HR: 0800h
AN: V41A-1358    [Abstracts]
TI: The Melting Curve of Carbon Dioxide and Implications for the Fluid Equation-of-State
AU: * Abramson, E H
EM: evan@ess.washington.edu
AF: Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310 United States
AU: Brown, J M
EM: brown@ess.washington.edu
AF: Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310 United States
AB: Despite being a dominant volatile in magma, the thermodynamic properties of carbon dioxide remain problematic from mid-crustal to mantle conditions of pressure and temperature. Several published equations of state are neither in agreement nor do they always match existing high-pressure data. In order to investigate the properties of fluid carbon dioxide, the melting curve of supercritical carbon dioxide has been measured up to 5.5 GPa. When coupled with a robust thermodynamic model for solid carbon dioxide, these data allow a test of various proposed equations-of-state for the fluid. In order to match the melting curve, both the densities predicted by the Pitzer and Sterner (1994) equation-of-state and those predicted by Span and Wagner (1996) must be decreased by a few percent. This finding is in accord with shock data at higher pressures ($>$10 GPa) which also suggest the necessity of lower fluid densities. The equation-of-state of Frost and Wood (1997), based on measurements of graphite/CO2 equilibria, gives substantially higher densities and is inconsistent with the shock data. Along the cooler geotherms associated with older slabs the solid phase of carbon dioxide is stable into the lower mantle.
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3939 Physical thermodynamics
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting