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Introduction: Zircon is a chemically inert mineral that can survive the processes of weathering, ... more Introduction: Zircon is a chemically inert mineral that can survive the processes of weathering, transportation, diagenesis, metamorphism and even crustal melting. Magmatic zircons incorporate minor and trace amounts of geochemically important lithophile elements such as Sc, Y, the rare earth elements (REE), Ti, Hf, Th, U, Nb, Ta, V, and P [1, 2]. Therefore, zircon/melt partition coefficients (D values) of these elements can be used to estimate the trace element composition of the magma from which zircon crystallized. Such information is of particular interest to geochemist and petrologist who study the chemical composition and evolution of the Earth's crust [2]. For example, D values have been applied to Eoarchean detrital zircons to determine whether the trace element composition of the coexisting magma was tonalitic, granitic or mafic [3-6].
... is shared by both groups and consists of phyllites, andalusite-cordierite mica schists, staur... more ... is shared by both groups and consists of phyllites, andalusite-cordierite mica schists, staurolitemica schists and sillimanite mica schists, with ... 5) from the Langzishan Formation and the Dashiqiao Formation of the North Liaohe Group have been investigated recently (Luo et al ...
Field evidence and thermodynamic data at ambient conditions suggest that complexing of Zr with hy... more Field evidence and thermodynamic data at ambient conditions suggest that complexing of Zr with hydroxyl ions at high pH enhances the solubility of zircon. We tested this hypothesis by measuring the solubilities of the assemblages zircon (ZrSiO4) + baddeleyite (Z + B) and zircon + quartz (Z + Q) in neutral to alkaline fluids at 0.2 GPa and 450–750 °C. In neutral to alkaline fluids (0, 0.1, 1m NaOH) zircon dissolved incongruently in quartz-undersaturated fluids to form baddeleyite. At 450 °C various Na–Zr–silicates precipitated from fluids saturated and undersaturated in quartz. We observed no significant dependence of solubility on temperature. The measured solubilities of zircon in pure H 2 O at 600 and 750 °C are only slightly higher than the procedural blank of 3.3 Â 10 À7 m Zr. However, the measured solubility of zircon increases with increasing aqueous silica, suggesting that zirconium complexes with silica in the fluid. At 600 °C linear regression of experimental results yielded: ln (Zr) = 0.25 + 2.9*ln(Si) where terms in parentheses represent molal concentrations. Zircon solubility also seems to increase with increasing hydroxyl concentration in the fluid. Enhanced solubility in silica-rich, alkaline fluids may cause dissolution–reprecipitation of zircon and resetting of its isotopic clocks, suggesting that some zircon U–Pb ages may correspond to fluid events.
Introduction: Zircon is a chemically inert mineral that can survive the processes of weathering, ... more Introduction: Zircon is a chemically inert mineral that can survive the processes of weathering, transportation, diagenesis, metamorphism and even crustal melting. Magmatic zircons incorporate minor and trace amounts of geochemically important lithophile elements such as Sc, Y, the rare earth elements (REE), Ti, Hf, Th, U, Nb, Ta, V, and P [1, 2]. Therefore, zircon/melt partition coefficients (D values) of these elements can be used to estimate the trace element composition of the magma from which zircon crystallized. Such information is of particular interest to geochemist and petrologist who study the chemical composition and evolution of the Earth's crust [2]. For example, D values have been applied to Eoarchean detrital zircons to determine whether the trace element composition of the coexisting magma was tonalitic, granitic or mafic [3-6].
... is shared by both groups and consists of phyllites, andalusite-cordierite mica schists, staur... more ... is shared by both groups and consists of phyllites, andalusite-cordierite mica schists, staurolitemica schists and sillimanite mica schists, with ... 5) from the Langzishan Formation and the Dashiqiao Formation of the North Liaohe Group have been investigated recently (Luo et al ...
Field evidence and thermodynamic data at ambient conditions suggest that complexing of Zr with hy... more Field evidence and thermodynamic data at ambient conditions suggest that complexing of Zr with hydroxyl ions at high pH enhances the solubility of zircon. We tested this hypothesis by measuring the solubilities of the assemblages zircon (ZrSiO4) + baddeleyite (Z + B) and zircon + quartz (Z + Q) in neutral to alkaline fluids at 0.2 GPa and 450–750 °C. In neutral to alkaline fluids (0, 0.1, 1m NaOH) zircon dissolved incongruently in quartz-undersaturated fluids to form baddeleyite. At 450 °C various Na–Zr–silicates precipitated from fluids saturated and undersaturated in quartz. We observed no significant dependence of solubility on temperature. The measured solubilities of zircon in pure H 2 O at 600 and 750 °C are only slightly higher than the procedural blank of 3.3 Â 10 À7 m Zr. However, the measured solubility of zircon increases with increasing aqueous silica, suggesting that zirconium complexes with silica in the fluid. At 600 °C linear regression of experimental results yielded: ln (Zr) = 0.25 + 2.9*ln(Si) where terms in parentheses represent molal concentrations. Zircon solubility also seems to increase with increasing hydroxyl concentration in the fluid. Enhanced solubility in silica-rich, alkaline fluids may cause dissolution–reprecipitation of zircon and resetting of its isotopic clocks, suggesting that some zircon U–Pb ages may correspond to fluid events.