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

地幔岩石与含水流体的相互作用（即蛇纹岩作用）是一个与构造板块边界有关的广泛的热液过程。通过向地幔岩石中加入大量的水，蛇纹石化导致岩石密度和机械强度的降低。因此，蛇纹岩化作用被认为在大陆的形成和分裂、海底扩张和俯冲中起着重要作用。地幔岩石的水化作用影响了全球挥发物的地球化学循环，尤其是水和二氧化碳，对地球气候、火山弧的地幔融化和俯冲带的地震活动具有强烈的影响。蛇纹石作用贯穿了地球历史的大部分时间，并通过氢气的产生，创造了能够在极端地下环境中支持微生物生命的地球化学条件。尽管它在许多全球地质过程中起着关键作用，但蛇纹石化过程中化学传质与相关岩石体积变化之间的最基本关系仍然很少量化。这个项目旨在提高我们对这些过程的理解。本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射线微断层扫描（micro -CT）和地球化学建模相结合，将流体成分和矿物学的变化与伴随的体积变化（作为时间和温度的函数）联系起来。特别是这个项目将解决蛇纹石化是一个等化学过程还是等体积过程，这是蛇纹石化研究中一个长期存在且争论激烈的问题。本研究的结果将对我们了解蛇纹岩在各种地质背景下的地球化学、侵位和变形具有重要意义。

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.