Quantifying the Volume Changes During Serpentinization of Peridotite using Hydrothermal Laboratory Experiments and X-ray Microtomography

地幔岩石与水流体的相互作用(即蛇纹岩化)是与构造板块边界有关的广泛的热液过程。通过向地幔岩石中添加大量的水，蛇纹岩作用会导致岩石密度和机械强度的下降。因此，蛇纹岩作用被认为在大陆的形成和解体、海底扩张和俯冲中发挥了重要作用。地幔岩石的水化作用影响了挥发物的全球地球化学循环，最主要的是水和二氧化碳，对地球气候、火山弧中的地幔熔融和俯冲带的地震活动具有强烈的影响。蛇纹岩作用在地球历史的大部分时间里都在进行，通过产生氢气，创造了能够支持极端地下环境中微生物生命的地球化学条件。尽管它在一些全球地质过程中发挥了关键作用，但蛇纹岩作用过程中的化学质量转移与岩石体积相关变化之间的最基本关系仍然没有得到很好的量化。这个项目旨在提高我们对这些过程的理解。这项研究的总体目标是利用热液实验室实验、矿物和流体分析、X射线显微断层扫描(µ-CT)和地球化学模拟相结合的方法，将流体成分和矿物学的变化与伴随的体积随时间和温度的变化联系起来。特别是，这个项目将解决蛇纹岩作用是一个等化学过程还是等体积过程，这是蛇纹岩作用研究中一个长期和激烈争论的问题。这项研究的结果将对我们在广泛的地质环境中理解蛇纹岩的地球化学、侵位和变形具有重要的意义。

The interaction of mantle rocks with aqueous fluids (i.e. serpentinization) is a widespread hydrothermal process associated with tectonic plate boundaries. By adding significant amounts of water to mantle rocks, serpentinization causes a decrease in rock density and mechanical strength. As a result serpentinization is believed to play a major role in the formation and breakup of continents, seafloor spreading and subduction. The hydration of mantle rocks impacts the global geochemical cycles of volatiles, most notably water and carbon dioxide, with strong implications for Earth's climate, mantle melting in volcanic arcs and the seismicity of subduction zones. Serpentinization has operated throughout most of Earth's history and has, via the production of hydrogen, created geochemical conditions capable of supporting microbial life in extreme subsurface environments. Despite its key role in a number of global geological processes, the most basic relations between chemical mass transfer during serpentinization and associated changes in rock volume have remained poorly quantified. This project is designed to improve our understanding of these processes. The overall objective of this research is to link changes in fluid composition and mineralogy to concomitant changes in volume as a function of time and temperature using a combination of hydrothermal laboratory experiments, mineral and fluid analysis, X-ray microtomography (µ-CT), and geochemical modeling. In particular this project will resolve whether serpentinization can be regarded as an isochemical or an isovolumetric process, a long-standing and strongly debated question in serpentinization research. The results of this study will have important ramifications for our understanding of the geochemistry, emplacement and deformation of serpentinite in a wide range of geological settings.