The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Veronika Homolova - One of the best experts on this subject based on the ideXlab platform.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:Abstract We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D < 0.2). Partition coefficients for Ir, Ru and Rh measured at more oxidizing conditions in this and previous studies are 10 to 1000 times higher than results from experiments using graphite capsules. We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
James M Brenan - One of the best experts on this subject based on the ideXlab platform.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:Abstract We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D < 0.2). Partition coefficients for Ir, Ru and Rh measured at more oxidizing conditions in this and previous studies are 10 to 1000 times higher than results from experiments using graphite capsules. We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
Ovidiu Oprea - One of the best experts on this subject based on the ideXlab platform.
-
chromium substituted copper ferrites via gluconate precursor route
Ceramics International, 2015Co-Authors: Ioana Mindru, Dana Gingasu, Luminita Patron, Gabriela Marinescu, Jose M Calderonmoreno, L Diamandescu, Silviu Preda, Ovidiu OpreaAbstract:Abstract CuFe 2− x Cr x O 4 Spinel (0≤ x ≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mossbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mossbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained Spinel powders depend on the concentration of Cr 3+ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic Spinel type structure for x =0.5, 1.0 and a tetragonal structure for x =0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mossbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe 2− x Cr x O 4 Spinels.
-
chromium substituted copper ferrites via gluconate precursor route
Ceramics International, 2015Co-Authors: Ioana Mindru, Dana Gingasu, Luminita Patron, Gabriela Marinescu, Jose M Calderonmoreno, L Diamandescu, Silviu Preda, Ovidiu OpreaAbstract:Abstract CuFe 2− x Cr x O 4 Spinel (0≤ x ≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mossbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mossbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained Spinel powders depend on the concentration of Cr 3+ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic Spinel type structure for x =0.5, 1.0 and a tetragonal structure for x =0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mossbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe 2− x Cr x O 4 Spinels.
Craig F Finnigan - One of the best experts on this subject based on the ideXlab platform.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:Abstract We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D < 0.2). Partition coefficients for Ir, Ru and Rh measured at more oxidizing conditions in this and previous studies are 10 to 1000 times higher than results from experiments using graphite capsules. We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
William F Mcdonough - One of the best experts on this subject based on the ideXlab platform.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:Abstract We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
-
experimental constraints on the partitioning of ru rh ir pt and pd between chromite and silicate melt the importance of ferric iron
Chemical Geology, 2012Co-Authors: James M Brenan, Craig F Finnigan, William F Mcdonough, Veronika HomolovaAbstract:We have performed partitioning experiments to assess the role of chromium-rich Spinel in controlling the behavior of the platinum-group elements (PGEs) during igneous differentiation. Spinels were equilibrated with natural and synthetic iron-bearing basalt at 0.1 MPa and 2 GPa at 1400–1900 °C over an fO2 range of IW + 1.6 to IW + 7. Results from relatively reduced, graphite-encapsulated experiments done at 2 GPa indicate that Ru is compatible in Cr-Spinel (mineral/melt partition coefficient, D, of ~ 4), followed by Rh and Ir, which are moderately incompatible (D range of 0.04 to ~ 1), with Pt and Pd the most incompatible (D < 0.2). Partition coefficients for Ir, Ru and Rh measured at more oxidizing conditions in this and previous studies are 10 to 1000 times higher than results from experiments using graphite capsules. We account for the variation in Spinel–melt partitioning with a model which considers both the affinity of the PGE cation for a particular Spinel lattice site, and the change in site occupancy accompanying the increase in ferric iron component with fO2. Assuming that Ir and Rh are present as divalent species, with a strong affinity for VI-fold coordination, DIr and DRh are predicted to rise rapidly with the ferric iron component, explaining the large D-values for magnetite-rich Spinels. Model results indicate that DIr ≤ 20 and DRh are ≤ 100 for ferric-iron poor, Cr-rich compositions, as would crystallize in komatiites, some layered intrusions, and ophiolites. The overall compatibility of Ru for chromite is consistent with the predominance of Ru3+ at experiment conditions and the similarity in the size of Ru3+ to Cr3+ and Fe3+. The increase in DRu with the ferric iron content of the Spinel likely involves a strong effect of mineral composition superimposed on a change in melt speciation (Ru2+ to Ru3+) with increased fO2. The effect of mineral composition is a consequence of the difference in octahedral site preference energy (OSPE) between Ru3+, Fe3+ and Cr3+, with stronger partitioning of Ru into Fe3+-rich compositions due to the enhanced reduction in energy gained by the Ru3+ substitution. Ru partition coefficients for ferric-iron poor Spinel are expected to be ~ 30, which is somewhat lower than values estimated from natural samples obtained from in situ chromite analyses. Results indicate that the ferric iron content of chromite exerts a strong control on the partitioning of some PGEs which should be taken into account in both future experimental work and in models of igneous differentiation.
