. . . "P(LK11202)" . "000310999100002" . . "1"^^ . . "3"^^ . . "Skrzypek, Etienne" . . . . . "Cocherie, A." . . . "6" . . "U\u2013Pb zircon dating, Mineral equilibria, modelling, HP granulite, Zircon petrogenesis, Variscan, Vosges Mountains"@en . . "RIV/00025798:_____/12:00000586" . . "U\u2013Pb zircon dating is combined with petrology, Zr-in-rutile thermometry and mineral equilibria modelling to discuss zircon petrogenesis and the age of metamorphism in three units of the Variscan Vosges Mountains (NE France). The monotonous gneiss unit shows results at 700\u2013500 Ma, but no Variscan ages. The varied gneiss unit preserves ages between 600 and 460 Ma and a Variscan group at 340\u2013335 Ma. Zircon analyses from the felsic granulite unit define a continuous array of ages between 500 and 340 Ma. In varied gneiss samples, zoned garnet includes kyanite and rutile and is surrounded by matrix sillimanite and cordierite. In a pseudosection, it points to peak conditions of *16 kbar/850 C followed by isothermal decompression to 8\u201310 kbar/820\u2013860 C. In felsic granulite samples, the assemblage K-feldspar\u2013 garnet\u2013kyanite\u2013Zr-rich rutile is replaced by sillimanite and Zr-poor rutile. Modelling these assemblages supports minimum conditions of *13 kbar/925 C, and a subsequent P\u2013T decrease to 6.5\u20138.5 kbar/800\u2013820 C. The internal structure and chemistry of zircons, and modelling of zircon dissolution/growth along the inferred P\u2013T paths are used to discuss the significance of the U\u2013Pb ages. In the monotonous unit, inherited zircon ages of 700\u2013500 Ma point to sedimentation during the Late Cambrian, while medium-grade metamorphism did not allow the formation of Variscan zircon domains. In both the varied gneiss and felsic granulite units, zircons with a blurred oscillatoryzoned pattern could reflect solid-state recrystallization of older grains during HT metamorphism, whereas zircons with a dark cathodoluminescence pattern are thought to derive from crystallization of an anatectic melt during cooling at middle pressure conditions. The present work proposes that U\u2013Pb zircon ages of ca. 340 Ma probably reflect the end of a widespread HT metamorphic event at middle crustal level." . . "The origin of zircon and the significance of U\u2013Pb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)" . "157127" . "0010-7999" . . "23"^^ . . "\u0160t\u00EDpsk\u00E1, Pavla" . "Contributions to Mineralogy and Petrology" . "10.1007/s00410-012-0781-1" . "DE - Spolkov\u00E1 republika N\u011Bmecko" . "U\u2013Pb zircon dating is combined with petrology, Zr-in-rutile thermometry and mineral equilibria modelling to discuss zircon petrogenesis and the age of metamorphism in three units of the Variscan Vosges Mountains (NE France). The monotonous gneiss unit shows results at 700\u2013500 Ma, but no Variscan ages. The varied gneiss unit preserves ages between 600 and 460 Ma and a Variscan group at 340\u2013335 Ma. Zircon analyses from the felsic granulite unit define a continuous array of ages between 500 and 340 Ma. In varied gneiss samples, zoned garnet includes kyanite and rutile and is surrounded by matrix sillimanite and cordierite. In a pseudosection, it points to peak conditions of *16 kbar/850 C followed by isothermal decompression to 8\u201310 kbar/820\u2013860 C. In felsic granulite samples, the assemblage K-feldspar\u2013 garnet\u2013kyanite\u2013Zr-rich rutile is replaced by sillimanite and Zr-poor rutile. Modelling these assemblages supports minimum conditions of *13 kbar/925 C, and a subsequent P\u2013T decrease to 6.5\u20138.5 kbar/800\u2013820 C. The internal structure and chemistry of zircons, and modelling of zircon dissolution/growth along the inferred P\u2013T paths are used to discuss the significance of the U\u2013Pb ages. In the monotonous unit, inherited zircon ages of 700\u2013500 Ma point to sedimentation during the Late Cambrian, while medium-grade metamorphism did not allow the formation of Variscan zircon domains. In both the varied gneiss and felsic granulite units, zircons with a blurred oscillatoryzoned pattern could reflect solid-state recrystallization of older grains during HT metamorphism, whereas zircons with a dark cathodoluminescence pattern are thought to derive from crystallization of an anatectic melt during cooling at middle pressure conditions. The present work proposes that U\u2013Pb zircon ages of ca. 340 Ma probably reflect the end of a widespread HT metamorphic event at middle crustal level."@en . "The origin of zircon and the significance of U\u2013Pb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)"@en . "RIV/00025798:_____/12:00000586!RIV13-MSM-00025798" . "The origin of zircon and the significance of U\u2013Pb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)" . . "[2CD859DE9D3D]" . "164" . . "The origin of zircon and the significance of U\u2013Pb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)"@en .