High pressure alpine metamorphism of the Pelagonian allochthon in the Kastania area (Southern Vermion), Greece

Abstract

The Pelagonian allochthon in the Kastania area (Southern Vermion) consists of pre-alpine and alpine rocks that underwent two episodes of Alpine HP/LT metamorphism. The first episode, of Lower Cretaceous age, is represented by the mineral assemblages: Quartz-albite-microcline-phengite±garnet-clinozoisite± biotite±rutiletitanite in orthogneisses and the Kastania metagranite and garnet-chloritoid-chlorite±kyanite-white K-micaparagonite- rutile in high alumina metapelites. Pressures, were estimated at TO kbar at 500 °C, applying the phengite geobarometry and more than 22 Kbar, calculating the reaction Grt+Rt+Qtz+W®Ttn-l-Czo, occurred in the Kastania metagranite during decompression. Recrystallization at albite-epidote-amphibolite facies conditions accompanied by penetrative deformation defines the dominant mineral assemblages and textures in orthogneisses, metapelites and metabasites. The second metamorphic episode of a probable Eocene age occurred under blueschist/greenschist facies conditions and produced fine-grained phengite, stilpnomelane, green biotite and blue amphibole in orthogneisses and amphibolites.