MagmaCourse: Fluid pathways below the Eger Rift constrained by numerical and analog simulations.

这一提议的目的是获得与观测一致的深部流体路径的概念模型，特别是对流体、矿化和岩浆存在敏感的地震和大地电磁观测(Q1和Q2)。我们计划首次将力学模型(数值模拟和互补的实验室模拟模型)与受约束的MT反演和地球化学模型结合在一个循环过程中，其中一个模型的输出用作下一步的输入。沃格特兰/西波希米亚地震群是地壳地震活动的一个突出例子，其中流体起主要作用，并与欧洲为数不多的板内地震活动区之一有关。许多争论和悬而未决的问题都围绕着这些震群，这里我们列出了一个选择：Q1)该地区大陆内构造所起的作用。该地区是一条被新生代后造山伸展作用重新激活的古生代缝合线，形成了长300公里、宽50公里的埃格地堑和切布-多马兹利斯地块。丰富的、空间分布的碱性火山活动与这一地区有关。是什么控制了火山活动及其地球化学的空间分布？地震活动和火山活动是如何联系在一起的？同位素比值表明，以富CO2云母和热液活动的形式到达地表的高CO2通量直接来自上地幔。岩浆和其他流体遵循的路径是什么？控制它们的因素是什么？流体在运移过程中的组成和物理化学性质是什么？Q3)流体进入原有断层的通道作用和地震活动的触发因素。在过去的30年里，该地区发生了多次蜂群。进入先前存在的断裂带的加压流体的力学是什么？支持流体运动的机制是什么？到达孕震体积的地壳流体的成分是什么？它们的物理性质是什么？它们是如何随时间演变的？流体-岩石耦合如何将流体压力转化为岩石应力？这些相互关联的问题代表了ICDP Eger Rift项目的关键问题。我们将开发新的数值和模拟力学和地球化学模型，并使用它们来约束现有2D反演模型的模型空间，这些模型现在不是唯一的。我们将使用现有的地壳深部地震数据和沿两条垂直剖面(2015年秋季)和密集网格(2016年春季)在震群和莫夫岩地区获得的大地电磁测深数据。与MT小组的密切合作旨在直接复核个人假设，这是新颖和开创性的。将在后续提案中讨论孕震带地震活动的产生问题。

The aim of this proposal is to obtain a conceptual model of deep fluid pathways consistent with observations, especially seismic and magnetotelluric (MT) observations that are sensitive to fluids, mineralization and presence of magma (Q1 and Q2). We plan for the first time to combine mechanical models (numerical simulations and complementary laboratory analog models) with constrained MT inversions and geochemical models in a loop process where the output of one model is used as input for the next step.The Vogtland/West Bohemia seismic swarms are a prominent example of crustal seismicity where fluids are playing a primary role, and relate to one of the few intra-plate seismically active regions of Europe. Many debates and unanswered questions revolve around these seismic swarms, here we list a selection: Q1) The role played by the intra-continental tectonics of the area. The area is a Paleozoic suture that was reactivated by Cenozoic post-orogenic extension, creating the 300km long and 50km wide Eger Graben and the Cheb-Domazlice Graben. Abundant, spatially distributed alkaline volcanism is associated with this area. What controls the spatial distribution of the volcanism and its geochemistry? How are seismicity and volcanism linked?Q2) Deep fluid pathways. Isotope ratios reveal that the high CO2 flux, reaching the surface in the form of CO2 rich mofettes and hydrothermal activity, originates directly from the upper mantle. What are the pathways followed by the magma and by the other fluids, and what factors are controlling them? What are the composition and the physicochemical properties of the fluids while they are migrating?Q3) Channeling of the fluids into pre-existing faults and the triggering factors for the seismicity. In the last 30 years multiple swarms have occurred in the area. What is the mechanics of the pressurized fluids entering into the pre-existing fault zone? What are the mechanisms supporting fluid movement? What is the composition of the crustal fluids reaching the seismogenic volume? What are their physical properties, and how do they evolve with time? How is the fluid-rock coupling converting fluid pressurization into rock stressing?These interconnected questions represent key questions for the ICDP Eger Rift project. We will develop new numerical and analog mechanical and geochemical models, and use them to constrain the model space of existing 2D inversion models, that are now non-unique. We will use available deep crustal seismic data and MT data acquired along 2 perpendicular profiles (autumn 2015) and on a dense grid (spring 2016) in the area of earthquake swarms and mofettes. A close cooperation with the MT group aimed at directly countercheck individual assumptions is novel and pioneering. The generation of the seismicity in the seismogenic zone will be addressed in a follow-up proposal.