超基性岩体系深部流体与脱水反应的原位实验观测

地球内部的流体对地球内部物质的性质和演化起着不可或缺的作用，可以催化甚至直接参与一些重要的变质反应，例如脱水和脱碳反应。在浅部低压下(例如，<10 kbar)，这些流体的溶质主要是盐类(例如，碱金属氯化物)和气体(例如，CO2)，但在深部高压下还可能涉及到硅酸盐。传统上，对变质流体和反应的实验研究主要是间接分析淬火后的产物，难以获得高温高压下的原位数据。本研究计划利用热液金刚石压腔和拉曼光谱仪原位观测超基性岩蚀变矿物，包括滑石、叶蛇纹石和水镁石参与的矿物-流体相互作用以及脱水反应，获得水溶组分类型和含量、反应边界和反应速率等信息。除了纯水，CO2和NaCl也会作为溶质加入到初始反应流体中。研究结果有望揭示典型流体对蚀变俯冲超基性岩脱水深度和反应动力学的影响，加深我们对深部流体性质及其对变质作用的认识，推动深部流体内洽性热力学数据库的建立。

Fluids play a significant role in regulating the properties and evolution of materials within Earth’s interior. For example, fluids could help increase reaction rates and may be even involved in some important metamorphic reactions such as dehydration and decarbonation reactions. The solutes are usually assumed to be salts (mainly alkali chlorides) and gases (mainly CO2) at relatively lower pressures (e.g. < c.10 kbar), but substantial amounts of host-rock oxide components (mainly silicates and aluminosilicates) are predicted to be dissolved in water at elevated pressure-temperature (P-T) conditions. Traditionally, the composition of high-P-T experimental fluids is indirectly measured from quenched vapors， and in-situ properties are difficult to be obtained. In this study, hydrothermal diamond-anvil cell and Raman spectroscopy will be used to investigate mineral-water interactions and dehydration reactions of some hydrothermally alternated ultramafic minerals, including talc, antigorite, and brucite. The goals are to determine the aqueous species and their concentrations, reaction boundaries, and reaction rates. In addition to pure water, NaCl and CO2 will be added separately into the fluids. The results will reveal the impacts of these typical deep fluids on the dehydration depth and reaction kinetics of hydrothermally alternated ultramafic rocks, improve our knowledge of deep fluids and their roles in dehydration reactions, and promote the establishment of internally consistent thermodynamic dataset for high-P-T aqueous fluids.