Mantle Derived and Crustal Melts Dichotomy in Northern Greece: Spatiotemporal and Geodynamic Implications

Two distinct groups of subduction-related (orogenic) granitoid rocks, one Jurassic and the other Tertiary, occur in the area between the Vardar (Axios) Zone and the Rhodope Massif in northern Greece. The two groups of granitoids differ in many respects. The first group shows evolved geochemical characters, it is not associated with mafic facies, and evidence of magmatic interaction between mantle- and crustal-derived melts is lacking. The second group has less evolved geochemical characters, it is associated with larger amount of mafic facies, and magmatic interaction processes between mantle-derived and crustal melts are ubiquitous as evidenced by mafic microgranular enclaves and synplutonic dykes showing different enrichment in K2O, Ti, and incompatible elements. This kind of magmatism can be attributed to the complex geodynamic evolution of the area. In particular, we suggest that two successive subduction events related to the closure of the Vardar and the Pindos oceans, respectively, occurred in the investigated area from Late Jurassic to Tertiary. We relate the genesis of Jurassic granitoids to the first subduction event, whereas Tertiary granitoids are associated with the second subduction. Fluids released by the two subducted slabs induced metasomatic processes generating a leopard skin mantle wedge able to produce mafic melts ranging from typical calc-alkaline to ultra-potassic. Such melts interacted in various amounts with crustal calc-alkaline anatectic melts to generate the wide spectrum of Tertiary granitoids occurring in the study area.