Experimental and Modeling Studies of the PVTX and Phase Equilibrium Properties of Crustal Fluids

地球上的自然流体影响许多过程，包括贵重金属矿石的形成、石油的产生和积聚、火山爆发的爆炸性，并可能引发大地震。这些流体的组成因其发生的环境而有很大的不同。分析地球深处自然流体的能力的最新进展表明，在许多环境中的流体中，含有大量铁的盐是常见的。为了充分认识和理解含铁流体在各种地质过程中所起的重要作用，有必要在代表这些流体发生的不同地质环境的温度、压力和成分范围内，对流体的物理和化学性质有很好的了解。这些信息反过来又帮助地质学家更好地勘探现代社会所需的有价值的金属和能源资源，并帮助火山学家和地震学家更好地评估与火山爆发和地震有关的风险。该项目代表了一项实验研究，旨在确定在适合地壳岩浆热液系统的一系列压力和温度条件下，H2O-NaCl-CaCl2-FeCl2和H2O-NaCl-KCl-FeCl2系统中流体的相平衡、体积和热力学性质，并建立数值模型来解释从天然流体包裹体中获得的微测温数据。这个项目代表了一个合乎逻辑的下一步，即提高我们理解日益复杂的流体的能力，这些流体代表着天然存在的流体。具体来说，这项工作将确定两相场的位置（即不混相的极限）作为压力、温度和流体成分（PTX）的函数，以及两相（液体+蒸汽）场中共存相的成分。还将确定临界点的位置和沿临界等等值线的P-T点轨迹，单相流体场的等等值线，以及基于流体包裹体显微测温法解释流体成分所需的低温相平衡。这些新数据将极大地促进目前对地壳岩浆热液系统的认识，并为估计高温高压下复杂含水流体的热力学性质提供基础实验数据。

Natural fluids that occur in the Earth affect many processes, including the formation of valuable ores of metals, the generation and accumulation of petroleum, the explosivity of volcanic eruptions, and can trigger large earthquakes. The compositions of these fluids vary widely depending on the environment in which they occur. Recent advances in the ability to analyze natural fluids from deep in the earth have shown that salts containing significant amounts of iron are common in fluids from many environments. In order to fully appreciate and understand the important role that iron-bearing fluids play in various geological processes, it is necessary to have a good understanding of the physical and chemical properties of the fluids over the range of temperatures, pressures and compositions representative of the different geological environments in which these fluids occur. This information, in turn, helps geologists to better explore for valuable metallic and energy resources required by modern society, and helps volcanologists and seismologists to better assess risks associated with volcanic eruptions and earthquakes.This project represents an experimental study to determine the phase equilibrium, volumetric and thermodynamic properties of fluids in the systems H2O-NaCl-CaCl2-FeCl2 and H2O-NaCl-KCl-FeCl2 over a range of pressure and temperature conditions appropriate to crustal magmatichydrothermal systems, and to develop numerical models to interpret microthermometric data obtained from natural fluid inclusions. This project represents a logical next step in improving our ability to understand increasingly more complex fluids that are representative of naturally occurring fluids. Specifically, this work will determine the location of the two-fluid phase field (i.e., limits of immiscibility) as a function of pressure, temperature and fluid composition (PTX), as well as the compositions of coexisting phases in the two-phase (liquid + vapor) field. The location of the critical point and the locus of P-T points along the critical isochore, isochores in the one-phase fluid fields, and low temperature phase equilibria required to interpret fluid compositions based on fluid inclusion microthermometry will also be determined. These new data will significantly advance current understanding of crustal magmatic hydrothermal systems and provide basic experimental data that may be used to estimate thermodynamic properties of complex aqueous fluids at elevated temperatures and pressures.