9725248 Bodnar The objective of the proposed research is to develop the hydrothermal diamond anvil cell (HDAC) for use as a pressurized fluid inclusion stage. The HDAC will then be used in conjunction with the synthetic fluid inclusion technique to obtain PVTX data for geologically-important system H2O-CO2 NaCl at temperatures and pressures beyond the range accessible with conventional experimental techniques normally used to determine PVTX properties of fluids. Results of a pilot study document the feasibility of using the HDAC as a pressurized fluid inclusion stage to prevent non-elastic volume changes for such inclusion by heating the gas salt-bearing inclusions under a high hydrostatic confining pressure in the HDAC. In this study, the HDAC will be used as a pressurized fluid inclusion stage to determine the P-T location of the H2O-CO2solvus and the slopes of isochores at pressures up to approximately 7-9 kbar. The research will also result in the development of a protocol for the most efficient use of the HDAC as a pressurized fluid inclusion stage for the study of natural fluid inclusions that currently cannot be studied in the conventional one-atmosphere heating stage.