Evolution, pattern, and partitioning of deformation during oblique continental rifting: Inferences from lithospheric-scale centrifuge models
Evolution, pattern, and partitioning of deformation during oblique continental rifting: Inferences from lithospheric-scale centrifuge models
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DOI：
10.1029/2009gc002676
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发表时间：
2009-11-26
影响因子：
3.5
通讯作者：
Mulugeta, Genene
中科院分区：
文献类型：
--
作者：
Agostini, Andrea;Corti, Giacomo;Mulugeta, Genene
斜向裂谷作用是通过离心实验来研究的，该实验再现了含有预先存在的软弱带的大陆岩石圈的伸展。在伸展过程中，这种弱点使变形局部化，并通过改变其相对于伸展方向的趋势来获得不同的裂谷韧性。模拟结果表明，变形主要受垂直角α（定义为垂直于裂谷走向的方向与伸展方向之间的夹角）的控制。对于低结晶度（α < 45度），裂陷作用最初的特征是与沉降的裂陷洼地接壤的大型雁列边界断层的活化，没有变形影响裂陷底部。拉张作用的加剧导致边界断层的废弃和断陷内新断层的发育。这些断裂与伸展方向正交，呈雁列状排列，由复杂的转换带连接，具有走滑运动分量。在这些模型中，一个强大的应变分配之间观察到的裂谷边缘，边界断层系统有一个挤压滑动运动，谷底，远离转换区的影响是一个纯粹的伸展。中等倾斜度（α = 45度）仍然导致两阶段的裂谷演化，尽管边界断层活动强烈减少，变形很快转移到裂谷凹陷。故障模式是类似的低渗透率模型，虽然内部故障变得稍微倾斜的正交延伸方向。裂谷边缘和谷底之间的变形分区仍然可以观察到，但不如低变质度裂谷发育。对于高结晶度（α> 45度），没有边界断层形成，并且伸展变形从伸展的早期阶段起就影响裂陷。走滑运动对伸展运动的主导作用导致了斜向走滑和几乎纯走滑断层的发展，斜向裂谷走向和垂直于伸展方向，边缘和裂谷底部之间没有应变分配。这些结果表明，斜重新激活的预先存在的弱点起着重要作用，在控制裂谷的演变，建筑和应变分区，自然斜裂谷的研究结果有显着的相关性。
Oblique rifting is investigated through centrifuge experiments that reproduce extension of a continental lithosphere containing a preexisting weakness zone. During extension, this weakness localizes deformation, and different rift obliquity is obtained by varying its trend with respect to the stretching direction. Model results show that deformation is mostly controlled by the obliquity angle a (defined as the angle between the orthogonal to the rift trend and the extension direction). For low obliquity (alpha < 45 degrees), rifting is initially characterized by activation of large, en echelon boundary faults bordering a subsiding rift depression, with no deformation affecting the rift floor. Increasing extension results in the abandonment of the boundary faults and the development of new faults within the rift depression. These faults are orthogonal to the direction of extension and arranged in two en echelon segments linked by a complex transfer zones, characterized by strike-slip component of motion. In these models, a strong strain partitioning is observed between the rift margins, where the boundary fault systems have an oblique-slip motion, and the valley floor that away from the transfer zones is affected by a pure extension. Moderate obliquity (alpha = 45 degrees) still results in a two-phase rift evolution, although boundary fault activity is strongly reduced, and deformation is soon transferred to the rift depression. The fault pattern is similar to that of low-obliquity models, although internal faults become slightly oblique to the orthogonal to the direction of extension. Deformation partitioning between the rift margins and the valley floor is still observed but is less developed than for low-obliquity rifting. For high obliquity (alpha > 45 degrees), no boundary faults form, and the extensional deformation affects the rift depression since early stages of extension. Dominance of the strike-slip motion over extension leads to the development of oblique-slip and nearly pure strike-slip faults, oblique to both the rift trend and the orthogonal to the extension direction, with no strain partitioning between the margins and the rift floor. These results suggest that oblique reactivation of preexisting weaknesses plays a major role in controlling rift evolution, architecture, and strain partitioning, findings that have a significant relevance for natural oblique rifts.