Exploring fluid-rock interactions along the subduction interface - The record within (ultra)high-pressure metasediments

俯冲界面是前进造山过程中上、下板块的分界带，是变形、流体流动和变质作用的重要场所。这些过程往往是耦合的，并显着修改地壳和地幔岩石，因此影响流变和力学行为的单位在附近的板块界面，从而影响板间耦合和地震活动。在这个项目中，我们将使用一个多学科的方法相结合的微观结构，纹理，岩石学和地质年代学的方法来破译，量化和开发一个模型之间的相互作用的动员和迁移的流体，界面平行剪切带的形成，和变质转变内的流变学弱石英丰富的变质沉积岩岩性沿着蓝片岩榴辉岩相的俯冲界面的一部分。我们将采用相对较新的技术，通过LA-ICP-MS对石榴石进行原位U-Pb年代学，以限制流体-岩石相互作用和流体辅助变质作用阶段的时间和持续时间。（超）高压变质岩的变质沉积物，以前变质和变形沿着一个重要的阿尔卑斯山俯冲界面之间的大陆边缘单位在上盘和下行洋板，现在暴露在内部西阿尔卑斯山的意大利将作为一个例子。

Subduction interfaces are the boundary zones between the downgoing and the upper plate during progressive orogeny and are important sites of deformation, fluid flow and metamorphism. These processes are often coupled and significantly modify crustal and mantle rocks and therefore affect the rheological and mechanical behaviour of units in the vicinity of such plate interfaces, thus influencing interplate coupling and seismicity. In this project, we will use a multidisciplinary approach combining microstructural, textural, petrological and geochronological methods to decipher, quantify and develop a model for the interplay between the mobilization and migration of fluids, the formation of interface-parallel shear zones, and metamorphic transformations within rheologically weak quartz-rich metasedimentary lithologies along the blueschist- to eclogite-facies part of the subduction interface. We will employ the relatively novel technique of in-situ U-Pb geochronology via LA-ICP-MS on garnet to constrain the timing and duration of phases of fluid-rock interactions and fluid-assisted prograde metamorphism. Metasediments of (ultra)high-pressure metamorphic terranes formerly metamorphosed and deformed along an important Alpine subduction interface between continental margin units in the hanging wall and the downgoing oceanic slab and now exposed in the Internal Western Alps of Italy will serve as an example.