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Tectonics 31 (2012) TC1013
Crustal influx, indentation, ductile thinning and gravity redistribution in a continental wedge: Building a Moldanubian mantled gneiss dome with underthrust Saxothuringian material (European Variscan belt)
F. Chopin 1, 2, K. Schulmann 2, 3, E. Skrzypek 2, J. Lehmann 2, 4, J.R. Dujardin 3, J.-E. Martelat 5, O. Lexa 4, 6, M. Corsini 1, J.B. Edel 2, P. Štipska 2, Pavel Pitra 7

[1] The contribution of lateral forces, vertical load, gravity redistribution and erosion to the origin of mantled gneiss domes in internal zones of orogens remains debated. In the Orlica-Snieznik dome (Moldanubian zone, European Variscan belt), the polyphase tectono-metamorphic history is initially characterized by the development of subhorizontal fabrics associated with medium- to high-grade metamorphic conditions in different levels of the crust. It reflects the eastward influx of a Saxothuringian-type passive margin sequence below a Teplá-Barrandian upper plate. The ongoing influx of continental crust creates a thick felsic orogenic root with HP rocks and migmatitic orthogneiss. The orogenic wedge is subsequently indented by the eastern Brunia microcontinent producing a multiscale folding of the orogenic infrastructure. The resulting kilometre-scale folding is associated with the variable burial of the middle crust in synforms and the exhumation of the lower crust in antiforms. These localized vertical exchanges of material and heat are coeval with a larger crustal-scale folding of the whole infrastructure generating a general uplift of the dome. It is exemplified by increasing metamorphic conditions and younging of 40Ar/39Ar cooling ages toward the extruded migmatitic subdomes cored by HP rocks. The vertical growth of the dome induces exhumation by pure shear-dominated ductile thinning laterally evolving to non-coaxial detachment faulting, while erosion feeds the surrounding sedimentary basins. Modeling of the Bouguer anomaly grid is compatible with crustal-scale mass transfers between a dense superstructure and a lighter infrastructure. The model implies that the Moldanubian Orlica-Snieznik mantled gneiss dome derives from polyphase recycling of Saxothuringian material.
1 :  Géoazur (GEOAZUR)
Université Nice Sophia Antipolis (UNS) – CNRS : UMR7329 – Institut de recherche pour le développement [IRD] – Observatoire de la Côte d'Azur – INSU – Université Pierre et Marie Curie (UPMC) - Paris VI
2 :  Ecole et Observatoire des sciences de la terre de Strasbourg (EOSTS)
INSU – CNRS : UMS830 – Université de Strasbourg
3 :  Institut de physique du globe de Strasbourg (IPGS)
CNRS : UMR7516 – INSU – Université de Strasbourg
4 :  Czech Geological Survey
Czech Geological Survey
5 :  Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE)
CNRS : UMR5276 – INSU – Université Claude Bernard - Lyon I (UCBL) – École Normale Supérieure (ENS) - Lyon
6 :  Institute of Petrology and Structural geology
Charles University in Prague (CZECH REPUBLIC)
7 :  Géosciences Rennes (GR)
CNRS : UMR6118 – INSU – Observatoire des Sciences de l'Univers de Rennes – Université de Rennes 1
Terre, Temps, traçage
Planète et Univers/Sciences de la Terre
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