D/H isotope exchange between electrolyte-bearing C-O-H magmatic fluids: In-situ experiments involving vapors and brines

了解高温高压下H2O的性质对于火山和岩浆过程，以及影响地热能、核废料和化学工程工业的过程都很重要。这项研究使用新开发的新型实验室技术，如热液金刚石砧细胞与拉曼/傅立叶变换红外光谱相结合，将用于在超临界条件下对轻水和重水中气体和金属的溶剂化进行实时测量。该项目将引入新的实验技术，通过在地下地热流体演化和火山岩浆脱气的背景下观察氢的同位素，来了解富电解质超临界流体中溶解的氢气和甲烷的系统。收集到的数据将用于增强地球内部水循环的理论模型。这些实验及其解释还将揭示与地球深层水文循环有关的质量和热量传递，以及地热流体与固体地球的相互作用，这一过程有助于二氧化碳、甲烷和其他气体向大气的流动。这项工作的更广泛影响包括提供高温高压下H2O的基础知识，这对科学和工程的广泛领域有影响，例如化学工程（例如有毒/放射性废物修复，核动力反应堆），物理化学，地球物理，地球化学和能源相关研究。此外，将创建一系列讲座和实验室演示，并向弗吉尼亚州乔治梅森大学的本科生和研究生展示。本科生将有机会通过在华盛顿卡内基学院为期10周的实习项目参与该项目，该项目将在该奖项生效的两年夏季进行。该研究的技术方面涉及研究各种含氢挥发物（H2, CH4, H2O）之间氘和氢同位素的交换。这项工作将在了解火山环境的热状态和岩浆流体来源的背景下检查这些挥发物。例如，来自海水的贫氘盐水有助于洋中脊玄武岩玻璃中富cl熔体包裹体的氢同位素组成。然而，这些盐水的组成是完全不受限制的，这阻碍了追踪海底玄武岩地幔源氢同位素组成的努力。此外，岩浆上升过程中脱气对富Cl、富F流体或含有海水中常见离子（Na/K/Mg/Ca/Cl/F）的水溶液中H2（aq）、CH4（aq）和H2O之间D/H交换的影响目前尚无实验数据。在后一种情况下，将研究这些离子的浓度和静电性质对H2O结构的影响，以及它们如何影响H2和CH4在超临界H2O- d2o混合物中的溶剂化机制和H-D同位素物的溶解度。利用热液金刚石砧细胞和拉曼/傅里叶红外光谱进行现场实时测量。结果将通过GC-TC/ ea -同位素质比谱法来补充，以确定固体介质高压装置实验中在高p / t下平衡的物种之间的总体D/H比和同位素分馏。该研究将补充和支持氢-氢甲烷同位素地球化学的新前沿。

The properties of H2O at high temperatures and pressures are important to know for both volcanic and magmatic processes, as well as for processes that impact the geothermal energy, nuclear waste, and chemical engineering industries. This research, using newly developed, novel laboratory techniques, such as hydrothermal diamond anvil cells coupled with Raman/Fourier Transform Infrared spectroscopy, will be used to make real time measurements of the solvation of gases and metals in light and heavy H2O at supercritical conditions. This project will bring new experimental techniques to bear to understand the systematics of hydrogen gas and methane dissolved in electrolyte-rich supercritical fluids by looking at the isotopes of hydrogen in the context of the evolution of geothermal fluids in the subsurface and the degassing of magmas in volcanoes. Data collected will be used to augment theoretical models of water cycling in Earth's interior. The experiments and their interpretation will also shed light on the mass and heat transfer associated with Earth's deep hydrological cycle as well as the interaction of geothermal fluids with the solid Earth, a process that contributes to the flux of carbon dioxide, methane, and other gases to the atmosphere. Broader impacts of the work include providing fundamental knowledge about H2O at high temperatures and pressures, which has implications for a broad array of fields in science and engineering, such as chemical engineering (e.g. toxic/radioactive waste remediation, nuclear power reactors), physical chemistry, geophysics, geochemistry, and energy-related research. In addition, a series of lectures and lab demonstrations will be created and presented to undergraduate and graduate students at the George Mason University in Virginia. Undergraduates will have an opportunity to be involved in the project through a 10-week internship program at the Carnegie Institute of Washington that will run during the summer both years that the award is active. Technical aspects of the research involve study of the exchange of deuterium and hydrogen isotopes between various hydrogen bearing volatiles (H2, CH4, H2O). The work will examine these volatiles in the context of understanding the thermal regime of volcanic settings and the source of magmatic fluids. For example, deuterium-depleted brines derived from seawater contribute to the hydrogen-isotope composition of Cl-rich melt inclusions in mid-ocean ridge basalt glasses. However, the composition of these brines is completely unconstrained, hindering efforts to trace the hydrogen-isotope composition of the mantle source of seafloor basalts. Furthermore, at present, there are no experimental data to describe the effect of degassing during magma ascent on the D/H exchange between H2(aq), CH4(aq) and H2O dissolved in Cl-rich, F-rich fluids, or aqueous fluids that contain common ions found in seawater (i.e., Na/K/Mg/Ca/Cl/F). In the latter case, the concentration and electrostatic properties of these ions on the structure of H2O and how they affect the solvation mechanism and solubility of H-D isotopologues of H2 and CH4 in supercritical H2O-D2O mixtures will be examined. Measurements will be made in-situ and in real-time by employing hydrothermal diamond-anvil cells and Raman/FTIR spectroscopy. Results will be complemented by the use of GC-TC/EA-Isotope Mass Ratio Spectrometry to determine bulk D/H ratios and isotope fractionations between species equilibrated at high-P/-T during experiments in solid-media high-pressure apparatus. The proposed study will compliment and support the new frontiers of H-D CH4 isotopologue geochemistry.