Origin and geodynamic significance of Tertiary postcollisional basaltic magmatism in Serbia (central Balkan Peninsula)

Tertiary basaltic magmatism in Serbia occurred through three episodes: (i) Paleocene/Eocene, when mostly east Serbian mafic alkaline rocks (ESPEMAR) formed, (ii) Oligocene/Miocene, dominated by high-K calc–alkaline basalts, shoshonites (HKCA–SHO) and ultrapotassic (UP) rocks, and (iii) Pliocene episode when rocks similar to (ii) originated. In this study, the geodynamics inferred from petrogenesis of the (i) and (ii) episodes are discussed. The ESPEMAR (62–39 Ma) occur mainly as mantle xenolith-bearing basanites. Their geochemical features, such as the REE patterns, elevated HFSE contents and depleted Sr–Nd isotope signatures, indicate a relatively small degree of melting of an isotopically depleted mantle source. Their mantle-normalized trace element patterns are flat to concave and “bell-shaped”, characteristic of an OIB source free of subduction component. 87Sr/86Sri and 143Nd/144Ndi isotope ratios (0.7030–0.7047 and 0.5127–0.5129, respectively) indicate a depleted source for the ESPEMAR similar to the European Asthenospheric Reservoir (EAR). The HKCA–SHO rocks (30–21 Ma) occur as basalts, basaltic andesites and trachyandesites. They show enrichment in LILE and depletion in HFSE with all the distinctive features of calc–alkaline arc-type magmatism. This is coupled with somewhat enriched Sr–Nd isotope signature (87Sr/86Sri=0.7047–0.7064, 143Nd/144Ndi=0.5124–0.5126). All these features are characteristic of subduction-related metasomatism and fluxing of the HKCA–SHO mantle source with fluids/melts released from subducted sedimentary material.