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Gregor Markl - One of the best experts on this subject based on the ideXlab platform.
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The effect of titanite and other HFSE-rich mineral (Ti-bearing Andradite, zircon, eudialyte) fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2020Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite-melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte-melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilímaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.20 page(s
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the effect of titanite and other hfse rich mineral ti bearing Andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2008Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:Abstract We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite–melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte–melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilimaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.
Ian M Coulson - One of the best experts on this subject based on the ideXlab platform.
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The effect of titanite and other HFSE-rich mineral (Ti-bearing Andradite, zircon, eudialyte) fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2020Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite-melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte-melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilímaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.20 page(s
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the effect of titanite and other hfse rich mineral ti bearing Andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2008Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:Abstract We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite–melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte–melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilimaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.
Roberto Dovesi - One of the best experts on this subject based on the ideXlab platform.
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elasticity of grossular Andradite solid solution an ab initio investigation
Physical Chemistry Chemical Physics, 2014Co-Authors: Valentina Lacivita, Philippe Darco, Roberto Dovesi, Alessandro ErbaAbstract:Grossular and Andradite are garnet end-members stable under upper mantle conditions. We perform ab initio simulations to investigate the dependence of the bulk modulus on chemical composition of the grossular–Andradite solid solution, Ca3Fe2−2xAl2x(SiO4)3. All-electron local basis sets of Gaussian-type orbitals and the hybrid B3LYP density functional are used. Our calculations predict a linear modulus-composition trend, in contrast to previous conjectures based on “heterogeneous” experimental measurements. We estimate the largest deviation from linearity to be about 0.5 GPa under ambient conditions, and to progressively reduce to less than 0.2 GPa at pressure P = 20 GPa. The bulk modulus is computed over the whole composition range 0 ≤ x ≤ 1 following two independent approaches: fitting energy–volume data to an equation-of-state and calculating elastic tensors. Results from the two methods are in perfect agreement, assuring consistency and high numerical accuracy of the adopted algorithms.
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anomalous birefringence in Andradite grossular solid solutions a quantum mechanical approach
Pacific Rim Conference on Multimedia, 2013Co-Authors: Valentina Lacivita, Philippe Darco, Roberto Orlando, Roberto Dovesi, Alessio MeyerAbstract:The static linear optical properties (refractive indices, birefringence and axial angle) of Andradite–grossular (Ca3Fe2Si3O12–Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn–Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1–8 Al for Fe atoms in the primitive cell of Andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the Andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.
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Anomalous birefringence in Andradite–grossular solid solutions: a quantum-mechanical approach
Physics and Chemistry of Minerals, 2013Co-Authors: Valentina Lacivita, Roberto Orlando, Roberto Dovesi, Philippe D’arco, Alessio MeyerAbstract:The static linear optical properties (refractive indices, birefringence and axial angle) of Andradite–grossular (Ca3Fe2Si3O12–Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn–Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1–8 Al for Fe atoms in the primitive cell of Andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the Andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.
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the infrared vibrational spectrum of Andradite grossular solid solutions a quantum mechanical simulation
American Mineralogist, 2013Co-Authors: Marco De La Pierre, Philippe Darco, Alessio Meyer, Yves Noel, Sami Mustapha, Roberto DovesiAbstract:Infrared spectroscopy is a powerful technique for the characterization of minerals, permitting insights into their structural and thermodynamic properties. The intrinsic complexity of mineral solid solutions makes the interpretation of their spectroscopic data a challenging task. In this work, the IR vibrational spectra of Andradite-grossular (Ca3Fe2Si3O12–Ca3Al2Si3O12) solid solutions were simulated at the ab initio level with the CRYSTAL09 code by using a large all-electron Gaussian-type basis set and the B3LYP hybrid functional. All the 23 symmetry-independent configurations resulting from the substitution of 1 to 8 Fe atoms with Al atoms in the 16 a octahedral site of the Andradite primitive cell were considered. The IR active transverse optical frequencies and their intensities were computed. Graphical representation of the spectra, animation of the modes and isotopic substitution of the cations were used as additional interpretation tools. The dominant high-frequency modes, corresponding to Si-O stretching motions, show a simple linear behavior of both frequencies and intensities with respect to the binary composition; this trend is related to the linear behavior of the mean lattice parameter. Also the frequencies of the low-energy bands show, roughly speaking, a linear dependence on composition; however, the behavior of the dominant intensities is more complicated and strongly connected to the Al and Fe atomic fraction. When considering different possible structures at fixed composition, some spectral features display a dependence upon short-range Y cation ordering. Overall, we show how ab initio calculations permit to analyze complex systems such as solid solutions, establishing relations among structure and properties and providing critical and robust interpretations to the experimental findings.
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magnetic interactions and electronic structure of uvarovite and Andradite garnets an ab initio all electron simulation with the crystal06 program
International Journal of Quantum Chemistry, 2010Co-Authors: Alessio Meyer, Fabien Pascale, Claudio M Zicovichwilson, Roberto DovesiAbstract:The ground-state electronic structure of a number of magnetic phases of the garnets Andradite (Ca3Fe2Si3O12) and uvarovite (Ca3Cr2Si3O12) has been investigated at the density functional theory level of approximation using the periodic ab initio code CRYSTAL. An all-electron Gaussian-type basis has been used in conjunction with the B3LYP hybrid functional. The exchange coupling constants between the first (J1a and J1b differentiating the two nonidentical sites), second (J2), and third (J3) nearest neighbors have been evaluated and are found to be in good agreement with the experimental data that is available for Andradite. As a consequence of both the different J1a to J1b ratio and the opposite sign of J2 in the two minerals, different antiferromagnetic (AF) ground states are found for uvarovite and Andradite, which is in agreement with experimental observation. Strong support for the additivity and transferability of the J constants is provided by calculations in which Cr and Fe ions are embedded in the related grossular structure. The mechanism for the stabilization of the AF states is discussed within the Anderson theory of superexchange; the kinetic energy gain in the AF states is calculated, and the spin density maps and profiles are examined. Density of states, charge density maps, and Mulliken population data complete the analysis of the electronic structure. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Philippe Darco - One of the best experts on this subject based on the ideXlab platform.
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elasticity of grossular Andradite solid solution an ab initio investigation
Physical Chemistry Chemical Physics, 2014Co-Authors: Valentina Lacivita, Philippe Darco, Roberto Dovesi, Alessandro ErbaAbstract:Grossular and Andradite are garnet end-members stable under upper mantle conditions. We perform ab initio simulations to investigate the dependence of the bulk modulus on chemical composition of the grossular–Andradite solid solution, Ca3Fe2−2xAl2x(SiO4)3. All-electron local basis sets of Gaussian-type orbitals and the hybrid B3LYP density functional are used. Our calculations predict a linear modulus-composition trend, in contrast to previous conjectures based on “heterogeneous” experimental measurements. We estimate the largest deviation from linearity to be about 0.5 GPa under ambient conditions, and to progressively reduce to less than 0.2 GPa at pressure P = 20 GPa. The bulk modulus is computed over the whole composition range 0 ≤ x ≤ 1 following two independent approaches: fitting energy–volume data to an equation-of-state and calculating elastic tensors. Results from the two methods are in perfect agreement, assuring consistency and high numerical accuracy of the adopted algorithms.
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anomalous birefringence in Andradite grossular solid solutions a quantum mechanical approach
Pacific Rim Conference on Multimedia, 2013Co-Authors: Valentina Lacivita, Philippe Darco, Roberto Orlando, Roberto Dovesi, Alessio MeyerAbstract:The static linear optical properties (refractive indices, birefringence and axial angle) of Andradite–grossular (Ca3Fe2Si3O12–Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn–Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1–8 Al for Fe atoms in the primitive cell of Andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the Andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.
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the infrared vibrational spectrum of Andradite grossular solid solutions a quantum mechanical simulation
American Mineralogist, 2013Co-Authors: Marco De La Pierre, Philippe Darco, Alessio Meyer, Yves Noel, Sami Mustapha, Roberto DovesiAbstract:Infrared spectroscopy is a powerful technique for the characterization of minerals, permitting insights into their structural and thermodynamic properties. The intrinsic complexity of mineral solid solutions makes the interpretation of their spectroscopic data a challenging task. In this work, the IR vibrational spectra of Andradite-grossular (Ca3Fe2Si3O12–Ca3Al2Si3O12) solid solutions were simulated at the ab initio level with the CRYSTAL09 code by using a large all-electron Gaussian-type basis set and the B3LYP hybrid functional. All the 23 symmetry-independent configurations resulting from the substitution of 1 to 8 Fe atoms with Al atoms in the 16 a octahedral site of the Andradite primitive cell were considered. The IR active transverse optical frequencies and their intensities were computed. Graphical representation of the spectra, animation of the modes and isotopic substitution of the cations were used as additional interpretation tools. The dominant high-frequency modes, corresponding to Si-O stretching motions, show a simple linear behavior of both frequencies and intensities with respect to the binary composition; this trend is related to the linear behavior of the mean lattice parameter. Also the frequencies of the low-energy bands show, roughly speaking, a linear dependence on composition; however, the behavior of the dominant intensities is more complicated and strongly connected to the Al and Fe atomic fraction. When considering different possible structures at fixed composition, some spectral features display a dependence upon short-range Y cation ordering. Overall, we show how ab initio calculations permit to analyze complex systems such as solid solutions, establishing relations among structure and properties and providing critical and robust interpretations to the experimental findings.
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Andradite uvarovite solid solutions an ab initio all electtron quantum mechanical simulation with the crystal code
Journal of Physical Chemistry C, 2009Co-Authors: Alessio Meyer, Philippe Darco, Roberto Orlando, Roberto DovesiAbstract:Andradite−uvarovite (Ca3Fe2Si3O12−Ca3Cr2Si3O12) solid solutions have been investigated at an ab initio quantum-mechanical level by using an all-electron Gaussian-type basis set and the hybrid B3LYP functional in its unrestricted formulation. Only ferromagnetic phases have been considered. All possible nonequivalent geometrical configurations resulting from the substitution of Cr atoms for x = 1−8 Fe atoms in the 16a site in the garnet primitive cell have been fully optimized (cell parameters and fractional coordinates of 80 atoms). As the lattice parameters of the two end-members are very similar (11.99 and 12.05 A for uvarovite and Andradite, respectively), geometry rearrangements at the various x are extremely small, the largest excess volume being 0.15 A3 and the largest excess energy 3.68 kJ/mol. Thermodynamic functions are calculated from the configurational contribution to entropy and disregarding the vibrational contribution, which is expected to be negligible. Almost ideal miscibility is predicted.
Michael A W Marks - One of the best experts on this subject based on the ideXlab platform.
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The effect of titanite and other HFSE-rich mineral (Ti-bearing Andradite, zircon, eudialyte) fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2020Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite-melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte-melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilímaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.20 page(s
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the effect of titanite and other hfse rich mineral ti bearing Andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts
Chemical Geology, 2008Co-Authors: Michael A W Marks, Ian M Coulson, Julian Schilling, Dorrit E Jacob, Axel K Schmitt, Gregor MarklAbstract:Abstract We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing Andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite–melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite. Zircon, eudialyte and Ti-bearing Andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte–melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilimaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.
