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- Structure and metamorphism in the Seve-Köli nappe complex (Scandinavian Caledonides) and its implications concerning the formation of metamorphic nappes
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Structure and metamorphism in the Seve-Köli nappe complex (Scandinavian Caledonides) and its implications concerning the formation of metamorphic nappes
Abstract
The stratigraphy and structure of the Seve-Köli nappe complex is described. Four units have been distinguished based on lithologic, metamorphic and structural criteria. They are usually separated by mylonite zones. Structurally from top to bottom an increase in metamorphic grade from greenschist facies to upper amphibolite facies, and then a decrease to green schist facies is found in the Seve nappe. This inversion of metamorphic zonation is due to thrusting. Based on microstructural evidence it can be shown that the acme of metamorphism predates the formation of the nappes, which is related to a second folding phase.
The mechanism of nappe formation is considered to be inhomogeneous shear with maximum strain in the mylonite zones.
The cause of the relatively high pressure metamorphism is thought to be burial in a first folding phase, possibly in a subduction zone, whereas metamorphism ceased when the rocks were upthrusted to the surface during the formation of the nappes.