ACCRETIONARY HISTORY AND CRUSTAL EVOLUTION OF THE VARISCAN BELT IN WESTERN-EUROPE

The Variscan belt of Western Europe is part of a large intra-Paleozoic belt extending on both sides of the Atlantic from the Ouachitas in the US and the Mauritanides in West Africa to the Bohemian Massif in Czechoslovakia and Poland. The belt was constructed between 500 and 250 Ma as a result of convergence and collision between two main continents, Laurentia-Baltica and Africa, after the closure of various oceanic basins (Iapetus, Rheic and Galicia-Massif Central) now recorded as discrete, in part cryptic, sutures which form the roots of large crystalline nappes in which are found dismembered remnants of oceanic crust and mantle. The accretionary history of the Variscan belt in western Europe is related to the progressive closure of probably two oceanic basins: the Rheic in the north, and another, the Galicia-Massif Central, in the south, by respectively southward and northward intraoceanic subduction followed by obduction and intracontinental lithospheric subduction. The result is a broad (700-800 km), fan-like, divergent belt which must be considered as a classical obduction-collision orogen with a long intracontinental history of about 100-150 Ma. Its arcuate shape is probably due to the northwestward impingement of a promontory of the African continent into Laurentia-Baltica.