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

俯冲界面是前进造山运动中上下板块之间的边界带，是变形、流体流动和变质作用的重要场所。这些过程通常是耦合的，并显著地改变了地壳和地幔岩石，因此影响了这些板块界面附近的单元的流变学和力学行为，从而影响了板块间耦合和地震活动性。在本项目中，我们将采用多学科方法，结合微观构造、结构、岩石学和地质年代学方法，对俯冲界面蓝片岩-榴辉岩相部分流变弱、富含石英的变质沉积岩性中流体的动员和运移、界面平行剪切带的形成以及变质转化之间的相互作用进行解码、量化和开发模型。我们将采用相对新颖的通过LA-ICP-MS对石榴石进行原位U-Pb年代学的技术来限制流体-岩石相互作用和流体辅助渐进变质作用阶段的时间和持续时间。（超）高压变质地体的变质沉积物，以前沿着上壁上大陆边缘单元与下沉洋板之间的一个重要的阿尔卑斯俯冲界面变质变形，现在暴露在意大利西阿尔卑斯内部，就是一个例子。

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.