Variscan basic dykes in the Pelagonian (Northern Greece and south FYROM): Geodynamic significance based on petrological, geochemical and geochronological studies

Abstract

Dolerite dykes intruding Variscan plutonites were studied in terms of mineralogy, petrology, geochemistry and geochronology. The main mineral constituents were studied and the sequence of crystallization has been derived. The geochemical characteristic indicate mantle origin of the dolerites and magma sources different from the hosting granitoids. From SHRIMP analyses of five spots on four different zircon crystals, resulted a 292.0±4.1 Ma age that is interpreted as the time of crystallization of the dolerite. The hosting granitoids are probably the result of mixing between two possible end-members: enriched mantle and acid metaigneous or lower crustal metasediments. The Variscan age of the dolerites, in combination with the geochemical characteristics, indicated that the enriched mantle basaltic material should be the source of the dolerite veins. These mantle-derived basaltic melts may represent the underplated material, which probably provided the necessary thermal input to the dehydration melting in the lower crust. The dolerites should have intruded the newly formed batholiths before or at the first stages of their uplift, recording the last events of the Variscan subduction.