Abstract
The volume of lawsonite, CaAl2Si2O7(OH)2 · H2O, has been measured up to 7 GPa and 873 K using in situ energy dispersive powder diffraction and a multi-anvil high pressure-temperature cell at the Synchrotron Radiation Source, Daresbury Laboratory, U.K. Measurements were made on isotherms at 298, 323, 373, 473, 573, 673, 773, and 873 K within the pressure range. Sample pressure was measured from a NaCl standard mixed with the sample; the unit-cell volume of lawsonite was taken from the same diffraction pattern. The data gave an ambient temperature isothermal bulk modulus of K298 112 ± 6 GPa, similar to previous values. This value overestimates the temperature stability of lawsonite in thermodynamic calculations. A fit of the Birch-Murnaghan equation of state to the whole high pressure and temperature data set gave an isothermal bulk modulus of K298 = 125 ±5 GPa and a dK/dT of -0.01 ± 0.01/K, with K1 set to a value of 4 and the expansivity set to 3.16 × 10-5/K. Using these values to calculate the pressure-temperature positions of three of lawsonite’s dehydration reactions improved the agreement between observed and calculated positions of the lawsonite dehydration reactions to within experimental and calculation error. This work shows that the ambient temperature bulk modulus and ambient pressure expansivity do not adequately describe the volume behavior of lawsonite at combined high pressure and temperature.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Application of new experimental and garnet Margules data to the garnet-biotite geothermometer
- Volumes of mixing in aluminosilicate garnets: Solid solution and strain behavior
- Cerium anomaly and Th/U fractionation in the 1.85 Ga Flin Flon Paleosol: Clues from REE- and U-rich accessory minerals and implications for paleoatmospheric reconstruction
- Os solubility in silicate melts: New efforts and results
- Enstatite-forsterite-water equilibria at elevated temperatures and pressures
- The OH-F substitution in synthetic pargasite at 1.5 kbar, 850 °C
- Uptake of aqueous Pb by Cl-, F–, and OH– apatites: Mineralogic evidence for nucleation mechanisms
- Temperature dependence of the hyperfine parameters of synthetic P21/c Mg-Fe clinopyroxenes along the MgSiO3-FeSiO3 join
- Single-crystal thermometric calibration of Fe-Mg order-disorder in pigeonites
- TEM observations on the P1̄ -I1̄ phase transition in feldspars along the join CaAl2Si2O8-SrAl2Si2O8
- Phase transitions induced by solid solution in stuffed derivatives of quartz: A powder synchrotron XRD study of the LiAlSiO4-SiO2 join
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- Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel’s salt)
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- Rietveld analysis of dicalcium aluminate (Ca2Al2O5) – A new high pressure phase with the Brownmillerite-type structure
- Suredaite, PbSnS3, a new mineral species, from the Pirquitas Ag-Sn deposit, NW-Argentina: mineralogy and crystal structure
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