The tectonometamorphic evolution of a garnet peridotite lens, N. Jämtland, Sweden

Abstract

The Friningen Peridotite Lens, found in N. Jämtland, Central Sweden is a tectonically emplaced garnet peridotite lens located in the Seve Nappe Complex (SNC) of the Scandinavian Caledonides. The peridotite records older protolith mineral assemblages than the host gneisses and is crosscut by a basic garnet pyroxenite dike. Metamorphism in the SNC due to an early Caledonian event is dated at 500 ± 50 Ma. Microstructural analyses indicate the proposed collision of the Virisen island arc cannot be responsible for this event as the garnet peridotite originates from Sub-Continental lithospheric mantle. The most likely conceptual model for the origin of the SNC is a collision of Baltica with an unknown microcontinent. Geochemical analyses of the dike indicate extensive metasomatism during the residence time of the peridotite lens in the mantle wedge. Micro- and mesostructural evidence indicates the dike behaves as a low viscosity layer during deformation.