近日，法国索邦大学Stefan M. Schmalholz团队研究了裂缝边缘的对称性与不对称性：机械各向异性的作用。2025年10月23日出版的《地质学》杂志发表了这项成果。

大陆岩石圈的伸展导致颈缩和破裂，形成从对称到不对称形态变化的共轭裂陷边缘。虽然这种差异通常与岩石圈初始流变学的变化有关，但在单一裂谷系统内对称和不对称边缘之间的沿走向转变指出了额外的控制因素。构造继承，即大陆岩石圈的力学各向异性，通常被认为影响裂谷演化。

研究组提出了新的岩石圈伸展地球动力学模型，该模型结合了继承的力学各向异性主题，即横向各向同性粘塑性流变学与方向矢量方法的耦合。通过系统地改变各向异性强度和初始织物取向，研究组证明单靠力学各向异性就可以解释从对称裂陷到不对称裂陷的转变。在他们的模型中，各向同性材料有利于以纯剪切变形为主的对称裂陷，而各向异性材料有利于以单纯剪切变形为主的非对称裂陷。

这种转变发生在较低的初始织物角度和中等的各向异性强度。该研究结果为对称和非对称共轭边缘的形成提供了一种新颖而有效的机制，并表明构造继承的沿走向变化及其力学各向异性可以在单个裂谷系统中产生截然不同的变形样式。这些发现突出了机械各向异性在塑造裂陷边缘和影响大陆岩石圈构造演化中的关键作用。

附：英文原文

Title: Symmetry versus asymmetry of rifted margins: The role of mechanical anisotropy

Author: Thibault Duretz, Julie Tugend, Geoffroy Mohn, Stefan M. Schmalholz

Issue&Volume: 2025-10-23

Abstract: Continental lithosphere extension leads to necking and breakup, forming conjugate rifted margins that vary from symmetric to asymmetric morphologies. Although such differences are commonly linked to variations in initial lithospheric rheology, along-strike transitions between symmetric and asymmetric margins within single rift systems point to additional controlling factors. Structural inheritance, causing mechanical anisotropy in the continental lithosphere, is commonly suggested to influence rift evolution. Here we present novel geodynamic models of lithospheric extension incorporating inherited mechanical anisotropy using a transversely isotropic visco-plastic rheology coupled to the director vector approach. By systematically varying anisotropy strength and initial fabric orientation, we demonstrate that mechanical anisotropy alone can explain the transition from symmetric to asymmetric rifting. In our models, isotropic materials favor symmetric rifting dominated by pure shear deformation, while anisotropic materials promote asymmetric rifting driven primarily by simple shear. This transition occurs at low initial fabric angles and moderate anisotropy strengths. Our results offer a novel and robust mechanism for the formation of both symmetric and asymmetric conjugate margins and suggest that along-strike variations in structural inheritance—and thus mechanical anisotropy—can produce contrasting deformation styles within a single rift system. These findings highlight the critical role of mechanical anisotropy in shaping rifted margins and influencing the tectonic evolution of continental lithosphere.

DOI: 10.1130/G53383.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53383.1/662106/Symmetry-versus-asymmetry-of-rifted-margins-The