Devonian–Permian magmatic pulses in the northern Vosges Mountains (NE France): result of continuous subduction of the Rhenohercynian Ocean and Avalonian passive margin
Published:January 01, 2014
Anne-Sophie Tabaud, Hubert Whitechurch, Philippe Rossi, Karel Schulmann, Catherine Guerrot, Alain Cocherie, 2014. "Devonian–Permian magmatic pulses in the northern Vosges Mountains (NE France): result of continuous subduction of the Rhenohercynian Ocean and Avalonian passive margin", The Variscan Orogeny: Extent, Timescale and the Formation of the European Crust, K. Schulmann, J. R. Martínez Catalán, J. M. Lardeaux, V. Janoušek, G. Oggiano
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Middle Devonian–Permian magmatic rocks from the northern Vosges Mountains show temporal and chemical variations which are linked to the continuous subduction of the Rhenohercynian oceanic crust and the Avalonian Devonian passive margin underneath the Saxothuringian continental crust. Major and trace elements and Sr–Nd isotopes of the northern Vosges basic to acidic magmatic rocks show that they evolved through time from: (1) Middle Devonian tholeiitic to calc-alkaline volcanic Rabodeau–Schirmeck sequence derived from partial melting of a depleted mantle, with these primary magmas having triggered anatexis of young crustal material of the Saxothuringian crust; (2) calc-alkaline Bande Médiane volcanic belt (c. 334 Ma), diorite and Hohwald granodiorite intrusion (c. 329 Ma) originated from enriched mantle contaminated and metasomatized by fluids expelled from a subduction zone; (3) high-K calc-alkaline Belmont granite (c. 318 Ma), whose chemical signature suggests magma-mixing between enriched mantle-derived melts and magmas from a young crustal source; (4) Mg–K Younger granite (c. 312 Ma) might be related to partial melting of enriched mantle which interacted with juvenile crustal material; and (5) Kagenfels S-type granite and Permian volcanic rocks generated by anatexis of meta-igneous and minor metasedimentary rocks.
Chemical analyses of biotite and amphibole of the northern Vosges rocks are available at http://www.geolsoc.org.uk/SUP18740.
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The Variscan Orogeny: Extent, Timescale and the Formation of the European Crust
This volume summarizes the state of the art of Variscan geology from Iberia to the Bohemian Massif. The European Variscan belt consists of two orogens: the older, northern and the younger, southern. The northern Variscan realm was dominated by Late Devonian–Carboniferous rifting, subduction and collisional events as defined by sedimentary records, crustal growth, recycling of continental crust and large-scale deformations. In contrast, the southern European crust was reworked by major Late Carboniferous collision followed by Permian wrenching. The Late Carboniferous–Permian orogeny overprinted the previously accreted system in the north, but with much lower intensity, resulting in magmatic recycling and extensional tectonics.
These two main orogenic cycles do not reflect episodic evolution of a single orogenic system but a complete change in orientation of stress field, thermal regime, degree of reworking and recycling of European crust, reflecting a major switch in plate configurations at the Early–Late Carboniferous boundary.