HR: 0800h
AN: V41A-1433    [Abstracts]
TI: Thermophysical Properties of Fluids Under Mantle Conditions of Pressure and Temperature
AU: Abramson, E H
EM: evan@ess.washington.edu
AF: Dept. of Earth and Space Sciences, University of Washington, Seattle, WA 98195 United States
AU: * Brown, J M
EM: brown@ess.washington.edu
AF: Dept. of Earth and Space Sciences, University of Washington, Seattle, WA 98195 United States
AB: The thermophysical properties of volatile phases (including equations of state, viscosity, and thermal diffusivity) enter into determinations of phase equilibria and in the modeling of dynamic processes and chemical kinetics. The acquisition of accurate data in a mantle regime of pressure and temperature has only recently been possible. In comparing our high pressure and high temperature experimental results for H₂O and CO_2 with predictions of existing equations-of-state (that often require extrapolation to a mantle regime of pressure and temperature) we find that the latter are often in significant error. In part, a problem is the use of mathematical forms chosen for their limited number of parameters. Typically, these equations of state do not extrapolate well in pressure and temperature, or do not yield correct results when used to estimate thermodynamic parameters other than those to which they were originally fitted. A parameterization, based on a well-considered expansion of the Helmholtz free energy, has the ability to fit data within their uncertainties while still exhibiting good results in extrapolation and in the prediction of other thermodynamic variables. Similarly, we find that new data on thermal diffusivities and viscosities better guide the choice of methods of representation and extrapolation over large changes in temperature, pressure and density.
DE: 3919 Equations of state
DE: 3939 Physical thermodynamics
DE: 8411 Thermodynamics (0766, 1011, 3611)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005