2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 1
Presentation Time: 1:30 PM-5:30 PM


LABOTKA, Theodore C.1, ANOVITZ, Lawrence M.1 and BLENCOE, James G.2, (1)Department of Earth and Planetary Sciences, Univ of Tennessee, Knoxville, TN 37996, (2)Oak Ridge National Lab, P.O. Box 2008, Bldg. 4500-S, Oak Ridge, TN 37831-6110, tlabotka@utk.edu

Experiments in the system H2O–CO2–NaCl at 500 °C, 50 MPa, have delimited the solubility of halite in H2O–CO2 fluids and have determined the tie lines between fluid and halite at constant values of aH2O. The phase diagram shows a one-phase vapor field, a one-phase brine field, two-phase vapor + halite, vapor + brine, and brine + halite fields, and a three-phase vapor + brine + halite field. The halite-saturated vapor ranges in composition from xNaCl ≈ 0 in CO2 to 0.08 at the vapor corner of the three-phase field, where xH2O ≈ 0.6. The aH2O was fixed during the experiment, and the aNaCl in the vapor was fixed by saturation with halite. The aCO2 was determined by integrating the Gibbs–Duhem equation along the saturation curve, ∑xid lnai=0. The effect of adding NaCl to H2O–CO2 vapor is represented by values of ∂ln(γH2O)/∂xNaCl ranging from −7 in CO2-rich vapor to 3 in H2O-rich vapor. The value of ∂ln(γCO2)/∂xNaCl shows an even larger range from 10 to −18 over the same compositional range. The measured values of the activities in the three-component system are combined with models for the activities in the H2O–CO2 and H2O–NaCl binaries to calculate the complete phase diagram.