Article
Licensed
Unlicensed
Requires Authentication
Cation disorder in dolomite, CaMg(CO3)2, and its influence on the aragonite + magnesite ↔ dolomite reaction boundary
-
Sytle M. Antao
,
Willem H. Mulder
Published/Copyright:
March 28, 2015
Abstract
The structure of dolomite, CaMg(CO3)2, was determined from 298 to 1466 K at a constant pressure of about 3 GPa using in situ synchrotron X-ray diffraction data to investigate the state of disorder. An order parameter s, defined as 2 xCa - 1, varies from s = 1 (where xCa = 1) for a completely ordered dolomite to s = 0 (where xCa = 0.5) for a completely disordered dolomite. On heating, there is no measured change in s until the temperature is high enough to cause exchange of Ca2+ and Mg2+ cations. Significant disorder began to occur at about 1234 K [s = 0.83(1)] and increases along a smooth pathway to T = 1466 K [s = 0.12(5)]. The R3 - ↔ R3 - c transition in dolomite is described by a modified Bragg-Williams thermodynamic model with the following molar free energy of disorder, G̅d (T; s) = RTc[1 - s2 + 1/2 a(s4 - 1) - (T/Tc) {2 ln2 - (1+s) ln(1 + s) - (1 - s) ln(1 - s)}]. Using Tc = 1466 K and a = -0.29, this model provides an excellent agreement with experimental data. Moreover, the maximum enthalpy of disorder, H̅d(s = 0) = RTc(1 - 1/2 a) ~ 14 kJ/mol, agrees with published calorimetric data. A thermodynamic description of the aragonite + magnesite ↔ dolomite reaction boundary is also presented and it reproduces the main qualitative features correctly.
Received: 2004-2-10
Accepted: 2004-3-22
Published Online: 2015-3-28
Published in Print: 2004-7-1
© 2015 by Walter de Gruyter Berlin/Boston
You are currently not able to access this content.
You are currently not able to access this content.
Articles in the same Issue
- Hydroxyl in omphacites and omphacitic clinopyroxenes of upper mantle to lower crustal origin beneath the Siberian platform
- Structural variations induced by difference of the inert pair effect in the stibnite-bismuthinite solid solution series (Sb,Bi)2S3
- Hydrogen solubility and speciation in natural, gem-quality chromian diopside
- Ultrastructure, aggregation-state, and crystal growth of biogenic nanocrystalline sphalerite and wurtzite
- Impactite from Henbury, Australia
- Neutron and synchrotron X-ray diffraction study of the structures and dehydration behaviors of ramsdellite and “groutellite”
- Hydrothermal synthesis and crystal chemistry of the new strontium uranyl selenites, Sr[(UO2)3(SeO3)2O2]⋅4H2O and Sr[UO2(SeO3)2]
- Study of cation order-disorder in MgAl2O4spinel by in situ neutron diffraction up to 1600 K and 3.2 GPa
- Magnetic granulometry from equilibrium magnetization measurements: Mineral magnetometry of superparamagnetic particles and application to synthetic ferrihydrites
- Hydroxide in kyanite: A quantitative determination of the absolute amount and calibration of the IR spectrum
- Analysis of uranyl-bearing phases by EXAFS spectroscopy: Interferences, multiple scattering, accuracy of structural parameters, and spectral differences
- X-ray diffraction evidence for a monoclinic form of stibnite, Sb2S3, below 290 K
- Sulfur species at chalcopyrite (CuFeS2) fracture surfaces
- Dehydration and rehydration process in boggsite: An in situ X-ray single-crystal study
- Empressite, AgTe, from the Empress-Josephine mine, Colorado, U.S.A.: Composition, physical properties, and determination of the crystal structure
- Correlation of pH-dependent surface interaction forces to amino acid adsorption: Implications for the origin of life
- A near-infrared spectroscopic study of hydroxyl in natural chondrodite
- High-pressure elasticity of a natural magnetite crystal
- Isotopic and chemical alteration of zircon by metamorphic fluids: U-Pb age depth-profiling of zircon crystals from Barrowʼs garnet zone, northeast Scotland
- A novel approach to determine high-pressure high-temperature fluid and melt compositions using diamond-trap experiments
- Lindbergite, a new Mn oxalate dihydrate from Boca Rica mine, Galiléia, Minas Gerais, Brazil, and other occurrences
- Pyrophyllite dehydroxylation process by First Principles calculations
- Plagioclase from planetary basalts: Chemical signatures that reflect planetary volatile budgets, oxygen fugacity, and styles of igneous differentiation
- The structure of the manganese oxide on the sheath of the bacterium Leptothrix discophora: An XAFS study
- An X-ray Rietveld study of piemontite on the join Ca2Al3Si3O12(OH)–Ca2Mn33+Si3O12(OH) formed by hydrothermal synthesis
- Raman spectroscopy of basic copper(II) and some complex copper(II) sulfate minerals: Implications for hydrogen bonding
- Incorporation of sodium into the chlorite structure: the crystal structure of glagolevite, Na(Mg,Al)6[Si3AlO10](OH,O)8
- Cation disorder in dolomite, CaMg(CO3)2, and its influence on the aragonite + magnesite ↔ dolomite reaction boundary
Articles in the same Issue
- Hydroxyl in omphacites and omphacitic clinopyroxenes of upper mantle to lower crustal origin beneath the Siberian platform
- Structural variations induced by difference of the inert pair effect in the stibnite-bismuthinite solid solution series (Sb,Bi)2S3
- Hydrogen solubility and speciation in natural, gem-quality chromian diopside
- Ultrastructure, aggregation-state, and crystal growth of biogenic nanocrystalline sphalerite and wurtzite
- Impactite from Henbury, Australia
- Neutron and synchrotron X-ray diffraction study of the structures and dehydration behaviors of ramsdellite and “groutellite”
- Hydrothermal synthesis and crystal chemistry of the new strontium uranyl selenites, Sr[(UO2)3(SeO3)2O2]⋅4H2O and Sr[UO2(SeO3)2]
- Study of cation order-disorder in MgAl2O4spinel by in situ neutron diffraction up to 1600 K and 3.2 GPa
- Magnetic granulometry from equilibrium magnetization measurements: Mineral magnetometry of superparamagnetic particles and application to synthetic ferrihydrites
- Hydroxide in kyanite: A quantitative determination of the absolute amount and calibration of the IR spectrum
- Analysis of uranyl-bearing phases by EXAFS spectroscopy: Interferences, multiple scattering, accuracy of structural parameters, and spectral differences
- X-ray diffraction evidence for a monoclinic form of stibnite, Sb2S3, below 290 K
- Sulfur species at chalcopyrite (CuFeS2) fracture surfaces
- Dehydration and rehydration process in boggsite: An in situ X-ray single-crystal study
- Empressite, AgTe, from the Empress-Josephine mine, Colorado, U.S.A.: Composition, physical properties, and determination of the crystal structure
- Correlation of pH-dependent surface interaction forces to amino acid adsorption: Implications for the origin of life
- A near-infrared spectroscopic study of hydroxyl in natural chondrodite
- High-pressure elasticity of a natural magnetite crystal
- Isotopic and chemical alteration of zircon by metamorphic fluids: U-Pb age depth-profiling of zircon crystals from Barrowʼs garnet zone, northeast Scotland
- A novel approach to determine high-pressure high-temperature fluid and melt compositions using diamond-trap experiments
- Lindbergite, a new Mn oxalate dihydrate from Boca Rica mine, Galiléia, Minas Gerais, Brazil, and other occurrences
- Pyrophyllite dehydroxylation process by First Principles calculations
- Plagioclase from planetary basalts: Chemical signatures that reflect planetary volatile budgets, oxygen fugacity, and styles of igneous differentiation
- The structure of the manganese oxide on the sheath of the bacterium Leptothrix discophora: An XAFS study
- An X-ray Rietveld study of piemontite on the join Ca2Al3Si3O12(OH)–Ca2Mn33+Si3O12(OH) formed by hydrothermal synthesis
- Raman spectroscopy of basic copper(II) and some complex copper(II) sulfate minerals: Implications for hydrogen bonding
- Incorporation of sodium into the chlorite structure: the crystal structure of glagolevite, Na(Mg,Al)6[Si3AlO10](OH,O)8
- Cation disorder in dolomite, CaMg(CO3)2, and its influence on the aragonite + magnesite ↔ dolomite reaction boundary
