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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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ca sr fractionation between Zoisite lawsonite and aqueous fluids an experimental study at 2 0 and 4 0 gpa 400 to 800 c
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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Ca-Sr fractionation between Zoisite, lawsonite, and aqueous fluids: An experimental study at 2.0 and 4.0 GPa/400 to 800 °C
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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synthesis of pb Zoisite and pb lawsonite
Neues Jahrbuch Fur Mineralogie-abhandlungen, 2011Co-Authors: G Dorsam, Gerhard Franz, Bernd Wunder, Axel Liebscher, Matthias GottschalkAbstract:Hydrothermal syntheses of Pb-Zoisite Pb2Al3(SiO4|Si2O7|O|OH) and Pb-lawsonite PbAl2(Si2O7|(OH)2)•H2O were per- formed at high pressure and temperature conditions with standard piston cylinder press experiments. Starting materials were mix- tures of PbAl2O4, SiO2, PbO and H2O. The run products were characterized by single-crystal and powder X-ray diffraction, scanning electron microscopy and electron microprobe analyses. Idiomorphic colourless Pb-Zoisite crystals with sizes of 60 × 50 × 120 µm were obtained at 2 GPa and 600 °C, together with Pb- lawsonite and traces of Pb-margarite and plumbotsumite Pb5Si4O8(OH)10. Single-crystal diffraction studies and structure solution of Pb-Zoisite yielded space group Pnma (62), Z = 4, a = 16.4529(7) A, b = 5.6432(2) A, c = 10.3631(5) A, V = 962.18 A 3 , R1 = 0.067. Pb-lawsonite was obtained at 3 GPa/600 °C and at 2 GPa/400 °C. Powder-XRD pattern of Pb-lawsonite shows an orthorhombic unit cell. Peaks at (101), (103), (121), (211), (212), (213), (231), (301), (233) suggest space group Pbnm (62) with Z = 4, a = c 5.85 A, b = 9.03 A, c = 13.31 A, V = 703 A 3 , instead of space group Cmcn for Ca-lawsonite and P21/m for Sr-lawsonite. Group-subgroup relations of the lawsonite structure family are presented.
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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, Bernd Wunder, Axel Liebscher, 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.
Max W. Schmidt - One of the best experts on this subject based on the ideXlab platform.
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Experimental Subsolidus Studies on Epidote Minerals
Reviews in Mineralogy & Geochemistry, 2004Co-Authors: Stefano Poli, Max W. SchmidtAbstract:Despite the fact that epidote group minerals are very typical for metamorphism at very low pressure, e.g., in geothermal fields (Bird and Spieler 2004), the first successful synthesis of Zoisite and epidotess was reported by Coes (1955) in a paper in the Journal of American Ceramic Society entitled “High pressure minerals.” Synthesis conditions were 1 GPa at 800°C; Zoisite was obtained from a mixture of kaolin, SiO2, CaO, and CaCl2, whereas epidote was formed by adding FeCl2•H2O to the previous mixture. Once experimental facilities enabled pressures exceeding a few hundred MPa, Zoisite and epidote minerals were easily obtained from a variety of starting materials, made of oxides, gels and glasses. Historically, early experimental studies on epidote focused on the formation at low pressure conditions, and then ventured into the simple system CaO-Al2O3-SiO2-H2O at conditions attainable by piston cylinder equipment (Newton and Kennedy 1963; Boettcher 1970) in which Zoisite was found to have an extremely large temperature stability. Then, the role of Fe3+ was investigated systematically at pressures typical for the middle and lower continental crust (Holdaway 1972; Liou 1973). Epidote minerals in bulk compositions directly applicable to natural rocks were not investigated experimentally until the early 70’s (Liou et al. 1974; Apted and Liou 1983). Subsequent studies in the context of the very popular hydrous phase stabilities at subduction conditions in the 90’s extended the experimentally determined stability of epidotess in natural compositions to 3.5 GPa. With the relatively easy access to multi-anvil machines, the pressure stability of Zoisite was defined (Poli and Schmidt 1998). The increasing number of experimental studies on epidote minerals reveals that the members of this group of ubiquitous rock forming minerals have …
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the high pressure stability of Zoisite and phase relationships of Zoisite bearing assemblages
Contributions to Mineralogy and Petrology, 1998Co-Authors: S Poli, Max W. SchmidtAbstract:The fluid-absent reaction 12 Zoisite = 3 lawsonite + 7 grossular + 8 kyanite + 1 coesite was experimentally reversed in the model system CaO-Al2O3-SiO2-H2O (CASH) using a multi-anvil apparatus. The upper pressure stability limit for Zoisite was found to extend to 5.0 GPa at 700 °C and to 6.6 GPa at 950 °C. Additional experiments both in the H2O-SiO2-saturated and in the H2O-Al2O3-saturated portions of CASH provide further constraints on high pressure phase relationships of lawsonite, Zoisite, grossular, kyanite, coesite, and an aqueous fluid. Consistency of the present experiments with the H2O-saturated breakdown of lawsonite is demonstrated by thermodynamic analysis using linear programming techniques. Two sets of data consistent with databases of Berman (1988) and Holland and Powell (1990) were retrieved combining experimental phase relationships, calorimetric constraints, and recently measured elastic properties of solid phases. The best fits result in G f ,1,298 ∘,Zoisite=−6,499,400 J and S 1,298 ∘,Zoisite=302 J/K, and G f ,1,298 ∘,lawsonite=−4,514,600 J and S 1,298 ∘,lawsonite=220 J/K for the dataset of Holland and Powell, and G f ,1,298 ∘,Zoisite=−6,492,120 J and S 1,298 ∘,Zoisite=304 J/K, and G f ,1,298 ∘,lawsonite=−4,513,000 J and S 1,298 ∘,lawsonite= 218 J/K for the dataset of Berman. Examples of the usage of Zoisite as a geohygrometer and as a geobarometer in rocks metamorphosed at eclogite facies conditions are worked, profiting from the thermodynamic properties retrieved here.
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H2O transport and release in subduction zones : experimental constraints on basaltic and andesitic systems
Journal of Geophysical Research, 1995Co-Authors: Stefano Poli, Max W. SchmidtAbstract:Phase relationships in natural andesitic and synthetic basaltic systems were experimentally investigated from 2.2 to 7.7 GPa, and 550°C to 950°C, in the presence of an aqueous fluid, in order to determine the stability of hydrous phases in natural subducted crustal material and to constrain reactions resulting in the release of water from subduction zones to the mantle wedge. Water reservoirs in subducted oceanic crust at depths exceeding the amphibole stability field (>70–80 km) are lawsonite (11 wt % H2O), Mg-chloritoid (8 wt %), talc (5 wt %), and Zoisite-clinoZoisite (2 wt %) in basaltic rocks; and lawsonite, Zoisite-clinoZoisite, phengite (4 wt %) and staurolite (2 wt %) in andesitic compositions. The thermal stability of lawsonite at 6.0 GPa extends to ≈800°C and 870°C in basaltic and andesitic compositions, respectively. At pressures above amphibole-out (2.3–2.5 GPa) lawsonite reacts through continuous reactions with steep positive dP/dT slopes to Zoisite-clinoZoisite (until 3.0–3.2 GPa), and at higher pressures (to more than 7.7 GPa) to assemblages containing garnet + clinopyroxene and garnet + clinopyroxene + kyanite in basaltic and andesitic compositions, respectively. On the contrary, the breakdown of Zoisite-clinoZoisite is mainly pressure-sensitive. Phengite represents the hydrous phase with the largest stability field encountered in this study. In andesite, phengite is stable to more than 7.7 GPa and more than 920°C. Talc and staurolite contribute in minor amounts to the water balance in basaltic and andesitic rock compositions. A model for water release from the subducted slab is developed combining thermal models for subduction zones with the experimentally determined phase relationships. Up to 1 wt % and 2 wt % H2O in basaltic and andesitic rocks, respectively, can be stored to depths beyond 200 km in cold subduction zones, mainly by lawsonite and phengite. Dehydration rates are high until amphibole-out, and relatively low at greater depths. The amphibole-out reactions are found to release a significant amount of water in a depth interval of several kilometers, however, they do not represent a discrete pulse of fluid and do not completely dehydrate the descending slab. Fluid release at depths greater than 200 km through phengite and progressive lawsonite breakdown would hydrate the overlying mantle, causing the generation of amphibole or phlogopite peridotite. At higher geothermal gradients, epidote/Zoisite contributes to fluid flux to the mantle wedge at 100–120 km depth. The extensive stability field of phengite may greatly enhance the role of sediments and the small amount of potassium in mafic compositions for the fluid budget in subduction zones at increasing depth.
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the stability of lawsonite and Zoisite at high pressures experiments in cash to 92 kbar and implications for the presence of hydrous phases in subducted lithosphere
Earth and Planetary Science Letters, 1994Co-Authors: Max W. Schmidt, S PoliAbstract:Abstract The breakdown reactions of lawsonite in SiO 2 +H 2 O- and in Al 2 O 3 + H 2 O-saturated synthetic CASH systems were examined between 17 and 92 kbar in both forward and reversed experiments. Lawsonite is stable to 565°C at 20 kbar, 760°C at 40 kbar, and 980°C at 65 kbar. In this pressure range lawsonite breaks down to Zoisite + kyanite + quartz/coesite + H 2 O. An invariant point occurs at 1000°C, 67 kbar. At higher pressures lawsonite breaks down to the assemblage grossular + kyanite + coesite + H 2 O. The steep positive d P /d T > slope of this higher pressure breakdown reaction becomes steeply negative when coesite transforms to stishovite. At 92 kbar, the highest pressure investigated, lawsonite is stable to 1040°C. The invariant point marks also the pressure stability limit of Zoisite since Zoisite reacts to lawsonite + grossular + kyanite + coesite (at temperatures below 1000°C), to grossular + kyanite + coesite + H 2 O (1000–1040°C) and to grossular + kyanite + melt + H 2 O (above 1040°C). These three reactions have a flat Clapeyron slope, and they locate the maximum pressure stability of Zoisite between 65 and 68 kbar (between 800 and 1200°C). Eutectic melting in the SiO 2 + H 2 O-saturated CASH system occurs for the assemblage Zoisite + kyanite + coesite + H 2 O at temperatures approximately 100°C (at 40 kbar) to 40°C (at 65 kbar) higher than the lawsonite breakdown reaction. In the Al 2 O 3 + H 2 O-saturated system the reaction lawsonite+diaspore/corundum=Zoisite+kyanite+H 2 O limits the stability of lawsonite. The diaspore=corundum+H 2 O equilibrium is found to be located about 50°C lower than predicted by previous studies. The equilibrium boundaries of the reactions between 17 and 38 kbar from both SiO 2 + H 2 O- and Al 2 O 3 + H 2 O-saturated chemical systems were used to improve the thermochemical data on lawsonite. Two sets of thermodynamic properties internally consistent with the databases of both Berman [1] and Holland and Powell [2], and also consistent with most previous experimental studies, were calculated employing the technique of linear programming (for Berman's data) and a least-squares fit procedure (for Holland and Powell's data). The unit cell volume of lawsonite was determined (674.67 ± 0.38A 3 ) and G ° formation and S ° third law were fitted. A revised G ° of −4 513 333 J · mol −1 and S ° of 217.45 J · K −1 · mol −1 , and a revised G ° of −4 517 466 J · mol −1 and S ° of 217.06 J · K −1 · mol −1 result, internally consistent with [1] and with [2], respectively. Because lawsonite is stable to 1040°C at 92 kbar, a temperature far higher than predicted by thermal modelling of subduction zones, it is expected to be stable in metabasalts and intermediate compositions (e.g., andesites and greywackes) subducted to depths exceeding 300 km. Lawsonite contains 11 wt% water in its structure, and is thus capable of transporting water deep into the mantle. Its breakdown would contribute significantly to the fluid budget of the slab and overlying mantle wedge. The experimental data in combination with thermal modelling studies indicate that a complete dehydration of the descending oceanic crust is unlikely to occur at shallow levels.
Matthias Gottschalk - One of the best experts on this subject based on the ideXlab platform.
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ca sr fractionation between Zoisite lawsonite and aqueous fluids an experimental study at 2 0 and 4 0 gpa 400 to 800 c
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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Ca-Sr fractionation between Zoisite, lawsonite, and aqueous fluids: An experimental study at 2.0 and 4.0 GPa/400 to 800 °C
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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synthesis of pb Zoisite and pb lawsonite
Neues Jahrbuch Fur Mineralogie-abhandlungen, 2011Co-Authors: G Dorsam, Gerhard Franz, Bernd Wunder, Axel Liebscher, Matthias GottschalkAbstract:Hydrothermal syntheses of Pb-Zoisite Pb2Al3(SiO4|Si2O7|O|OH) and Pb-lawsonite PbAl2(Si2O7|(OH)2)•H2O were per- formed at high pressure and temperature conditions with standard piston cylinder press experiments. Starting materials were mix- tures of PbAl2O4, SiO2, PbO and H2O. The run products were characterized by single-crystal and powder X-ray diffraction, scanning electron microscopy and electron microprobe analyses. Idiomorphic colourless Pb-Zoisite crystals with sizes of 60 × 50 × 120 µm were obtained at 2 GPa and 600 °C, together with Pb- lawsonite and traces of Pb-margarite and plumbotsumite Pb5Si4O8(OH)10. Single-crystal diffraction studies and structure solution of Pb-Zoisite yielded space group Pnma (62), Z = 4, a = 16.4529(7) A, b = 5.6432(2) A, c = 10.3631(5) A, V = 962.18 A 3 , R1 = 0.067. Pb-lawsonite was obtained at 3 GPa/600 °C and at 2 GPa/400 °C. Powder-XRD pattern of Pb-lawsonite shows an orthorhombic unit cell. Peaks at (101), (103), (121), (211), (212), (213), (231), (301), (233) suggest space group Pbnm (62) with Z = 4, a = c 5.85 A, b = 9.03 A, c = 13.31 A, V = 703 A 3 , instead of space group Cmcn for Ca-lawsonite and P21/m for Sr-lawsonite. Group-subgroup relations of the lawsonite structure family are presented.
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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, Bernd Wunder, Axel Liebscher, 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, Bernd Wunder, Axel Liebscher, 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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ca sr fractionation between Zoisite lawsonite and aqueous fluids an experimental study at 2 0 and 4 0 gpa 400 to 800 c
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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Ca-Sr fractionation between Zoisite, lawsonite, and aqueous fluids: An experimental study at 2.0 and 4.0 GPa/400 to 800 °C
American Mineralogist, 2013Co-Authors: Axel Liebscher, Gerhard Franz, G Dorsam, Bernd Wunder, Matthias GottschalkAbstract:The Ca-Sr fractionation between Zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl 2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for Zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients K D (Sr-Ca) A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent Zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are K (Sr-Ca) zo A1-af = 3.38 to 41.08 for the A1 site and K (Sr-Ca) zo A2-af = 0.45 to 6.51 for the A2 site. Assuming γ Ca af = γ Sr af and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca 2+(af) + Sr A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + Ca A1 (M 2+ ) A2 Al 3 [Si 3 O 11 (O/OH)] and Ca 2+(af) + (M 2+ ) A1 Sr A2 Al 3 [Si 3 O 11 (O/OH)] = Sr 2+(af) + (M 2+ ) A1 Ca A2 Al 3 [Si 3 O 11 (O/OH)] yields Δμ 0 = −29 kJ/mol and W Sr-Ca zo A1 = 5.5 kJ/mol for the A1 site and Δμ 0 = −1.1 kJ/mol and W Sr-Ca zo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P 2 1 /m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are K D (Sr-Ca) law Cmcm -af = 1.12 to 11.32 for orthorhombic and K D (Sr-Ca) law P 21 m -af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca 2+(af) + SrAl 2 Si 2 O 7 (OH) 2 ·H 2 O = Sr 2+(af) + CaAl 2 Si 2 O 7 (OH) 2 ·H 2 O assuming γ Ca af = γ Sr af and a symmetric mixing model yields similar values of Δμ 0 = −9 kJ/mol and W Sr-Ca law Cmcm = 10 kJ/mol for orthorhombic and Δμ 0 = −10 kJ/mol and W Sr-Ca law P 21 /m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl 2 aqueous fluids are D Sr zo-af = 2.8 ± 0.7 for Zoisite at 2 GPa/600 °C and D Sr law Cmcm -af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in Zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to Zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the Zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in Zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in Zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, x Sr zo directly reflects x Sr af and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. Zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, Zoisite-bearing thermal regimes of the underlying subduction zone.
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synthesis of pb Zoisite and pb lawsonite
Neues Jahrbuch Fur Mineralogie-abhandlungen, 2011Co-Authors: G Dorsam, Gerhard Franz, Bernd Wunder, Axel Liebscher, Matthias GottschalkAbstract:Hydrothermal syntheses of Pb-Zoisite Pb2Al3(SiO4|Si2O7|O|OH) and Pb-lawsonite PbAl2(Si2O7|(OH)2)•H2O were per- formed at high pressure and temperature conditions with standard piston cylinder press experiments. Starting materials were mix- tures of PbAl2O4, SiO2, PbO and H2O. The run products were characterized by single-crystal and powder X-ray diffraction, scanning electron microscopy and electron microprobe analyses. Idiomorphic colourless Pb-Zoisite crystals with sizes of 60 × 50 × 120 µm were obtained at 2 GPa and 600 °C, together with Pb- lawsonite and traces of Pb-margarite and plumbotsumite Pb5Si4O8(OH)10. Single-crystal diffraction studies and structure solution of Pb-Zoisite yielded space group Pnma (62), Z = 4, a = 16.4529(7) A, b = 5.6432(2) A, c = 10.3631(5) A, V = 962.18 A 3 , R1 = 0.067. Pb-lawsonite was obtained at 3 GPa/600 °C and at 2 GPa/400 °C. Powder-XRD pattern of Pb-lawsonite shows an orthorhombic unit cell. Peaks at (101), (103), (121), (211), (212), (213), (231), (301), (233) suggest space group Pbnm (62) with Z = 4, a = c 5.85 A, b = 9.03 A, c = 13.31 A, V = 703 A 3 , instead of space group Cmcn for Ca-lawsonite and P21/m for Sr-lawsonite. Group-subgroup relations of the lawsonite structure family are presented.
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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, Bernd Wunder, Axel Liebscher, 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, Bernd Wunder, Axel Liebscher, 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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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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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.
