Field observations and unmanned aerial vehicle surveys from Caldera Taburiente (La Palma, Canary Islands, Spain) show that pre-existing dykes can capture and re-direct younger ones to form multiple dyke composites. Chill margins suggest that the older dykes were solidified and cooled when this occurred. In one multiple dyke example, an ⁴⁰Ar/³⁹Ar age difference of 200 kyr was determined between co-located dykes. Petrography and geomechanical measurements (ultrasonic pulse and Brazilian disc tests) show that a microscopic preferred alignment of plagioclase laths and sheet-like structures formed by non-randomly distributed vesicles give the solidified dykes anisotropic elastic moduli and fracture toughness. We hypothesize that this anisotropy led to the development of margin-parallel joints within the dykes, during subsequent volcanic loading. Finite element models also suggest that the elastic contrast between solidified dykes and their host rock elevated and re-oriented the stresses that governed subsequent dyke propagation. Thus, the margin-parallel joints, combined with local concentration and rotation of stresses, favored the deflection of subsequent magma-filled fractures by up to 60° to form the multiple dykes. At the edifice scale, the capture and deflection of active intrusions by older ones could change the organization of volcanic magma plumbing systems and cause unexpected propagation paths relative to the regional stress. We suggest that reactivation of older dykes by this mechanism gives the volcanic edifice a structural memory of past stress states, potentially encouraging the re-use of older vents and deflecting intrusions along volcanic rift zones or toward shallow magma reservoirs.

中文翻译：

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岩浆通道的重新激活：实地观察，年代学，地质力学测试和数值模型的启示

来自Caldera Taburiente（西班牙加那利群岛拉帕尔玛岛）的现场观察和无人驾驶飞机调查显示，既有的堤坝可以捕获并重定向较年轻的堤坝，从而形成多个堤坝复合体。寒冷的边缘表明，较旧的堤坝在发生这种情况时已固化并冷却。在一个多堤的例子中，⁴⁰ Ar / ³⁹确定在同一地点的堤坝之间的Ar年龄差异为200 kyr。岩相学和地质力学测量（超声波脉冲和巴西圆盘试验）表明，斜长石板条和由非随机分布的囊泡形成的片状结构的微观优选排列方式赋予了固化的堤坝各向异性弹性模量和断裂韧性。我们假设，这种各向异性导致在随后的火山加载过程中，堤内边缘平行节理的发展。有限元模型还表明，固化的堤坝及其母岩之间的弹性对比提高并重新定向了控制随后堤坝传播的应力。因此，边缘平行接头结合局部集中和应力旋转，有利于随后的岩浆充填裂缝偏转达60°，以形成多个堤坝。在建筑物规模上，较早的活动侵入物的捕获和偏转可能会改变火山岩浆管道系统的组织，并导致相对于区域应力的意外传播路径。我们建议通过这种机制重新激活较旧的堤坝，使火山大厦对过去的应力状态具有结构性记忆，从而可能鼓励重新利用较旧的火山口，并使侵入岩沿裂谷带或浅岩浆储集层偏转。