Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins
Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins
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弯曲造山带、弧后盆地以及不规则大陆边缘碰撞造成的仰冲
作者：
Schliffke N
大陆碰撞通常涉及高度弯曲的被动板块边缘，导致穿时大陆俯冲在海沟回滚。这些系统可能具有弧后伸展和蛇绿岩仰冲作用，发生在初始碰撞之后。现代的例子包括阿尔沃兰弧和班达弧。古老的系统包括纽芬兰和挪威的加里东。虽然外部力量或预先存在的弱点，经常调用，我们认为，蛇绿岩仰冲同样可以造成内部应力积累碰撞过程中。在这里，我们模拟碰撞与不规则的俯冲大陆边缘的三维（3-D）热力学模型，并使用所产生的应力场的演变，以了解由此产生的地质过程。结果表明，张应力是如何局部化的覆盖板在历时开始的碰撞。这些应力使上覆板块变薄，并可能打开弧后扩张中心。沿着整个海沟的碰撞迅速发生，扩张中心反转，蛇绿岩仰冲，上覆板块受到挤压。这些模型显示了不规则大陆边缘的俯冲如何形成高度弯曲的造山带。在这一机制下，弧后大洋岩石圈仰冲作用是在大陆碰撞过程中，从一个给定的初始边缘几何形状自然演化而来的。
Continental collisions commonly involve highly curved passive plate margins, leading to diachronous continental subduction during trench rollback. Such systems may feature back-arc extension and ophiolite obduction postdating initial collision. Modern examples include the Alboran and Banda arcs. Ancient systems include the Newfoundland and Norwegian Caledonides. While external forces or preexisting weaknesses are often invoked, we suggest that ophiolite obduction can equally be caused by internal stress buildup during collision. Here, we modeled collision with an irregular subducting continental margin in three-dimensional (3-D) thermo-mechanical models and used the generated stress field evolution to understand resulting geologic processes. Results show how tensional stresses are localized in the overriding plate during the diachronous onset of collision. These stresses thin the overriding plate and may open a back-arc spreading center. Collision along the entire trench follows rapidly, with inversion of this spreading center, ophiolite obduction, and compression in the overriding plate. The models show how subduction of an irregular continental margin can form a highly curved orogenic belt. With this mechanism, obduction of back-arc oceanic lithosphere naturally evolves from a given initial margin geometry during continental collision.