Accomplishment Based Renewal: Experimental Studies of the PTX Properties of Immiscible Fluids at Crustal PT Conditions

知识价值：H2O-CO2-NaCl-KCl- CaCl2体系近似流体的不混相（沸腾）在许多地壳环境中是常见的，包括浅成热液贵金属矿床、斑岩型铜金钼矿床、变质矿脉金矿床和其他地壳火成岩和变质环境。流体不混相是一种将某些元素划分和富集到两个共存相中的有效机制，因此在地壳地球化学过程中起着重要作用。流体包裹体为这些环境中流体不混溶的发生提供了最好的证据，但由于缺乏在地壳压力-温度（P-T）条件下共存流体组成的实验PTX数据，我们从天然包裹体中解释微量温度和微量分析数据的能力受到限制。实验将采用合成流体包裹体技术，确定H2O-CO2-NaCl、H2O-NaCl-KCl和H2O-NaCl-CaCl2三元体系中共存流体的组成。不混相的P-T极限将根据在已知条件下捕获的合成流体包裹体的观察来确定。在单相流体场中包裹体均表现出相同的室温相关系和显微测温行为。那些被困在两相场中的物质表现出相行为的双峰分布，表明液相和气相在高温高压下存在。共存的液相和气相的组成将通过显微测温分析确定，使用先前确定的适当流体系统的数据进行解释，并辅以拉曼光谱来识别子矿物，并确定含二氧化碳包裹体的H2O/CO2比。拟议的研究是正在进行的实验工作的延续，旨在提供与地质有关的流体的基本PVTX数据，以便我们可以更好地了解流体在地壳和上地幔的地球化学和流变演化中发挥的关键作用。更广泛的影响：这项资助将为研究生提供培训，帮助他们为成功的地球科学事业做好准备。该项目还将每年支持一名或多名本科生提供有意义的研究经验。更广泛的影响还包括PI为世界各地的学生和专业人士提供关于地球流体的讲座和研讨会，以及为弗吉尼亚理工大学的非科学专业学生教授地球科学入门课程。这些活动反映了PI研究的更广泛影响以及优质本科教育在发展科学素养社会中的重要作用。

Intellectual merit: Immiscibility (boiling) in fluids approximated by the H2O-CO2-NaCl-KCl- CaCl2 system is common in many crustal environments, including epithermal precious metals deposits, porphyry copper-gold-molybdenum deposits, metamorphic lode gold deposits and other crustal igneous and metamorphic environments. Fluid immiscibility is an effective mechanism for partitioning and concentrating certain elements into one or the other of the two coexisting phases and thus plays an important role in crustal geochemical processes. Fluid inclusions provide the best evidence for the occurrence of fluid immiscibility in these environments, but our ability to interpret microthermometric and microanalytical data from natural inclusions is limited by the lack of experimental PTX data on compositions of coexisting fluids at crustal pressure-temperature (P-T) conditions. Experiments will be conducted using the synthetic fluid inclusion technique to determine compositions of coexisting fluids in the H2O-CO2-NaCl, H2O-NaCl-KCl and H2O-NaCl-CaCl2 ternary subsystems. The P-T limits of immiscibility will be defined based on observations of synthetic fluid inclusions trapped at known conditions. Fluid inclusions trapped in the one-phase fluid field all show identical room temperature phase relations and microthermometric behavior. Those trapped in the two-phase field show a bimodal distribution of phase behavior, indicative of the liquid and vapor phases that were present at elevated temperature and pressure. Compositions of the coexisting liquid and vapor phases will be determined from microthermometric analyses, interpreted using previously determined data for the appropriate fluid system, and supplemented by Raman spectroscopy to identify daughter minerals and to determine the H2O/CO2 ratio of CO2-bearing inclusions. The proposed research represents a continuation of ongoing experimental efforts designed to provide fundamental PVTX data on geologically-relevant fluids so that we may better understand the critical role that fluids play in the geochemical and rheological evolution of the crust and upper mantle. Broader impact: Funding provided by this grant will provide training for graduate students and help prepare them for successful careers in the earth sciences. This project will also support one or more undergraduate students each year to provide a meaningful research experience. The broader impacts also include lectures and workshops on Fluids in the Earth that the PI offers to students and professionals worldwide, as well as teaching introductory earth sciences courses to non-science majors at Virginia Tech. These activities reflect the broader impacts of the PI's research and the important role that quality undergraduate education plays in developing a scientifically literate society.