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.
