MagmaKammern: Surface Loading Changes as Top-Down Controls on Magma Reservoir Formation

在这个项目中，我们将揭示火山的形状（成层火山与破火山口）和生长历史如何影响岩浆储存的深度和结构。我们将通过岩脉扩展的数值和模拟模型来模拟地壳中岩浆的上升路径。先前的研究已经表明，火山建筑物的负荷使主应力旋转，从而引导上升的岩脉集中在建筑物下方。地表大规模破坏事件，如破火山口的形成，反而会导致上升岩脉的散焦，引导它们从火山中心（例如在边缘下）喷发。在这个项目中，我们将模拟在不同的构造背景下，在成层火山和破火山口下面的岩浆房的增量增长。我们将研究不同形状的火山和典型的加载历史和周期如何影响岩脉逐渐累积成岩浆库。我们将把模型结果与观测结果联系起来，包括地壳形变、地震学、大地电磁学和岩石学。为此，我们将模拟堤坝相继上升，考虑堤坝-水库和堤坝-堤坝的相互作用，背景应力由表面载荷和构造应力引起。当岩墙距离较远时，地表荷载和构造应力将起主导作用。一旦堤坝接近存储区，由先前被阻止的堤坝引起的应力将成比例地更强，并且堤坝将偏离。堤防相互作用和表面荷载的影响在过去已经被单独研究，但从来没有一起考虑。储层形成的问题已经在岩石学、地球化学、热发展和岩石流变学方面得到了解决，但从未机械地包括控制岩脉的应力。然而，地壳变形研究显示了广泛的模式，与表面负荷对岩浆储存系统的形状和深度起着强有力的控制作用的想法非常吻合：破火山口与岩床或顶部平坦的水库有关，而成层火山则与垂直发育的水库有关，如椭球体。我们将通过我们的模拟深入到这个过程的根源。我们的新模型将应用于不同构造环境中的成层火山和破火山口，以比较模型结果与观测结果。我们的项目将打开一个新的视角，对岩浆储层的研究，从来没有被调查过：自上而下的控制表面质量变化的形状和深度的浅岩浆储存区。

In this project, we will reveal how a volcano's shape (stratovolcano vs. caldera) and growth history influences the depth and construction of magma storage. We will simulate the ascent pathways of magma in the crust by means of numerical and analog models of dike propagation. Previous studies have shown that the loading of a volcanic edifice rotates the principal stresses, thereby steering ascending dikes to focus below the edifices. Surface mass destruction events, such as the formation of a caldera, cause instead a de-focusing of ascending dikes, steering them to erupt offset from the center of the volcano (for example under the rims). In this project we will simulate the incremental growth of a magma chamber below a stratovolcano and below a caldera in different tectonic contexts. We will study how the different shapes of volcanoes and typical loading histories and cycles affect the incremental accumulation of dikes into magma reservoirs. We will link the model results to observations including crustal deformation, seismology, magnetotellurics and petrology. To this aim, we will simulate the ascent of dikes one after the other, considering dike-reservoir and dike-dike interaction, with the background stress due to a surface load and tectonic stress. When the dike is distant, the surface loading and tectonic stress will dominate. Once the dike approaches the storage zone, the stress induced by previously arrested dikes will be proportionally stronger and the dikes will deviate. Dike-dike interaction and the effects of surface loads have been studied separately in the past but never taken together. The question of reservoir formation has been addressed in terms of petrology, geochemistry, thermal development and rock rheology, but never mechanically including stresses controlling the dikes. Crustal deformation studies however show broad patterns that fit well with the idea that surface loads play a strong control on the shape and depth of the magma storage system: calderas are related to sills or top-flatted reservoirs, while stratovolcanoes are linked to vertically developed reservoirs such as ellipsoids. We will go to the root of the process with our simulations. Our new models will be applied to stratovolcanoes and calderas in different tectonic environments to compare the model results with observations. Our project will open a new perspective on magma reservoir research that has never been investigated before: the top-down controls of surface mass changes on the shape and depth of shallow magma storage zones.