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Daniel E Harlov - One of the best experts on this subject based on the ideXlab platform.
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hydrothermal solubility of tbpo4 hopo4 tmpo4 and lupo4 Xenotime endmembers at ph of 2 and temperatures between 100 and 250 c
Chemical Geology, 2021Co-Authors: Daniel E Harlov, Alexander P GysiAbstract:Abstract Rare earth element (REE) phosphates such as Xenotime (YPO4) are important hosts to the heavy (H)REE in natural systems. Xenotime is commonly associated with hydrothermal alteration and mineral replacement reactions and its composition may yield important clues about the mineralization processes from aqueous fluids in critical mineral deposits. Robust underlying thermodynamic data for the REE phosphate endmembers and aqueous species are required to simulate the stability of Xenotime and the mobility of REE in natural hydrothermal fluids. In this study, the solubility of synthetic TbPO4, HoPO4, TmPO4, and LuPO4 endmembers has been measured in aqueous solutions between 100 and 250 ∘C at saturated water vapor pressure. The solubility products (Ks0) determined in the experiments were compared to values retrieved from a combination of calorimetric data for the REE phosphates and thermodynamic properties of the aqueous REE species at elevated temperatures. The solubility of Xenotime is retrograde and generally higher in the experiments than predicted by different sources of thermodynamic data. To resolve these discrepancies, the solubility data were used to optimize the thermodynamic properties of the REE phosphate endmembers and REE aqueous species. These optimizations permit retrieving a set of provisional standard Gibbs energies of formation for REE3+ and REEOH2+ at elevated temperature and were used to derive the following updated Ks0 values (uncertainty of ± 0.2 at the 95% confidence) for the reaction REEPO4 (s) = REE3+ + PO43−: t (∘C) logKs0(TbPO4) logKs0(HoPO4) logKs0(TmPO4) logKs0 (LuPO4) 100 −27.3 −27.7 −27.9 −28.1 150 −28.8 −29.2 −29.5 −29.6 200 −30.6 −30.9 −31.2 −31.4 250 −32.7 −32.9 −33.3 −33.4 The updated thermodynamic data generated from the solubility experiments have a significant impact on simulated Xenotime compositions and predicted mobility of REE in crustal fluids. Future efforts are necessary to better constrain the properties of REE hydroxyl species at elevated temperature and possible non-ideal solid solution behavior for REE with ionic sizes significantly different from Y3+.
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hydrothermal solubility of tbpo4 hopo4 tmpo4 and lupo4 Xenotime endmembers at ph of 2 and temperatures between 100 and 250 c
Chemical Geology, 2021Co-Authors: Daniel E Harlov, Alexander P Gysi, Christopher Van HoozenAbstract:Abstract Rare earth element (REE) phosphates such as Xenotime (YPO4) are important hosts to the heavy (H)REE in natural systems. Xenotime is commonly associated with hydrothermal alteration and mineral replacement reactions and its composition may yield important clues about the mineralization processes from aqueous fluids in REE mineral deposits. Robust underlying thermodynamic data for the REE phosphate endmembers and aqueous species are required to simulate the stability of Xenotime and the mobility of REE in natural hydrothermal fluids. In this study, the solubility of synthetic TbPO4, HoPO4, TmPO4, and LuPO4 endmembers has been measured in aqueous solutions between 100 and 250 ∘C at saturated water vapor pressure. The solubility products (Ks0) determined in the experiments were compared to values retrieved from a combination of calorimetric data for the REE phosphates and thermodynamic properties of the aqueous REE species at elevated temperatures. The solubility of Xenotime is retrograde and generally higher in the experiments than predicted by different sources of thermodynamic data. To resolve these discrepancies, the solubility data were used to optimize the thermodynamic properties of the REE phosphate endmembers and REE aqueous species. These optimizations permit retrieving a set of provisional standard Gibbs energy of formation for REE3+ and REEOH2+ at elevated temperature and were used to derive the following updated Ks0 values (uncertainty of ± 0.2 at the 95% confidence) for the reaction REEPO4 (s) = REE3+ + PO43−: t (∘C) logKs0(TbPO4) logKs0(HoPO4) logKs0(TmPO4) logKs0 (LuPO4) 100 −27.3 −27.7 −27.9 −28.1 150 −28.8 −29.2 −29.5 −29.6 200 −30.6 −30.9 −31.2 −31.4 250 −32.7 −32.9 −33.3 −33.4 The updated thermodynamic data generated from the solubility experiments have a significant impact on simulated Xenotime compositions and predicted mobility of REE in crustal fluids. Future efforts are necessary to better constrain the properties of REE hydroxyl species at elevated temperature and possible non-ideal solid solution behavior for REE with ionic sizes significantly different from Y3+.
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experimental constraints on the relative stabilities of the two systems monazite ce allanite ce fluorapatite and Xenotime y y hree rich epidote y hree rich fluorapatite in high ca and na ca environments under p t conditions of 200 1000 mpa and 450 750 c
Mineralogy and Petrology, 2017Co-Authors: Bartosz Budzyn, Daniel E Harlov, Jaroslaw Majka, Gabriela A KozubbudzynAbstract:The relative stabilities of phases within the two systems monazite-(Ce) – fluorapatite – allanite-(Ce) and Xenotime-(Y) – (Y,HREE)-rich fluorapatite – (Y,HREE)-rich epidote have been tested experimentally as a function of pressure and temperature in systems roughly replicating granitic to pelitic composition with high and moderate bulk CaO/Na2O ratios over a wide range of P-T conditions from 200 to 1000 MPa and 450 to 750 °C via four sets of experiments. These included (1) monazite-(Ce), labradorite, sanidine, biotite, muscovite, SiO2, CaF2, and 2 M Ca(OH)2; (2) monazite-(Ce), albite, sanidine, biotite, muscovite, SiO2, CaF2, Na2Si2O5, and H2O; (3) Xenotime-(Y), labradorite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, and 2 M Ca(OH)2; and (4) Xenotime-(Y), albite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, Na2Si2O5, and H2O. Monazite-(Ce) breakdown was documented in experimental sets (1) and (2). In experimental set (1), the Ca high activity (estimated bulk CaO/Na2O ratio of 13.3) promoted the formation of REE-rich epidote, allanite-(Ce), REE-rich fluorapatite, and fluorcalciobritholite at the expense of monazite-(Ce). In contrast, a bulk CaO/Na2O ratio of ~1.0 in runs in set (2) prevented the formation of REE-rich epidote and allanite-(Ce). The reacted monazite-(Ce) was partially replaced by REE-rich fluorapatite-fluorcalciobritholite in all runs, REE-rich steacyite in experiments at 450 °C, 200–1000 MPa, and 550 °C, 200–600 MPa, and minor cheralite in runs at 650–750 °C, 200–1000 MPa. The experimental results support previous natural observations and thermodynamic modeling of phase equilibria, which demonstrate that an increased CaO bulk content expands the stability field of allanite-(Ce) relative to monazite-(Ce) at higher temperatures indicating that the relative stabilities of monazite-(Ce) and allanite-(Ce) depend on the bulk CaO/Na2O ratio. The experiments also provide new insights into the re-equilibration of monazite-(Ce) via fluid-aided coupled dissolution-reprecipitation, which affects the Th-U-Pb system in runs at 450 °C, 200–1000 MPa, and 550 °C, 200–600 MPa. A lack of compositional alteration in the Th, U, and Pb in monazite-(Ce) at 550 °C, 800–1000 MPa, and in experiments at 650–750 °C, 200–1000 MPa indicates the limited influence of fluid-mediated alteration on volume diffusion under high P-T conditions. Experimental sets (3) and (4) resulted in Xenotime-(Y) breakdown and partial replacement by (Y,REE)-rich fluorapatite to Y-rich fluorcalciobritholite. Additionally, (Y,HREE)-rich epidote formed at the expense of Xenotime-(Y) in three runs with 2 M Ca(OH)2 fluid, at 550 °C, 800 MPa; 650 °C, 800 MPa; and 650 °C, 1000 MPa similar to the experiments involving monazite-(Ce). These results confirm that replacement of Xenotime-(Y) by (Y,HREE)-rich epidote is induced by a high Ca bulk content with a high CaO/Na2O ratio. These experiments demonstrate also that the relative stabilities of Xenotime-(Y) and (Y,HREE)-rich epidote are strongly controlled by pressure.
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experimental constraints on the relative stabilities of the two systems monazite ce allanite ce fluorapatite and Xenotime y y hree rich epidote y hree rich fluorapatite in high ca and na ca environments under p t conditions of 200 1000 mpa and 450 750 c
Mineralogy and Petrology, 2017Co-Authors: Bartosz Budzyn, Daniel E Harlov, Jaroslaw Majka, Gabriela A KozubbudzynAbstract:The relative stabilities of phases within the two systems monazite-(Ce) - fluorapatite - allanite-(Ce) and Xenotime-(Y) - (Y,HREE)-rich fluorapatite - (Y,HREE)-rich epidote have been tested experimentally as a function of pressure and temperature in systems roughly replicating granitic to pelitic composition with high and moderate bulk CaO/Na2O ratios over a wide range of P-T conditions from 200 to 1000 MPa and 450 to 750 A degrees C via four sets of experiments. These included (1) monazite-(Ce), labradorite, sanidine, biotite, muscovite, SiO2, CaF2, and 2 M Ca(OH)(2); (2) monazite-(Ce), albite, sanidine, biotite, muscovite, SiO2, CaF2, Na2Si2O5, and H2O; (3) Xenotime-(Y), labradorite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, and 2 M Ca(OH)(2); and (4) Xenotime-(Y), albite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, Na2Si2O5, and H2O. Monazite-(Ce) breakdown was documented in experimental sets (1) and (2). In experimental set (1), the Ca high activity (estimated bulk CaO/Na2O ratio of 13.3) promoted the formation of REE-rich epidote, allanite-(Ce), REE-rich fluorapatite, and fluorcalciobritholite at the expense of monazite-(Ce). In contrast, a bulk CaO/Na2O ratio of similar to 1.0 in runs in set (2) prevented the formation of REE-rich epidote and allanite-(Ce). The reacted monazite-(Ce) was partially replaced by REE-rich fluorapatite-fluorcalciobritholite in all runs, REE-rich steacyite in experiments at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa, and minor cheralite in runs at 650-750 A degrees C, 200-1000 MPa. The experimental results support previous natural observations and thermodynamic modeling of phase equilibria, which demonstrate that an increased CaO bulk content expands the stability field of allanite-(Ce) relative to monazite-(Ce) at higher temperatures indicating that the relative stabilities of monazite-(Ce) and allanite-(Ce) depend on the bulk CaO/Na2O ratio. The experiments also provide new insights into the re-equilibration of monazite-(Ce) via fluid-aided coupled dissolution-reprecipitation, which affects the Th-U-Pb system in runs at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa. A lack of compositional alteration in the Th, U, and Pb in monazite-(Ce) at 550 A degrees C, 800-1000 MPa, and in experiments at 650-750 A degrees C, 200-1000 MPa indicates the limited influence of fluid-mediated alteration on volume diffusion under high P-T conditions. Experimental sets (3) and (4) resulted in Xenotime-(Y) breakdown and partial replacement by (Y,REE)-rich fluorapatite to Y-rich fluorcalciobritholite. Additionally, (Y,HREE)-rich epidote formed at the expense of Xenotime-(Y) in three runs with 2 M Ca(OH)(2) fluid, at 550 A degrees C, 800 MPa; 650 A degrees C, 800 MPa; and 650 A degrees C, 1000 MPa similar to the experiments involving monazite-(Ce). These results confirm that replacement of Xenotime-(Y) by (Y,HREE)-rich epidote is induced by a high Ca bulk content with a high CaO/Na2O ratio. These experiments demonstrate also that the relative stabilities of Xenotime-(Y) and (Y,HREE)-rich epidote are strongly controlled by pressure.
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fluorapatite monazite allanite relations in the grangesberg apatite iron oxide ore district bergslagen sweden
American Mineralogist, 2016Co-Authors: Erik Jonsson, Daniel E Harlov, Jaroslaw Majka, Karin Hogdahl, Katarina PerssonnilssonAbstract:Fluorapatite-monazite-Xenotime-allanite mineralogy, petrology, and textures are described for a suite of Kiruna-type apatite-iron oxide ore bodies from the Grangesberg Mining District in the Bergslagen ore province, south central Sweden. Fluorapatite occurs in three main lithological assemblages. These include: (1) the apatite-iron oxide ore bodies, (2) breccias associated with the ore bodies, which contain fragmented fluorapatite crystals, and (3) the variably altered host rocks, which contain sporadic, isolated fluorapatite grains or aggregates that are occasionally associated with magnetite in the silicate mineral matrix. Fluorapatite associated with the ore bodies is often zoned, with the outer rim enriched in Y+REE compared to the inner core. It contains sparse monazite inclusions. In the breccia, fluorapatite is rich in monazite-(Ce) ± Xenotime-(Y) inclusions, especially in its cores, along with reworked, larger monazite grains along fluorapatite and other mineral grain rims. In the host rocks, a small subset of the fluorapatite grains contain monazite ± Xenotime inclusions, while the large majority are devoid of inclusions. Overall, these monazites are relatively poor in Th and U. Allanite-(Ce) is found as inclusions and crack fillings in the fluorapatite from all three assemblage types as well as in the form of independent grains in the surrounding silicate mineral matrix in the host rocks. The apatite-iron oxide ore bodies are proposed to have an igneous, subvolcanic origin, potentially accompanied by explosive eruptions, which were responsible for the accompanying fluorapatite-rich breccias. Metasomatic alteration of the ore bodies probably began during the later stages of crystallization from residual, magmatically derived HCl- and H2SO4-bearing fluids present along grain boundaries. This was most likely followed by fluid exchange between the ore and its host rocks, both immediately after emplacement of the apatite-iron oxide body, and during subsequent phases of regional metamorphism and deformation.
Jaroslaw Majka - One of the best experts on this subject based on the ideXlab platform.
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experimental constraints on the relative stabilities of the two systems monazite ce allanite ce fluorapatite and Xenotime y y hree rich epidote y hree rich fluorapatite in high ca and na ca environments under p t conditions of 200 1000 mpa and 450 750 c
Mineralogy and Petrology, 2017Co-Authors: Bartosz Budzyn, Daniel E Harlov, Jaroslaw Majka, Gabriela A KozubbudzynAbstract:The relative stabilities of phases within the two systems monazite-(Ce) - fluorapatite - allanite-(Ce) and Xenotime-(Y) - (Y,HREE)-rich fluorapatite - (Y,HREE)-rich epidote have been tested experimentally as a function of pressure and temperature in systems roughly replicating granitic to pelitic composition with high and moderate bulk CaO/Na2O ratios over a wide range of P-T conditions from 200 to 1000 MPa and 450 to 750 A degrees C via four sets of experiments. These included (1) monazite-(Ce), labradorite, sanidine, biotite, muscovite, SiO2, CaF2, and 2 M Ca(OH)(2); (2) monazite-(Ce), albite, sanidine, biotite, muscovite, SiO2, CaF2, Na2Si2O5, and H2O; (3) Xenotime-(Y), labradorite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, and 2 M Ca(OH)(2); and (4) Xenotime-(Y), albite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, Na2Si2O5, and H2O. Monazite-(Ce) breakdown was documented in experimental sets (1) and (2). In experimental set (1), the Ca high activity (estimated bulk CaO/Na2O ratio of 13.3) promoted the formation of REE-rich epidote, allanite-(Ce), REE-rich fluorapatite, and fluorcalciobritholite at the expense of monazite-(Ce). In contrast, a bulk CaO/Na2O ratio of similar to 1.0 in runs in set (2) prevented the formation of REE-rich epidote and allanite-(Ce). The reacted monazite-(Ce) was partially replaced by REE-rich fluorapatite-fluorcalciobritholite in all runs, REE-rich steacyite in experiments at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa, and minor cheralite in runs at 650-750 A degrees C, 200-1000 MPa. The experimental results support previous natural observations and thermodynamic modeling of phase equilibria, which demonstrate that an increased CaO bulk content expands the stability field of allanite-(Ce) relative to monazite-(Ce) at higher temperatures indicating that the relative stabilities of monazite-(Ce) and allanite-(Ce) depend on the bulk CaO/Na2O ratio. The experiments also provide new insights into the re-equilibration of monazite-(Ce) via fluid-aided coupled dissolution-reprecipitation, which affects the Th-U-Pb system in runs at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa. A lack of compositional alteration in the Th, U, and Pb in monazite-(Ce) at 550 A degrees C, 800-1000 MPa, and in experiments at 650-750 A degrees C, 200-1000 MPa indicates the limited influence of fluid-mediated alteration on volume diffusion under high P-T conditions. Experimental sets (3) and (4) resulted in Xenotime-(Y) breakdown and partial replacement by (Y,REE)-rich fluorapatite to Y-rich fluorcalciobritholite. Additionally, (Y,HREE)-rich epidote formed at the expense of Xenotime-(Y) in three runs with 2 M Ca(OH)(2) fluid, at 550 A degrees C, 800 MPa; 650 A degrees C, 800 MPa; and 650 A degrees C, 1000 MPa similar to the experiments involving monazite-(Ce). These results confirm that replacement of Xenotime-(Y) by (Y,HREE)-rich epidote is induced by a high Ca bulk content with a high CaO/Na2O ratio. These experiments demonstrate also that the relative stabilities of Xenotime-(Y) and (Y,HREE)-rich epidote are strongly controlled by pressure.
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experimental constraints on the relative stabilities of the two systems monazite ce allanite ce fluorapatite and Xenotime y y hree rich epidote y hree rich fluorapatite in high ca and na ca environments under p t conditions of 200 1000 mpa and 450 750 c
Mineralogy and Petrology, 2017Co-Authors: Bartosz Budzyn, Daniel E Harlov, Jaroslaw Majka, Gabriela A KozubbudzynAbstract:The relative stabilities of phases within the two systems monazite-(Ce) – fluorapatite – allanite-(Ce) and Xenotime-(Y) – (Y,HREE)-rich fluorapatite – (Y,HREE)-rich epidote have been tested experimentally as a function of pressure and temperature in systems roughly replicating granitic to pelitic composition with high and moderate bulk CaO/Na2O ratios over a wide range of P-T conditions from 200 to 1000 MPa and 450 to 750 °C via four sets of experiments. These included (1) monazite-(Ce), labradorite, sanidine, biotite, muscovite, SiO2, CaF2, and 2 M Ca(OH)2; (2) monazite-(Ce), albite, sanidine, biotite, muscovite, SiO2, CaF2, Na2Si2O5, and H2O; (3) Xenotime-(Y), labradorite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, and 2 M Ca(OH)2; and (4) Xenotime-(Y), albite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, Na2Si2O5, and H2O. Monazite-(Ce) breakdown was documented in experimental sets (1) and (2). In experimental set (1), the Ca high activity (estimated bulk CaO/Na2O ratio of 13.3) promoted the formation of REE-rich epidote, allanite-(Ce), REE-rich fluorapatite, and fluorcalciobritholite at the expense of monazite-(Ce). In contrast, a bulk CaO/Na2O ratio of ~1.0 in runs in set (2) prevented the formation of REE-rich epidote and allanite-(Ce). The reacted monazite-(Ce) was partially replaced by REE-rich fluorapatite-fluorcalciobritholite in all runs, REE-rich steacyite in experiments at 450 °C, 200–1000 MPa, and 550 °C, 200–600 MPa, and minor cheralite in runs at 650–750 °C, 200–1000 MPa. The experimental results support previous natural observations and thermodynamic modeling of phase equilibria, which demonstrate that an increased CaO bulk content expands the stability field of allanite-(Ce) relative to monazite-(Ce) at higher temperatures indicating that the relative stabilities of monazite-(Ce) and allanite-(Ce) depend on the bulk CaO/Na2O ratio. The experiments also provide new insights into the re-equilibration of monazite-(Ce) via fluid-aided coupled dissolution-reprecipitation, which affects the Th-U-Pb system in runs at 450 °C, 200–1000 MPa, and 550 °C, 200–600 MPa. A lack of compositional alteration in the Th, U, and Pb in monazite-(Ce) at 550 °C, 800–1000 MPa, and in experiments at 650–750 °C, 200–1000 MPa indicates the limited influence of fluid-mediated alteration on volume diffusion under high P-T conditions. Experimental sets (3) and (4) resulted in Xenotime-(Y) breakdown and partial replacement by (Y,REE)-rich fluorapatite to Y-rich fluorcalciobritholite. Additionally, (Y,HREE)-rich epidote formed at the expense of Xenotime-(Y) in three runs with 2 M Ca(OH)2 fluid, at 550 °C, 800 MPa; 650 °C, 800 MPa; and 650 °C, 1000 MPa similar to the experiments involving monazite-(Ce). These results confirm that replacement of Xenotime-(Y) by (Y,HREE)-rich epidote is induced by a high Ca bulk content with a high CaO/Na2O ratio. These experiments demonstrate also that the relative stabilities of Xenotime-(Y) and (Y,HREE)-rich epidote are strongly controlled by pressure.
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fluorapatite monazite allanite relations in the grangesberg apatite iron oxide ore district bergslagen sweden
American Mineralogist, 2016Co-Authors: Erik Jonsson, Daniel E Harlov, Jaroslaw Majka, Karin Hogdahl, Katarina PerssonnilssonAbstract:Fluorapatite-monazite-Xenotime-allanite mineralogy, petrology, and textures are described for a suite of Kiruna-type apatite-iron oxide ore bodies from the Grangesberg Mining District in the Bergslagen ore province, south central Sweden. Fluorapatite occurs in three main lithological assemblages. These include: (1) the apatite-iron oxide ore bodies, (2) breccias associated with the ore bodies, which contain fragmented fluorapatite crystals, and (3) the variably altered host rocks, which contain sporadic, isolated fluorapatite grains or aggregates that are occasionally associated with magnetite in the silicate mineral matrix. Fluorapatite associated with the ore bodies is often zoned, with the outer rim enriched in Y+REE compared to the inner core. It contains sparse monazite inclusions. In the breccia, fluorapatite is rich in monazite-(Ce) ± Xenotime-(Y) inclusions, especially in its cores, along with reworked, larger monazite grains along fluorapatite and other mineral grain rims. In the host rocks, a small subset of the fluorapatite grains contain monazite ± Xenotime inclusions, while the large majority are devoid of inclusions. Overall, these monazites are relatively poor in Th and U. Allanite-(Ce) is found as inclusions and crack fillings in the fluorapatite from all three assemblage types as well as in the form of independent grains in the surrounding silicate mineral matrix in the host rocks. The apatite-iron oxide ore bodies are proposed to have an igneous, subvolcanic origin, potentially accompanied by explosive eruptions, which were responsible for the accompanying fluorapatite-rich breccias. Metasomatic alteration of the ore bodies probably began during the later stages of crystallization from residual, magmatically derived HCl- and H2SO4-bearing fluids present along grain boundaries. This was most likely followed by fluid exchange between the ore and its host rocks, both immediately after emplacement of the apatite-iron oxide body, and during subsequent phases of regional metamorphism and deformation.
Alexander P Gysi - One of the best experts on this subject based on the ideXlab platform.
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hydrothermal solubility of tbpo4 hopo4 tmpo4 and lupo4 Xenotime endmembers at ph of 2 and temperatures between 100 and 250 c
Chemical Geology, 2021Co-Authors: Daniel E Harlov, Alexander P GysiAbstract:Abstract Rare earth element (REE) phosphates such as Xenotime (YPO4) are important hosts to the heavy (H)REE in natural systems. Xenotime is commonly associated with hydrothermal alteration and mineral replacement reactions and its composition may yield important clues about the mineralization processes from aqueous fluids in critical mineral deposits. Robust underlying thermodynamic data for the REE phosphate endmembers and aqueous species are required to simulate the stability of Xenotime and the mobility of REE in natural hydrothermal fluids. In this study, the solubility of synthetic TbPO4, HoPO4, TmPO4, and LuPO4 endmembers has been measured in aqueous solutions between 100 and 250 ∘C at saturated water vapor pressure. The solubility products (Ks0) determined in the experiments were compared to values retrieved from a combination of calorimetric data for the REE phosphates and thermodynamic properties of the aqueous REE species at elevated temperatures. The solubility of Xenotime is retrograde and generally higher in the experiments than predicted by different sources of thermodynamic data. To resolve these discrepancies, the solubility data were used to optimize the thermodynamic properties of the REE phosphate endmembers and REE aqueous species. These optimizations permit retrieving a set of provisional standard Gibbs energies of formation for REE3+ and REEOH2+ at elevated temperature and were used to derive the following updated Ks0 values (uncertainty of ± 0.2 at the 95% confidence) for the reaction REEPO4 (s) = REE3+ + PO43−: t (∘C) logKs0(TbPO4) logKs0(HoPO4) logKs0(TmPO4) logKs0 (LuPO4) 100 −27.3 −27.7 −27.9 −28.1 150 −28.8 −29.2 −29.5 −29.6 200 −30.6 −30.9 −31.2 −31.4 250 −32.7 −32.9 −33.3 −33.4 The updated thermodynamic data generated from the solubility experiments have a significant impact on simulated Xenotime compositions and predicted mobility of REE in crustal fluids. Future efforts are necessary to better constrain the properties of REE hydroxyl species at elevated temperature and possible non-ideal solid solution behavior for REE with ionic sizes significantly different from Y3+.
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hydrothermal solubility of tbpo4 hopo4 tmpo4 and lupo4 Xenotime endmembers at ph of 2 and temperatures between 100 and 250 c
Chemical Geology, 2021Co-Authors: Daniel E Harlov, Alexander P Gysi, Christopher Van HoozenAbstract:Abstract Rare earth element (REE) phosphates such as Xenotime (YPO4) are important hosts to the heavy (H)REE in natural systems. Xenotime is commonly associated with hydrothermal alteration and mineral replacement reactions and its composition may yield important clues about the mineralization processes from aqueous fluids in REE mineral deposits. Robust underlying thermodynamic data for the REE phosphate endmembers and aqueous species are required to simulate the stability of Xenotime and the mobility of REE in natural hydrothermal fluids. In this study, the solubility of synthetic TbPO4, HoPO4, TmPO4, and LuPO4 endmembers has been measured in aqueous solutions between 100 and 250 ∘C at saturated water vapor pressure. The solubility products (Ks0) determined in the experiments were compared to values retrieved from a combination of calorimetric data for the REE phosphates and thermodynamic properties of the aqueous REE species at elevated temperatures. The solubility of Xenotime is retrograde and generally higher in the experiments than predicted by different sources of thermodynamic data. To resolve these discrepancies, the solubility data were used to optimize the thermodynamic properties of the REE phosphate endmembers and REE aqueous species. These optimizations permit retrieving a set of provisional standard Gibbs energy of formation for REE3+ and REEOH2+ at elevated temperature and were used to derive the following updated Ks0 values (uncertainty of ± 0.2 at the 95% confidence) for the reaction REEPO4 (s) = REE3+ + PO43−: t (∘C) logKs0(TbPO4) logKs0(HoPO4) logKs0(TmPO4) logKs0 (LuPO4) 100 −27.3 −27.7 −27.9 −28.1 150 −28.8 −29.2 −29.5 −29.6 200 −30.6 −30.9 −31.2 −31.4 250 −32.7 −32.9 −33.3 −33.4 The updated thermodynamic data generated from the solubility experiments have a significant impact on simulated Xenotime compositions and predicted mobility of REE in crustal fluids. Future efforts are necessary to better constrain the properties of REE hydroxyl species at elevated temperature and possible non-ideal solid solution behavior for REE with ionic sizes significantly different from Y3+.
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experimental determination of the high temperature heat capacity of a natural Xenotime y solid solution and synthetic dypo 4 and erpo 4 endmembers
Thermochimica Acta, 2016Co-Authors: Alexander P Gysi, Daniel E Harlov, Deusavan Costa Filho, Anthony E WilliamsjonesAbstract:Abstract The heat capacity of natural Xenotime-(Y) and synthetic DyPO 4 and ErPO 4 crystals was determined by differential scanning calorimetry (DSC) at temperatures of 298.15 K to 868.15 K and a pressure of 0.1 MPa. The aim of the study was to develop a method to accurately measure the isobaric heat capacity ( C P ) of rare earth element (REE) phosphates, compare the results to data from adiabatic calorimetric experiments, and evaluate the deviation from ideality of the C P of the natural Xenotime-(Y) solid solution. The measured C P data (in J mol −1 K −1 ) can be described by the relationships: 185.5 − 751.9T −0.5 − 3.261e + 06 T −2 for DyPO 4 ; 207.2 − 1661T −0.5 − 5.289e + 05 T −2 for ErPO 4 ; and 208 − 1241T −0.5 − 2.493e + 06 T −2 for Xenotime-(Y); where T is the temperature in K. The heat capacity data for natural Xenotime-(Y) were used to determine the excess function for the solid solution, which yields an excess heat capacity ranging between 7.9 and 10.7%, well within the range of the DSC method used in this study. The experiments indicate that Xenotime-(Y) forms a non-ideal solid solution. Future DSC studies will provide important data for developing a solid solution model for the incorporation of REE in Xenotime-(Y).
Calvin F Miller - One of the best experts on this subject based on the ideXlab platform.
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accessory mineral behavior during differentiation of a granite suite monazite Xenotime and zircon in the sweetwater wash pluton southeastern california u s a
Chemical Geology, 1993Co-Authors: D Wark, Calvin F MillerAbstract:Abstract Compositional and textural characteristics of the accessory minerals monazite, Xenotime and zircon in the Sweetwater Wash granites and related aplites indicate that these phases not only controlled much of the trace-element geochemistry of the suite, but that they also record the melt compositional changes that occurred during magmatic differentiation. Fractionation of monazite due to decreasing saturation levels of its essential structural constituents with falling temperature was likely responsible for an ongoing trend of light rare-earth element (REE) depletion. This was accompanied by increasing heavy-REE concentrations until Xenotime joined the crystallizing assemblage; subsequently, combined monazite-Xenotime fractionation resulted in lowering of the entire REE budget. Zircon, which contains inherited cores that were apparently resorbed and rounded during initial anatexis, was saturated throughout the differentiation history of the Sweetwater Wash suite. Accessory phases in granite and aplite exhibit strong compositional differences at a variety of scales. The differences are best displayed by monazite: on average, crystals in more differentiated rocks (aplites) are relatively depleted in light REE's and contain higher concentrations of the substituting elements U and Th. Zircon displays complimentary increases in Hf and Y, while Xenotime shows a slight increase in Th and in Gd/Ho ratios; both phases also exhibit higher U concentrations in aplites than in granites. These differences in accessory mineral compositions are observed not only between granites and the more differentiated aplites, but also within individual thin sections, due to in situ fractionation. On an even smaller scale, strong compositional variations are present within single crystals, possibly due to diffusion-controlled melt-compositional gradients in the regions (a) adjacent to growing major phases, and (b) adjacent to the growing accessory crystal itself. Our observations indicate that compositional variations among accessory minerals are potentially useful for tracking of magmatic processes, but that the scale of observed variations must be carefully considered.
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accessory mineral behavior during differentiation of a granite suite monazite Xenotime and zircon in the sweetwater wash pluton southeastern california usa
V. M. Goldschmidt conference, 1993Co-Authors: D Wark, Calvin F MillerAbstract:Compositional and textural characteristics of the accessory minerals monazite, Xenotime and zircon in the Sweetwater Wash granites and related aplites indicate that these phases not only controlled much of the trace-element geochemistry of the suite, but that they also record the melt compositional changes that occurred during magmatic differentiation. Fractionation of monazite due to decreasing saturation levels of its essential structural constituents with falling temperature was likely responsible for an ongoing trend of light rare-earth element (REE) depletion. This was accompanied by increasing heavy-REE concentrations until Xenotime joined the crystallizing assemblage; subsequently, combined monazite-Xenotime fractionation resulted in lowering of the entire REE budget
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quartz apatite ree phosphates uraninite vein mineralization near cucma eastern slovakia a product of early alpine hydrothermal activity in the gemeric superunit western carpathians
Journal of Geosciences, 2014Co-Authors: Martin Stevko, Pavel Uher, Martin Ondrejka, Daniel Ozdin, Peter BacikAbstract:The quartz veins with primary fluorapatite, Xenotime-(Y), monazite-(Ce) to monazite-(Nd), uraninite, and secondary florencite-(Ce) and goyazite occur in Lower Devonian metavolcano-sedimentary sequence of the Gelnica Group, Gemeric Superunit, the Central Western Carpathians (eastern Slovakia). They represent an example of hydrothermal REE–U mineralization. Fluorapatite forms parallel bands of columnar crystals (≤ 3 cm) in massive quartz. Monazite(Ce) to (Nd) shows a near end-member composition with very small amounts of cheralite and huttonite components. Widespread Xenotime-(Y) forms colloform aggregates or irregular aggregates in association with fluorapatite and monazite. Uraninite electron-microprobe U–Pb dating gave the average age of 207 ± 2 Ma (n = 16, 2σ), which is consistent with formation of the U mineralization in the Gemeric Superunit (e.g., Kuriskova uranium deposit) during early Alpine hydrothermal activity.
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magmatic and post magmatic y ree th phosphate silicate and nb ta y ree oxide minerals in a type metagranite an example from the turcok massif the western carpathians slovakia
Mineralogical Magazine, 2009Co-Authors: Pavel Uher, Martin Ondrejka, Patrik KonecnýAbstract:An electron microprobe study of Y- REE -Th phosphate, silicate and Nb-Ta-Y- REE accessory-mineral assemblages revealed the compositional variations and evolution in post-orogenic, hypersolvus Permian A-type metagranite from Turcok, in the Gemeric Unit, of the Western Carpathians, eastern Slovakia. Prismatic zircon I and allanite-(Ce) are primary magmatic phases. However, the late-magmatic to earlysubsolidus processes led to the formation of a more complex younger assemblage: bipyramidal zircon II, Xenotime-(Y), thorite, gadolinite-hingganite-(Y), Nb-Ta-Y- REE oxide phases [fergusonite-(beta)/samarskite-(Y), aeschynite/polycrase-(Y), and Nb-rich rutile?] and possibly monazite-(Ce). However, monazite-(Ce) and the partial alteration of allanite-(Ce), Xenotime-(Y) and the Nb-Ta-Y- REE minerals are probably connected with a younger Alpine metamorphic overprint of the granite. Thorite appears as a solid solution in the thorite-Xenotime-zircon series; it is also enriched in Al. Fergusonite-(beta)/samarskite-(Y) and especially aeschynite/polycrase-(Y) show increased P, Si and Al contents.
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arsenian monazite ce and Xenotime y ree arsenates and carbonates from the tisovec rejkovo rhyolite western carpathians slovakia composition and substitutions in the ree y xo4 system x p as si nb s
Lithos, 2007Co-Authors: Martin Ondrejka, Pavel Uher, Jaroslav Prsek, Daniel OzdinAbstract:Abstract A unique REE–Y–(Th)–P–As–(Si)–(Nb)–(S) accessory assemblage was identified in a small body of Lower Triassic A-type rhyolite of the Silicic Superunit near Tisovec-Rejkovo, Central Slovakia. Arsenian monazite-(Ce)–phosphatian gasparite-(Ce) and arsenian Xenotime-(Y)–phosphatian chernovite-(Y) solid solutions in association with REE carbonates (bastnasite, parisite, rontgenite?, synchysite) and rare cerianite-(Ce) form anhedral to subhedral grains and aggregates (≤ 0.3 mm), scattered in the groundass or as intergrowths with zircon and Fe–Ti oxides. Compositions show a wide AsP− 1 substitution in monazite–gasparite and Xenotime–chernovite solid solutions; atom. % As/(As+P) = 0.00 to 0.73 and 0.10 to 0.94, respectively. The presence of S in monazite–gasparite s.s. (≤ 0.14 apfu), together with Ca enrichment indicates “clinoanhydrite“ substitution, CaS(REE,Y)− 1 (P,As)− 1, rather than the incorporation of brabantite, along the CaTh(REE,Y)− 2 exchange vector. Moreover, the Th- and Nb-rich members reveal thorite and fergusonite substitutions, ThSi(Y,REE)− 1 (P,As)− 1 and Nb(P,As)− 1, respectively. The As-rich REE phases originated probably during the post-magmatic alteration of primary monazite-(Ce) and Xenotime-(Y) by As-rich, high fO2 fluids, whereas cerianite-(Ce) and the REE carbonates are products of a later hydrothermal overprint of the rhyolite by CO2-rich solutions.
