GEOCHEMISTRY AND PETROGENESIS OF THE EARLY CRETACEOUS CONTINENTAL RIFT-TYPE VOLCANIC-ROCKS OF THE MECSEK MOUNTAINS, SOUTH HUNGARY

Early Cretaceous volcanic rocks (basanite to phonolite) from the Mecse k Mountains (South Hungary) represent the products of Late Mesozoic ex tension-related alkaline magmatism at the southern margin of the Europ ean plate. Two mafic groups have been distinguished: ankaramite-alkali basalt and Na-basanite-phonotephrite. Phonolites could have been form ed from the Na-basanitic magma by low-pressure fractionation. The majo r and trace element characteristics of the Mecsek basalts are similar to those of alkaline basalts of other intraplate areas and have a St. Helena-type OIB affinity. The mantle source of the Mecsek volcanics co uld be similar to that proposed by Wilson and Downes (1991) as one of the mantle endmembers for extension-related Tertiary-Quaternary alkali ne basalts in Europe. Geochemical modelling indicates that the primary magmas of the Na-basanite series were formed by about 4% partial melt ing, whereas ankaramites and alkali basalts originated by about 6% par tial melting of a garnet-peridotite source.