Volcanism and Plutonism in the Caledonides of Scandinavia

Abstract

Caledonian igneous rocks are concentrated in the upper part of the Middle Allochthon and in the higher nappes. Within these tectonically bounded stratigraphic packages there are preserved relics of pre-Iapetus rifting, lapetus opening with oceanic crust, lapetus closing with subduction-related arc volcanics and even late extentional magmatism developed on newly sutured crust. Different environments are characteristic of successively higher groups of nappes:-l) Rifting related dolerites and amphibolites occur in the Middle (Särv Nappe and equivalents) and Upper (Seve Nappes and equivalents) Allochthons respectively, intruded or extruded in an ensialic environment. 2) Arc-related (probably ensimatic) volcanic and sub-volcanic rocks occur within the Upper Allochthon (Köli Nappes and equivalents). 3) Fragmentary ophiolite slices and associated within-plate basalts occur in the Upper Allochthon (including the Staren Nappe) and possibly even the Uppermost Allochthon.