aus:
Raumer, J.F.. v., Stampfli, G.M. ] Bussy. B. (2003): Gondwana-derived microcontinents? The constituents of the Variscan and Alpine collisional orogens.- Tectonophysics 365 (2003) 7-22
von www.elsevier.com/locate/tecto
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Fig. 4. Schematic representation of drift history of Gondwananderived basement areas from the Silurian to the Carboniferous, with representation of the oceanic domains, modified from Stampfli et al. (2002, with more details therein). 440 Ma?Indication of intervening main oceanic plates. Avalonia and its satellites (Malapolska, Lysogory, Brunovistulikum, see Belka et al., 2002) are already amalgamated with Laurussia. Subduction at the Gondwana margin continued in the former more eastern located domains. The dashed line indicates location of the future opening of Palaeo-Tethys. 420 Ma?An archipelago-like ribbon-continent separated from Gondwana (European Hunic Terranes) during opening of Palaeo-Tethys along the Gondwana margin. Its opening is interpreted as back-arc spreading related to Gondwana-directed subduction of Rheic/Proto-Tethys. 380 Ma?Early collision of Gondwana-derived European Hunic Terranes with Laurussia-derived terranes. 340 Ma?Major collision and closure of Rhenohercynian domain.
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Abstract
The European Variscan and Alpine mountain chains are collisional orogens, and are built up of pre-Variscan ‘‘building blocks’’ which, in most cases, originated at the Gondwana margin. Such pre-Variscan elements were part of a pre-Ordovician archipelago-like continental ribbon in the former eastern prolongation of Avalonia, and their present-day distribution resulted from juxtaposition through Variscan and/or Alpine tectonic evolution. The well-known nomenclatures applied to these mountain chains are the mirror of Variscan resp. Alpine organization. It is the aim of this paper to present a terminology taking into account their pre-Variscan evolution at the Gondwana margin. They may contain relics of volcanic islands with pieces of Cadomian crust, relics of volcanic arc settings, and accretionary wedges, which were separated from Gondwana by initial stages of Rheic ocean opening. After a short-lived Ordovician orogenic event and amalgamation of these elements at the Gondwanan margin, the still continuing Gondwana-directed subduction triggered the formation of Ordovician Al-rich granitoids and the latest Ordovician opening of Palaeo-Tethys. An example from the Alps (External Massifs) illustrates the gradual reworking of Gondwana-derived, pre-Variscan elements during the Variscan and Alpine/ Tertiary orogenic cycles.
Keywords: Gondwana-derived terranes; Plate-tectonic terminology; Polymetamorphic basement relics; Collisional orogens; Alpine; Variscan
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