An equation of state (P-V-T relation) for magmatic liquids is critical for quantitative models of partial melting and melt transport beneath spreading ridges and subduction zones, where oceanic and continental crust are formed. A major challenge to thermodynamic models of partial melting in the deep mantle is the lack of information on the density of magmatic liquids at high pressure. The largest uncertainties are with the pressure dependence to melt compressibility and with how volatile components affect melt density at high pressure. The primary objective of this proposal is to measure the compressibility and density of numerous geologically relevant liquids as a systematic function of pressure and temperature, using a frequency-sweep acoustic interferometer in an internally heated pressure. These data will provide a quantitative link between the microscopic structure of liquids, obtained from spectroscopic studies, and their macroscopic properties. Thus these data will greatly enhance the utility and insights provided by different spectroscopic tools and molecular modeling within the earth and material sciences. The sound velocity data on melts at high pressure will also be helpful for improved interpretation of seismic velocity variations in the crust and mantle, where partial melt may be present. Graduate students will be partially supported by this grant. The interdisciplinary nature of the training that they will receive is excellent preparation for either an academic career in the earth sciences or an industry career involving high-tech materials.
