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Matthias Gottschalk - One of the best experts on this subject based on the ideXlab platform.
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crystal chemistry of synthetic ca2al3si3o12oh sr2al3si3o12oh solid solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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Crystal chemistry of synthetic Ca2Al3Si3O12OH–Sr2Al3Si3O12OH solid-solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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thermodynamic properties of zoisite Clinozoisite and epidote
Reviews in Mineralogy & Geochemistry, 2004Co-Authors: Matthias GottschalkAbstract:The natural occurrence of epidote minerals is widespread over a large variety of geological settings. Thus epidote minerals are part of numerous phase equilibria, which need to be evaluated to understand the geological processes in general. There are two principal approaches to evaluate phase equilibria in the deep earth. The first uses direct experimental investigations, while the second is by thermodynamic calculations and modeling. Performing and evaluating experiments is often a tedious procedure and by far not all systems can be studied at the required physical and chemical conditions, considering all of the possible variables. Therefore experimental investigations are in many instances only case studies in simplified systems, but the thermodynamic framework provides a powerful tool to perform calculations of complex phase equilibria, if the required parameters are available. However, these two approaches are not necessarily independent, because experimental results are often used to evaluate and to calibrate physical-chemical parameters for such calculations. Many physical-chemical textbooks treat the principles of thermodynamics, and in addition some texts (e.g., Anderson and Crerar 1993; Nordstrom and Munoz 1994) introduce its application to the geological sciences. Therefore only the fundamental equations and their relationship to the required parameters are treated here briefly. The evaluation of phase equilibria and/or stable phase assemblages involves the calculation of the apparent chemical potential μ i ( P , T ) for each component i present at the P and T of choice according to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[{\mu}\_{\mathit{i(P,T)}}\ =\ {\Delta}\_{\mathit{f}}\mathit{h^{o}\_{i(P\_{r},T\_{r})}}\ {-}\ \mathit{TS\_{i(P\_{r},T\_{r})}}^{o}\ +\ {{\int}\_{\mathit{T\_{r}}}^{\mathit{T}}}\mathit{c}^{o}\mathit{\_{Pi(T)}dT\ {-}\ T}{\_{\mathit{T\_{r}}}^{\mathit{T}}}\frac{\mathit{c}^{o}\_{\mathit{Pi(T)}}}{\mathit{T}}\mathit{dT}\ +\ {{\int}\_{\mathit{P\_{r}}}^{\mathit{P}}}{\nu}^{o}\_{\mathit{i(P,T)}}\mathit{dP}\ +\ \mathit{RT}\ ln\mathit{a\_{i}}\] \end{document}(1) The calculation involves the following molar standard state properties (note small letters designate molar quantities): absolute enthalpy of formation from the elements Δ f h i ° and third law entropy s i ° at reference conditions P r and T r (i.e., 0.1 MPa, 298.15 K), the heat capacity c P ° i at constant pressure as function of temperature, and the …
Gerhard Franz - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of zoisite–Clinozoisite phase equilibria in the system CaO–Fe 2 O 3 –Al 2 O 3 –SiO 2 –H 2 O
Contributions to Mineralogy and Petrology, 2020Co-Authors: A Brunsmann, Gerhard Franz, W HeinrichAbstract:The system Ca2Al3Si3O11(O/OH)–Ca2Al2FeSi3O11(O/OH), with emphasis on the Al-rich portion, was investigated by synthesis experiments at 0.5 and 2.0 GPa, 500–800 °C, using the technique of producing overgrowths on natural seed crystals. Electron microprobe analyses of overgrowths up to >100 µm wide have located the phase transition from Clinozoisite to zoisite as a function of P–T–Xps and a miscibility gap in the Clinozoisite solid solution. The experiments confirm a narrow, steep zoisite–Clinozoisite two-phase loop in T–Xps section. Maximum and minimum iron contents in coexisting zoisite and Clinozoisite are given by \({\rm X}_{{\rm ps}}^{{\rm zo}} {\rm (max) = 1}{\rm .9*10}^{ - 4} T{\rm + 3}{\rm .1*10}^{ - 2} P - {\rm 5}{\rm .36*10}^{ - 2} \) and \({\rm X}_{{\rm ps}}^{{\rm czo}} {\rm (min)} = {\rm (4}{\rm .6} * {\rm 10}^{ - {\rm 4}} - 4 * {\rm 10}^{ - {\rm 5}} P{\rm )}T + {\rm 3}{\rm .82} * {\rm 10}^{ - {\rm 2}} P - {\rm 8}{\rm .76} * {\rm 10}^{ - {\rm 2}} \) (P in GPa, T in °C). The iron-free end member reaction Clinozoisite = zoisite has equilibrium temperatures of 185±50 °C at 0.5 GPa and 0±50 °C at 2.0 GPa, with ΔHr0=2.8±1.3 kJ/mol and ΔSr0=4.5±1.4 J/mol×K. At 0.5 GPa, two Clinozoisite modifications exist, which have compositions of Clinozoisite I ~0.15 to 0.25 Xps and Clinozoisite II >0.55 Xps. The upper thermal stability of Clinozoisite I at 0.5 GPa lies slightly above 600 °C, whereas Fe-rich Clinozoisite II is stable at 650 °C. The schematic phase relations between epidote minerals, grossular-andradite solid solutions and other phases in the system CaO–Al2O3–Fe2O3–SiO2–H2O are shown.
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crystal chemistry of synthetic ca2al3si3o12oh sr2al3si3o12oh solid solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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Crystal chemistry of synthetic Ca2Al3Si3O12OH–Sr2Al3Si3O12OH solid-solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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unusual deformation microstructures in garnet titanite and Clinozoisite from an eclogite of the lower schist cover tauern window austria
European Journal of Mineralogy, 2004Co-Authors: Wolfgang Friedrich Muller, Gerhard FranzAbstract:An eclogite sample from the Lower Schist Cover of the Tauern Window, only a few tens of metres distant from the intercalated Eclogite Zone, was studied by transmission electron microscopy. Garnet, titanite and Clinozoisite reveal unusual deformation microstructures not reported before from natural occurrences. Garnet shows polygonisation into subgrains of only 0.5 to 3 μm in size which are separated by low angle grain boundaries. The subgrain cells show a preferred orientation parallel to (110). In titanite, most of the numerous dislocations are organized into low angle grain boundaries with Burgers vectors parallel to . The Burgers vector of free dislocations is [100]. Weak fringes in the wake of dislocations are interpreted as slip traces. Clinozoisite contains submicroscopic mechanical twin lamellae parallel to (100); the twin law is m parallel to (100). The unusual deformation features are explained as the result of imbrication of the Eclogite Zone.
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experimental investigation of zoisite Clinozoisite phase equilibria in the system cao fe 2 o 3 al 2 o 3 sio 2 h 2 o
Contributions to Mineralogy and Petrology, 2002Co-Authors: A Brunsmann, Gerhard Franz, W HeinrichAbstract:The system Ca2Al3Si3O11(O/OH)–Ca2Al2FeSi3O11(O/OH), with emphasis on the Al-rich portion, was investigated by synthesis experiments at 0.5 and 2.0 GPa, 500–800 °C, using the technique of producing overgrowths on natural seed crystals. Electron microprobe analyses of overgrowths up to >100 µm wide have located the phase transition from Clinozoisite to zoisite as a function of P–T–Xps and a miscibility gap in the Clinozoisite solid solution. The experiments confirm a narrow, steep zoisite–Clinozoisite two-phase loop in T–Xps section. Maximum and minimum iron contents in coexisting zoisite and Clinozoisite are given by \({\rm X}_{{\rm ps}}^{{\rm zo}} {\rm (max) = 1}{\rm .9*10}^{ - 4} T{\rm + 3}{\rm .1*10}^{ - 2} P - {\rm 5}{\rm .36*10}^{ - 2} \) and \({\rm X}_{{\rm ps}}^{{\rm czo}} {\rm (min)} = {\rm (4}{\rm .6} * {\rm 10}^{ - {\rm 4}} - 4 * {\rm 10}^{ - {\rm 5}} P{\rm )}T + {\rm 3}{\rm .82} * {\rm 10}^{ - {\rm 2}} P - {\rm 8}{\rm .76} * {\rm 10}^{ - {\rm 2}} \) (P in GPa, T in °C). The iron-free end member reaction Clinozoisite = zoisite has equilibrium temperatures of 185±50 °C at 0.5 GPa and 0±50 °C at 2.0 GPa, with ΔHr0=2.8±1.3 kJ/mol and ΔSr0=4.5±1.4 J/mol×K. At 0.5 GPa, two Clinozoisite modifications exist, which have compositions of Clinozoisite I ~0.15 to 0.25 Xps and Clinozoisite II >0.55 Xps. The upper thermal stability of Clinozoisite I at 0.5 GPa lies slightly above 600 °C, whereas Fe-rich Clinozoisite II is stable at 650 °C. The schematic phase relations between epidote minerals, grossular-andradite solid solutions and other phases in the system CaO–Al2O3–Fe2O3–SiO2–H2O are shown.
G Dorsam - One of the best experts on this subject based on the ideXlab platform.
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crystal chemistry of synthetic ca2al3si3o12oh sr2al3si3o12oh solid solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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Crystal chemistry of synthetic Ca2Al3Si3O12OH–Sr2Al3Si3O12OH solid-solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
Axel Liebscher - One of the best experts on this subject based on the ideXlab platform.
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crystal chemistry of synthetic ca2al3si3o12oh sr2al3si3o12oh solid solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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Crystal chemistry of synthetic Ca2Al3Si3O12OH–Sr2Al3Si3O12OH solid-solution series of zoisite and Clinozoisite
American Mineralogist, 2007Co-Authors: G Dorsam, Gerhard Franz, Axel Liebscher, Bernd Wunder, Matthias GottschalkAbstract:Coexisting solid-solution series of synthetic zoisite-(Sr) and Clinozoisite-(Sr) were synthesized in a 1 M (Ca,Sr)Cl2 solution at 2.0 GPa, 600 °C for 6 days in a piston cylinder press. Solid solutions were synthesized from XSrZo = Sr/(Ca + Sr) = 0.06 to 1 and XSrCzo = 0.08 to 0.5 in zoisite and Clinozoisite, respectively. The products were characterized with SEM, EMP, and powder-XRD. Zoisites form crystals up to 30 μm in size. Lattice parameters of zoisite increase linearly with increasing Sr content. For synthetic zoisite-(Sr) lattice parameters are a = 16.3567(5) A, b = 5.5992(2) A, c = 10.2612(5) A, and V = 939.78(7) A3 in space group Pnma . Volume of Clinozoisite ( P 21 /m ) increases with increasing XSrCzo , but the lattice parameter a collapses, and b , c , and β have a discontinuity at XSrCzo ≈ 0.25. The decrease in angle β of Clinozoisite results in compression of M3 and T3 polyhedra and increase of the A2 polyhedron. A1-O7 distance of 2.12 A in Clinozoisite is extremely short at XSrCzo ≈ 0.25, but with further Sr incorporation on A2 this distance relaxes quickly to 2.24 A, combined with a torsion of T3. In zoisite, Sr incorporation leads to an opposite movement of neighboring octahedral chains parallel a and causes changes in the linked T3, and angle O5-T3-O6 increases with XSr from 96.3 to 101°. The intra-crystalline distribution of Sr shows that A2 is the favored position and continuous incorporation on A1-position starts above XSrZo ≈ 0.35 for zoisite and above XSrCzo ≈ 0.45 for Clinozoisite.
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Recommended nomenclature of epidote-group minerals
European Journal of Mineralogy, 2006Co-Authors: Thomas Armbruster, Reto Giere, Axel Liebscher, Masahide Akasaka, Paola Bonazzi, Vladimir Bermanec, Christian Chopin, Soraya Heuss-assbichler, Silvio MenchettiAbstract:Epidote-group minerals are monoclinic in symmetry and have topology consistent with space group P21/m and the general formula A2M3(T2O7)(TO4)(O,F)(OH,O). Zoisite is an orthorhombic polymorph of Clinozoisite Ca2Al3(Si2O7)(SiO4)O(OH) and is thus not considered a member of the epidote-group. Epidote-group minerals are divided into three subgroups. (1) Members of the Clinozoisite subgroup are derived from the mineral Clinozoisite Ca2Al3(Si2O7)(SiO4)O(OH) by homovalent substitutions only. The key cation- and anion-sites are A1 = M2+, A2 = M2+, M1 = M3+, M2 = M3+, M3 = M3+, O4 = O2-, O10 = (OH)-. In other words, the dominant valence as listed above must be maintained. (2) Members of the allanite subgroup are REE-rich minerals typified by the eponymous mineral "allanite". This subgroup may be derived from Clinozoisite by homovalent substitutions and one coupled heterovalent substitution of the type A2(REE)3+ + M3M2+ → A2Ca2+ + M3M3+. Thus the valences on the key sites are: A1 = M2+, A2 = M3+, M1 = M3+, M2 = M3+, M3 = M2+, O4 = O2-, O10 = (OH)-. (3) Members of the dollaseite subgroup are REE-rich minerals typified by the eponymous mineral "dollaseite". This subgroup may be derived from Clinozoisite by homovalent substitutions and two coupled heterovalent substitutions of the type A2(REE)3+ + M3M2+ → A2Ca2+ + M3M3+ and M1M2+ + O4F - → M1M3+ + O4O-2. Thus the valences on the key sites are: A1 = M2+, A2 = M3+, M1 = M2+, M2 = M3+, M3 = M2+, O4 = F-, O10 = (OH)-. The key cation-sites M3 and A1 (and, in principle, M2) determine the root name. In both Clinozoisite and allanite subgroups no prefix is added to the root name if M1 = Al. The prefixes ferri, mangani, chromo, and vanado indicate dominant Fe3+, Mn3+, Cr3+, and V3+ on M1, respectively. In the dollaseite subgroup no prefix is added to the root name if M1 = Mg. Otherwise a proper prefix must be attached; the prefixes ferro and mangano indicate dominant Fe2+ and Mn2+ at M1, respectively. The dominant cation on A2 (other than Ca) is treated according to the Extended Levinson suffix designation. This simple nomenclature requires renaming of the following approved species: Niigataite (old) = Clinozoisite-(Sr) (new), hancockite (old) = epidote-(Pb) (new), tweddillite (old) = manganipiemontite-(Sr) (new). Minor modifications are necessary for the following species: Strontiopiemontite (old) = piemon- tite-(Sr) (new), androsite-(La) (old) = manganiandrosite-(La) (new). Before a mineral name can be assigned, the proper subgroup has to be determined. The determination of a proper subgroup is made by the dominating valence at M3, M1, and A2 expressed as M2+ and or M3+, not by a single, dominant ion (i.e., Fe2+, or Mg, or Al). In addition, the dominant valence on O4: X - or X 2- must be ascertained. (M2+)A2 > 0.50, (M3+)M3 > 0.50 → Clinozoisite subgroup, (M3++ M4+)A2 > 0.50, (M2+)M3 > 0.50 → allanite subgroup, {(M2+)M3+M1 - (M3++ M4+)A2 } > 0.50 and (X - )O4 > 0.5 → dollaseite subgroup. Coupled heterovalent substitutions in epidote-group minerals require a special application of the so-called 50 % rule in solid-solution series. (1) Clinozoisite subgroup: The dominant trivalent cation on M3 determines the name, whereas the A2 cation appearing in the suffix has to be selected from among the diva- lent cations. (2) Allanite and dollaseite subgroups: For the sites involved in the charge compensation of a heterovalent substitution in A2 and O4 (i.e. M3 in the allanite subgroup; M3 and M1 in the dollaseite subgroup), identification of the relevant end-member formula must take into account the dominant divalent charge-compensating octahedral cation (M2+) and not the dominant cation
Alison R Pawley - One of the best experts on this subject based on the ideXlab platform.
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volume behavior of hydrous minerals at high pressure and temperature i thermal expansion of lawsonite zoisite Clinozoisite and diaspore
American Mineralogist, 1996Co-Authors: Alison R Pawley, Simon A T Redfern, T J B HollandAbstract:The temperature dependence of the lattice parameters of synthetic lawsonite [CaA12Si207 (OH)2 . H20], natural zoisite [Ca2A13Si30'2 (OH)], natural Clinozoisite [Ca2Al3Si3012(OH)], and synthetic diaspore [AIO(OH)] have been measured at ambient pressure. The volume thermal expansion coefficients for lawsonite, zoisite, and Clinozoisite are approximately constant over the measured temperature ranges (25-590 DCfor lawsonite, 25-750 DCfor zoisite, and 25-900 DCfor Clinozoisite), whereas the thermal expansion of diaspore increases slightly over the range 25-300 DC.Interestingly, the room-temperature volume of Clinozoisite is greater than that of zoisite, but this situation is reversed above -300 DC.The experimental results may be summarized as follows: lawsonite: VI Vo= 1 + 3.16 (:to.05) x 10-5 (T - 298), Vo= 101.51 (:to.Ol) cm3/mol; zoisite: VIVo = 1 + 3.86 (:to.05) x 10-5 (T - 298), Vo= 136.10 (:to.02) cm3/mol; Clinozoisite: VIVo = 1 + 2.94 (:to.05) x 10-5 (T - 298), Vo= 136.42 (:to.05) cm3/mol; diaspore: VIVo = 1 + 7.96 (:to.28) x 10-5 [T - 298 - 20 (VT- ~)], Vo= 17.74 (:to.Ol) cm3/mol.
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volume behavior of hydrous minerals at high pressure and temperature ii compressibilities of lawsonite zoisite Clinozoisite and epidote
American Mineralogist, 1996Co-Authors: T J B Holland, Simon A T Redfern, Alison R PawleyAbstract:The pressure dependence of the lattice parameters of natural zoisite [Ca2A13Si3012(OH)], Clinozoisite [Ca2A13Si30'2(OH)], and epidote [Ca2A12FeSi3012(OH)] as well as synthetic lawsonite [CaAl2Si207(OH)2' H20] have been measured at ambient temperatures by energy-dispersive X-ray diffraction in a diamond-anvil cell. The experimental results for each phase may be summarized concisely in terms ofthe ambient-temperature isothermal bulk modulus K298(using the Murnaghan equation of state and assuming K' = 4): Lawsonite: K298= 191 :t 5 GPa; zoisite: K298= 279 :t 9 GPa; Clinozoisite: K298= 154 :t 6 GPa; epidote: K298= 162 :t4 GPa. These new measurements, together with the new thermal expansion data in the companion paper (Pawley et al. 1996), were used to calculate some phase equilibria for lawsonite dehydration to high pressures for comparison with experimental brackets. Important discrepancies between calculated and experimentally determined reactions become evident above 3 GPa.