Phase Relations Between Silicate Melts and Crustal Brines

拟议研究的最终目标是了解含盐地壳流体在地球更深的地壳和上地幔的熔融过程和物质运输中的作用。所提出的实验将加强目前对俯冲带岩浆作用的了解，并衡量咸水流体对地壳浅层环境中花岗岩形成熔体稳定性的贡献。拟议的研究将促进对与地球深层水循环有关的质量和热传递的了解，在水循环中，水在俯冲带进入地幔，然后在火山释放回地表。理解C-O-H挥发物在类地行星内部的引入、运输和储存与宜居的性质、生命的起源以及有利于生命的外部条件的证据有着深刻的联系。硅酸盐熔体的结构特征及其玻璃形成能力直接关系到材料和玻璃科学。实验数据将通过实验阶段关系图书馆和机构网络基础设施内的数据储存库向公众提供。乔治梅森大学(GMU)的本科生/研究生将参加一系列讲座和实验室演示/参观，GMU的一些本科生将在为期10周的暑期实习计划中参与该项目，这将在一个研究机构(CIW)和一所公立公立大学(GMU)之间建立牢固的合作伙伴关系。挥发物在硅酸盐熔体和水流体中的溶解和溶解机制控制着地幔通量，并影响共存相的性质，如扩散率、导电性和粘度。这对沿大洋中脊、陆壳浅层和俯冲带发育的岩浆系统之间的物理和化学不均一性产生了深远的影响。然而，人们对硅酸盐熔体-流体相关系知之甚少，尤其是对富含溶解的碱、碱土和卤素离子的盐类流体。该方案旨在探讨溶解盐、流体pH和熔体过碱度对硅酸盐熔体与地壳卤水之间的相关系的影响，以更好地了解熔体聚合和C-O-H在共存相中的溶解度。该项目将限制熔体-流体关系不仅是压力/温度的函数，而且还是共存相的相对丰度和成分变异性的函数。在一系列水热金刚石砧座实验中，拉曼振动/红外光谱将被用来原位和实时地研究与富电解质水溶液共存的硅酸盐熔体的结构、挥发成分和性质。实验将揭示二氧化碳的溶解度、网络修饰阳离子和熔融聚合程度之间的相互作用。现场研究将由在高温和高压下从熔体-流体平衡中冷却的玻璃中的大量二氧化碳溶解度测量来补充。这项工作的核心是创新地整合了非现场和现场实验方案以及实时化学和光谱分析。在这项研究中，使用超纯人造钻石砧座将极大地提高监测原位熔体-流体相互作用的分析方法的有效性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The ultimate objective of the proposed study is to understand the role of saline crustal fluids on melting processes and material transport in Earth's deeper crust and upper mantle. Experiments proposed will enhance the current understanding of magmatic processes in subduction zones and gauge the contribution of saline fluids on the stability of granitic-forming melts at shallow crustal environments. The proposed study will promote understanding on the mass and heat transfer associated with the deep Earth's hydrological cycle, wherein water is carried into the mantle at subduction zones and released back to the surface at volcanoes. Understanding the introduction, transport, and storage of C-O-H volatiles in the interiors of terrestrial-like planets is profoundly linked to the nature of habitability, the origin of life, and the external evidence of conditions favorable for life. Structural characterization of silicate melts and their glass-forming abilities are directly relevant to materials and glass science. Experimental data will be made available to the public through the Library of Experimental Phase Relations, and a data repository hosted within the institution's web infrastructure. A series of lectures and lab demonstrations/tours will be delivered to George Mason University (GMU) undergraduate/graduate students, and some undergraduate students from GMU will participate in the project during a 10-week summer internship program, creating a strong partnership between a research-institution (CIW) and a public state-funded University (GMU).The solubility and solution mechanisms of volatiles in silicate melts and aqueous fluids governs mantle fluxes, and affects the properties of coexisting phases such as diffusivity, electrical conductivity and viscosity. This has a profound effect on the physical and chemical heterogeneities between the magmatic systems developed along mid-ocean ridges, shallow continental crust and subduction zones. Very little is known, however, about the silicate melt-fluid phase relations, especially for saline fluids enriched in dissolved alkalis, alkaline earths, and halogen ions. This proposal aims to explore the effect of dissolved salts, fluid pH and melt peralkalinity on the phase relations between silicate melts and crustal brines to better understand melt polymerization and C-O-H solubility in the coexisting phases. This project will constrain the melt-fluid relationships as function not only of pressure/temperature but also of relative abundances and compositional variability of the coexisting phases. In a series of hydrothermal diamond anvil cell experiments, Raman vibrational/Infrared spectroscopy will be employed for the in-situ and real-time investigation of the structure, volatile composition and properties of silicate melts coexisting with electrolyte-enriched aqueous solutions. Experiments will reveal the interplay between CO2 solubility, network-modifying cations and extent of melt polymerization. The in-situ studies will be complimented by bulk CO2 solubility measurements in glasses quenched from melt-fluid equilibria at high temperatures and pressures. At the core of this effort is an innovative integration of ex-situ and in-situ experimental protocols along with real-time chemical and spectroscopic analysis. In this study, use of ultrapure synthetic diamond anvils will increase tremendously the effectiveness of analytical methods that monitor in-situ melt-fluid interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.