During lithospheric extension, localization of deformation often occurs along structural weaknesses inherited from previous tectonic phases. Such weaknesses may occur in both the crust and mantle, but the combined effects of these weaknesses on rift evolution remain poorly understood. Here we present a series of 3D brittle–viscous analogue models to test the interaction between differently oriented weaknesses located in the brittle upper crust and/or upper mantle. We find that crustal weaknesses usually express first at the surface, with the formation of grabens parallel to their orientation; then, structures parallel to the mantle weakness overprint them and often become dominant. Furthermore, the direction of extension exerts minimal control on rift trends when inherited weaknesses are present, which implies that present-day rift orientations are not always indicative of past extension directions. We also suggest that multiphase extension is not required to explain different structural orientations in natural rift systems. The degree of coupling between the mantle and upper crust affects the relative influence of the crustal and mantle weaknesses: low coupling enhances the influence of crustal weaknesses, whereas high coupling enhances the influence of mantle weaknesses. Such coupling may vary over time due to progressive thinning of the lower crustal layer, as well as due to variations in extension velocity. These findings provide a strong incentive to reassess the tectonic history of various natural examples.

中文翻译：

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复杂的裂谷模式，地壳和地幔弱点相互作用的结果，还是多相裂谷？模拟模型的见解

在岩石圈伸展过程中，变形的局部化通常沿着从先前构造阶段继承的结构弱点发生。这种弱点可能同时出现在地壳和地幔中，但这些弱点对裂谷演化的综合影响仍然知之甚少。在这里，我们提出了一系列 3D 脆性-粘性模拟模型，以测试位于脆性上地壳和/或上地幔中不同方向的弱点之间的相互作用。我们发现地壳的弱点通常首先在地表表现出来，地堑的形成平行于它们的方向；然后，与地幔弱点平行的结构覆盖它们并经常成为主导。此外，当存在遗传弱点时，扩展方向对裂痕趋势的控制最小，这意味着当今的裂谷方向并不总是表明过去的延伸方向。我们还建议不需要多相扩展来解释自然裂谷系统中的不同结构方向。地幔与上地壳的耦合程度影响地幔弱点的相对影响：低耦合增强地壳弱点的影响，高耦合增强地幔弱点的影响。由于下地壳层的逐渐变薄以及伸展速度的变化，这种耦合可能会随时间变化。这些发现为重新评估各种自然实例的构造历史提供了强大的动力。我们还建议不需要多相扩展来解释自然裂谷系统中的不同结构方向。地幔与上地壳的耦合程度影响地幔弱点的相对影响：低耦合增强地壳弱点的影响，高耦合增强地幔弱点的影响。由于下地壳层的逐渐变薄以及伸展速度的变化，这种耦合可能会随时间变化。这些发现为重新评估各种自然实例的构造历史提供了强大的动力。我们还建议不需要多相扩展来解释自然裂谷系统中的不同结构方向。地幔与上地壳的耦合程度影响地幔弱点的相对影响：低耦合增强地壳弱点的影响，高耦合增强地幔弱点的影响。由于下地壳层的逐渐变薄以及伸展速度的变化，这种耦合可能会随时间变化。这些发现为重新评估各种自然实例的构造历史提供了强大的动力。低耦合增强了地壳弱点的影响，而高耦合增强了地幔弱点的影响。由于下地壳层的逐渐变薄以及伸展速度的变化，这种耦合可能会随时间变化。这些发现为重新评估各种自然实例的构造历史提供了强大的动力。低耦合增强了地壳弱点的影响，而高耦合增强了地幔弱点的影响。由于下地壳层的逐渐变薄以及伸展速度的变化，这种耦合可能会随时间变化。这些发现为重新评估各种自然实例的构造历史提供了强大的动力。