TY - JOUR
T1 - The activity-composition relationship of oxygen and hydrogen isotopes in aqueous salt solutions
T2 - III. Vapor-liquid water equilibration of NaCl solutions to 350°C
AU - Horita, Juske
AU - Cole, David R.
AU - Wesolowski, David J.
N1 - Funding Information:
Acknowledgments-Thanks are due to R. W. Carter, J. P. Jensen, and D. A. Palmer for making possible the high-temperature liquid-vapor experiments. K. Kazahaya and T. Dtiesner provided us with their preliminary, unpublished data. Reviews by C. M. Graham and S. R. Poulson were helpful. This study was supported by the Geoscience Program of the Office of Basic Energy Sciences and the Geothermal Technology Program of the Office of Energy Efficiency and Renewable Energy, US Department of Energy, under contract number DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.
PY - 1995/3
Y1 - 1995/3
N2 - The effect of dissolved NaCl on equilibrium oxygen and hydrogen isotope fractionation factors between liquid water and water vapor was precisely determined in the temperature range from 130-350°C, using two different types of apparatus with static or dynamic sampling techniques of the vapor phase. The magnitude of the oxygen and hydrogen isotope effects of NaCl is proportional to the molality of liquid NaCl solutions at a given temperature. Dissolved NaCl lowers appreciably the hydrogen isotope fractionation factor between liquid water and water vapor over the entire temperature range. NaCl has little effect on the oxygen isotope fractionation factor at temperatures below about 200°C, with the magnitude of the salt effect gradually increasing from 200-350°C. Our results are at notable variance with those of Truesdell (1974) and Kazahaya (1986), who reported large oxygen and hydrogen isotope effects of NaCl with very complex dependencies on temperature and NaCl molality. Our high-temperature results have been regressed along with our previous results between 50 and 100°C (Horita et al., 1993a) and the low-temperature literature data to simple equations which are valid for NaCl solutions from 0 to at least 5 molal NaCl in the temperature range from 10-350°C. Our preliminary results of oxygen isotope fractionation in the system CaCO3-water ± NaCl at 300°C and 1 kbar are consistent with those obtained from the liquid-vapor equilibration experiments, suggesting that the isotope salt effects are common to systems involving brines and any other coexisting phases or species (gases, minerals, dissolved species, etc.). The observed NaCl isotope effects at elevated temperatures should be taken into account in the interpretation of isotopic data of brine-dominated natural systems.
AB - The effect of dissolved NaCl on equilibrium oxygen and hydrogen isotope fractionation factors between liquid water and water vapor was precisely determined in the temperature range from 130-350°C, using two different types of apparatus with static or dynamic sampling techniques of the vapor phase. The magnitude of the oxygen and hydrogen isotope effects of NaCl is proportional to the molality of liquid NaCl solutions at a given temperature. Dissolved NaCl lowers appreciably the hydrogen isotope fractionation factor between liquid water and water vapor over the entire temperature range. NaCl has little effect on the oxygen isotope fractionation factor at temperatures below about 200°C, with the magnitude of the salt effect gradually increasing from 200-350°C. Our results are at notable variance with those of Truesdell (1974) and Kazahaya (1986), who reported large oxygen and hydrogen isotope effects of NaCl with very complex dependencies on temperature and NaCl molality. Our high-temperature results have been regressed along with our previous results between 50 and 100°C (Horita et al., 1993a) and the low-temperature literature data to simple equations which are valid for NaCl solutions from 0 to at least 5 molal NaCl in the temperature range from 10-350°C. Our preliminary results of oxygen isotope fractionation in the system CaCO3-water ± NaCl at 300°C and 1 kbar are consistent with those obtained from the liquid-vapor equilibration experiments, suggesting that the isotope salt effects are common to systems involving brines and any other coexisting phases or species (gases, minerals, dissolved species, etc.). The observed NaCl isotope effects at elevated temperatures should be taken into account in the interpretation of isotopic data of brine-dominated natural systems.
UR - http://www.scopus.com/inward/record.url?scp=0028844884&partnerID=8YFLogxK
U2 - 10.1016/0016-7037(95)00031-T
DO - 10.1016/0016-7037(95)00031-T
M3 - Article
AN - SCOPUS:0028844884
SN - 0016-7037
VL - 59
SP - 1139
EP - 1151
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 6
ER -