For magma chambers to form or volcanic eruptions to occur magma must propagate through the crust as dikes, inclined sheets and sills. Most models that investigate magma paths assume the crust to be either homogeneous or horizontally layered, often composed of rocks of contrasting mechanical properties. In regions that have experienced orogenesis, like the Andes, the crust has been deformed over several million years, resulting in rock layers that are commonly folded and steeply dipping. The assumption of homogeneous properties or horizontal layering then does not capture all of the potential magma path-crustal interactions. Here we tackle this problem by determining the effect of a crust made of steeply inclined layers in which sills and inclined sheets are emplaced. We combine field observations from a sill emplaced in the core of an anticlinal fold at El Juncal in the Chilean Central Andes, including lithologies, sill and fold limbs attitude, length and thickness with a suite of finite element method models to explore the mechanical interactions between inclined layers and magma paths. Our results demonstrate that the properties of the host rock layers as well as the contacts between the layers and the geometry of crustal structures all play an important role in magma propagation and emplacement at shallow levels. Sill propagation and emplacement in heterogeneous and anisotropic crustal segments change the crustal stress field promoting sill arrest, deflection or further propagation. Specifically, sills are more likely to be deflected when encountering shallow dipping layers rather than steeply dipping layers of a fold. Mechanically weak contacts encourage sill deflection due to the related rotation of the stress field and this effect is attenuated when the folded layers are steeper. These processes may change the amount and style of recorded surface deformation, with implications for monitoring of active volcanoes.

岩浆房的形成或火山喷发的发生，岩浆必须以岩脉、倾斜的薄片和岩床的形式穿过地壳传播。大多数研究岩浆路径的模型都假设地壳要么是均质的，要么是水平分层的，通常由具有不同机械特性的岩石组成。在经历过造山作用的地区，如安第斯山脉，地壳已经变形了几百万年，导致岩层通常折叠并急剧倾斜。均匀特性或水平分层的假设并没有捕捉到所有潜在的岩浆路径-地壳相互作用。在这里，我们通过确定由陡峭倾斜层组成的地壳的影响来解决这个问题，其中放置了门槛和倾斜的薄板。我们将来自位于智利中部安第斯山脉 El Juncal 背斜褶皱核心中的窗台的现场观测结果，包括岩性、窗台和褶皱肢的姿态、长度和厚度与一套有限元方法模型相结合，以探索之间的机械相互作用倾斜的层和岩浆路径。我们的研究结果表明，主岩层的性质以及层间接触和地壳结构的几何形状都在浅层岩浆传播和侵位中起着重要作用。异质和各向异性地壳段中的地基扩展和就位改变了地壳应力场，促进了地基停滞、偏转或进一步扩展。具体来说，当遇到浅的倾斜层而不是褶皱的陡峭的倾斜层时，门槛更有可能被偏转。由于应力场的相关旋转，机械弱接触会导致门槛偏转，当折叠层更陡峭时，这种影响会减弱。这些过程可能会改变记录的地表变形的数量和类型，从而对活火山的监测产生影响。