粘性流的热机械数值模拟来研究通过热软化自发生成延性剪切区。所有模型都是速度驱动的。 1D 模型表现出整体简单剪切，而 2D 和 3D 模型表现出整体纯剪切。初始条件包括在其他均质材料中的小温度扰动。我们使用一系列一维模拟来确定一个新的分析公式，该公式可以预测剪切区内的温度演变。这种温度预测仅需要了解边界速度、流动定律和热参数，而不需要有关剪切带本身的先验信息，例如厚度、应力和应变率。该预测对于块状纯剪切和简单剪切中的 1D、2D 和 3D 剪切区域有效。结果表明，如果相对温升> 50°C，剪切加热比传导冷却占主导地位。剪切带引起的温度变化比相应的有限应变变化宽近一个数量级，因此剪切带和围岩之间不会发生明显的温度变化。应用岩石圈岩石的典型流动定律表明，在几厘米的典型板块构造速度下，会发生热软化产生的剪切带。 yr− 1 或应变率在 10− 16 和 10− 14 s− 1 之间。大于 200 MPa 的剪切应力已经可能导致应变局部化。结果表明，热软化是岩石圈自发韧性剪切带产生的可行机制，并且可能是岩石圈应变局部化的主要机制之一。
The generation of ductile shear zones is essential for the formation of tectonic plate boundaries, such as subduction or strike-slip zones. However, the primary mechanism of ductile strain localization is still contentious. We study here the spontaneous generation of ductile shear zones by thermal softening using thermo-mechanical numerical simulations for linear and power-law viscous flow in one-dimension (1D), 2D and 3D. All models are velocity-driven. The 1D model exhibits bulk simple shear whereas the 2D and 3D models exhibit bulk pure shear. The initial conditions include a small temperature perturbation in otherwise homogeneous material. We use a series of 1D simulations to determine a new analytical formula which predicts the temperature evolution inside the shear zone. This temperature prediction requires knowledge of only the boundary velocity, flow law and thermal parameters, but no a priori information about the shear zone itself, such as thickness, stress and strain rate. The prediction is valid for 1D, 2D and 3D shear zones in bulk pure and simple shear. The results show that shear heating dominates over conductive cooling if the relative temperature increase is> 50° C. The temperature variation induced by the shear zone is nearly one order of magnitude wider than the corresponding finite strain variation so that no significant temperature variation occurs between shear zone and wall rock. Applying typical flow laws for lithospheric rocks shows that shear zone generation by thermal softening occurs for typical plate tectonic velocities of few cm. yr− 1 or strain rates between 10− 16 and 10− 14 s− 1. Shear stresses larger than 200 MPa can already cause strain localization. The results indicate that thermal softening is a feasible mechanism for spontaneous ductile shear zone generation in the lithosphere and may be one of the primary mechanisms of lithospheric strain localization.
影响因子：
5.8
作者：
G. Pozzi;N. Paola;S. Nielsen;R. Holdsworth;L. Bowen
通讯作者：
G. Pozzi;N. Paola;S. Nielsen;R. Holdsworth;L. Bowen