The high-pressure Iberian-Czech belt in the Variscan orogen: Extrusion into the upper (Gondwanan) plate?

A Siluro-Devonian. high-pressure (HP) belt (the Iberian-Czech or IC belt) extends from Ibena (Cordoba-Coimbra Shear Zone) through Armorica and the Massif Central to the Bohemian Massif (Iberian-Czech [IC] belt), and includes arc and periarc rocks, MORB and supra-subduction ophiolites, and passive margin sequences It has generally been interpreted to be either (a) a suture of the Galician, South Brittany, Massif Central and Moldanubian ocean: (b) a nappe rooted to the north in the Rheic Ocean, or(c) the result of post-collisional strike-slip shuffling of the Gondwanan margin during which a slice of the Rheic Ocean was inserted into the Gondwanan margin We agree with a Rheic Ocean origin, but propose that the IC belt represents a pre-collisional part of the Gondwanan continental-oceanic margin that was removed by subduction erosion, underwent HP metamorphism, and was then extruded into the overlying Gondwanan plate This model explains (i) the lack of paleolatitudinal and faunal differences across the IC belt, (ii) the juxtaposition of active margin tectonics within synchronous passive margin sequences, and (iii) the pre-collisional age of most of the HP metamorphism. The complete range of HP rocks in the IC belt, from blueschist to hot eclogites, indicates that previous correlations with B- and A-type subduction, respectively, cannot be sustained (C) 2009 International Association for Gondwana Research Published by Elsevier B.V All rights reserved