Deuterium\Hydrogen Partitioning Between C-O-H species in Silicate Melts and Fluids: An In-Situ Experimental Study at High Pressure and Temperature

水对地球上发生的各种地质过程都是必不可少的。例如，水的循环控制着岩石圈和水圈之间的热量和质量流量。然而，为了更好地了解地球内部的水循环，重要的是要限制氢和重氢(添加了中子的氢？重氢？)等化学成分的分布。它们构成了溶解在火山玻璃和矿物中的水。在这些相中，富氢和富氢分子的浓度可能限制了观测到的地幔和大洋H2O储集层之间氢-氚组成的差异，以及俯冲带对地幔-水循环的贡献。不同储水层之间氢/氚丰度的差异表明，地幔中的水循环并不广泛，或者氢和氚在高温下溶解在矿物、熔体和流体中时反应不同。因此，实验结果将有助于揭示深藏在地球内部的水的命运，并促进我们目前对行星演化和形成的理解。在这项研究中，我们将在反映下地壳和上地幔条件的压力和温度下，研究硅酸盐熔体和流体中氢/氢分配与C-O-H挥发分形态的关系。我们将利用拉曼光谱和红外光谱，在高温高压下的一系列水热金刚石压腔实验中，原位研究溶解在熔体和共存流体中的甲烷、氢和水的H-D同位素的相对分布。对淬火熔体的1H/2H核磁共振和TC/EA-同位素质量比谱的使用将补充这些实验。实验结果将有助于我们限制同位素交换反应作为元素形态和熔体、晶相和水溶液之间分配的函数。振动光谱用于原位和实时测量同位素分子的新用途可以扩展到其他应用，包括矿物物理、地球化学和与能源相关的研究。一名本科生将参加该项目第二年和第三年设立的为期10周的实习计划。这项研究也将支持M.Sc。乔治梅森大学一名研究生的论文。

Water is essential to a wide range of geological processes occurring on Earth. The cycling of water, for example, governs the flux of heat and mass between the lithosphere and hydrosphere. To better understand the water cycle in the Earth?s interior, however, it is important to constrain the distribution of chemical components such as hydrogen and deuterium (hydrogen with an added neutron ? ?heavy hydrogen?) that constitute the water dissolved in volcanic glasses and minerals. The concentration of deuterium- and hydrogen-rich molecules in these phases likely constrain the observed differences on the hydrogen-deuterium composition between mantle and oceanic H2O reservoir, as well as the subduction zone contributions to the mantle-water cycle. These differences in the abundance of hydrogen/deuterium between water reservoirs implies that cycling of water in the mantle is not extensive or that hydrogen and deuterium react differently at high temperatures when dissolved in minerals, melts and fluids. Experimental results will, thus, shed light on the fate of water that resides deep in the Earth?s interior and promote our current understanding of planetary evolution and formation.In this study, we will investigate the relationship between deuterium/hydrogen partitioning and speciation of C-O-H volatiles in silicate melts and fluids at pressures and temperatures reflecting lower crust and upper mantle conditions. We will study the relative distribution of H-D isotopologues of methane, hydrogen, and water dissolved in melts and coexisting fluids in-situ by Raman and infrared spectroscopy in a series of hydrothermal diamond-anvil cell experiments at high temperature and pressure. These experiments will be complemented by the use of 1H/2H Nuclear Magnetic Resonance and TC/EA-Isotope Mass Ratio Spectrometry on quenched melts. Experimental results will help us constrain isotope exchange reactions as function of elemental speciation and partitioning between melts, crystalline phases and aqueous solutions. The novel use of vibrational spectroscopy for in-situ and real-time measurement of isotope molecules can be expanded to other applications including mineral physics, geochemistry and energy-related research. An undergraduate student will participate during a 10-week internship program established in the second and third year of the project. This research will also support the M.Sc. thesis of a graduate student from the George Mason University.