Evidence for high-temperature diffusional creep preserved by rapid cooling of lower crust (North Bohemian shear zone, Czech Republic) |
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| Authors: | G Zulauf W Dörr J Fiala J Kotková H Maluski P Valverde-Vaquero |
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| Institution: | Institut für Geologie und Mineralogie, Universität Erlangen, Schlossgarten 5, 91054 Erlangen,;Institut für Geowissenschaften, Universität Gießen, Senckenbergstr. 3, 35390 Gießen, Germany;;Geologickýústav, Akademie Věd ?eske Republiky, 16500 Praha 6, Suchdol,;Czech Geological Survey, 118 21 Praha 1, Czech Republic;;Institut des Sciences de la Terre, de l'Eau et de l'Espace de Montpellier, UniversitéCNRS Montpellier 2, 34095 Montpellier Cedex 05, France;;Geological Survey of Canada, 615 Booth Street, Ottawa A1K 0E9, Ontario, Canada |
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| Abstract: | ABSTRACT Volume diffusion and dislocation creep at T ～ 800 °C led to high finite strain in granulite and orthogneiss of the Oh?e crystalline complex (North Bohemian shear zone). Intragranular creep by volume diffusion is indicated by (i) lobate phase boundaries between feldspar and quartz, and (ii) removal of perthite lamellae and precipitation of tiny, aluminium-rich needles at the margins of K-feldspar. The striking diffusional-creep structures imply high interfacial free energy that has been preserved from equilibration as a result of rapid cooling. U–Pb dating of monazite (342 ± 1 Ma) and 40Ar–39Ar dating of muscovite (341 ± 4 Ma) of Kadaň orthogneiss result in a cooling rate of 50 + 25/?17 °C Myr?1. This high value is attributed to collapse-related 'elevator-style' movements along the North Bohemian shear zone, resulting in the juxtaposition of upper crustal rocks of the Tepla–Barrandian unit against lower crustal rocks of the Erzgebirge crystalline complex. |
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