Un modèle géodynamique des Calédonides scandinaves centro-méridionales de Norvège

A new model for the Scandinavian Caledonides is presented: two oceanic basins, opened during Cambrian times, closed during Ordovician-Silurian times are represented within the internal nappes. The Baltic Shield and its covers are involved in the cratonic sheets and External Nappes. The major play of the Precambrian basements and covers thrusted in the Scandinavian belt (The western Norwegian basement to the west, the cratonic sheets to the east) is emphazised. The geochemical investigation indicates the presence of an evaporitic trend in the epicontinental meta-sediments of the Gula complex, and the Komatiitic character of the associated meta-volcanics. The Trondhjemites genesis is considered along with the syn-orogenic evolution of Tholeiitic igneous complexes. The nappes-built up of the Trondheim complex is synchronous of the Barrovian metamorphic stage and the major features of the ductile deformation (transversal stretching lineation, pinch and swell structures, plastic deformation of Hornblende). The late emplacement of the whole Trondheim nappe complex (gravity gliding) occurs during large dextral wrenching in response to the oblique continental collision. Geodynamic relationships among the North Atlantic Caledonian branches (Greenland, Scandinavia, British Isles, Mid-Europa) are outlined and presented on palaeogeographic maps constructed for the four major episodes of the Caledonian orogeny (Cambro-Tremadoc; Arenig-Llandvirn ; Caradoc-Asghill ; Ludlow-lower Devonian).