The Mylonite Zone in south-western Sweden (Värmland) A re-interpretation

Abstract

The Värmland part of the Mylonite Zone in western Sweden and the surrounding rocks to the west of Lake Fryken have been mapped, in order to study the origin of this lithotectonic complex. The area is predominantly made up of acid-to-intermediate gneisses, most of which are presumably of plutonio origin. The rocks of the Mylonite Zone are commonly intensely deformed. Several periods of deformation have been distinguished. The spatial distribution of petrographically similar rocks indicates that the Mylonite Zone predominantly comprises rocks of the north-eastern Pregothian mega-unit. Rocks of the southwestern Pregothian mega-unit are found in the south-eastern part of the investigated section of the Mylonite Zone. The formation of the Mylonite Zone is later than the folding of the Pregothian rocks, and possibly also later than the intrusion of the hyperites.