The Na-rich and the K-rich Basic Melts of Vulture Volcano, Italy and Their Sources: Evidence from the Melt Inclusion Study in Clinopyroxene from the Haüyne Foidite

This article deals with the results of the study of primary melt inclusions in clinopyroxene megacrysts and phenocrysts from haüyne foidite of SVSl lava flow of the Vulture–San Michele subsyntheme of Vulture Volcano (Italy). The considered rock consists of megacrysts and numerous homogeneous and zoned phenocrysts of clinopyroxene, rare grains of plagioclase, phlogopite, haüyne, analcime, leucite, apatite, magnetite, and glass. The chemical composition of the clinopyroxene corresponds to diopside according to Morimoto classification (1989). The clinopyroxene-hosted melt inclusions are homogenized at 1200–1190°C in megacrysts, and at 1190–1170°C in phenocrysts, and have K-rich and Na-rich basic composition. At relatively close amount of alumina and MgO/(MgO+FeO) ratio, the Na-melt has higher contents of Mg, Ca, Fe, Ti, Mn, Cl and SO3 and lower Ba and water compared to K-melt. Both types of the alkaline basic melts are enriched in incompatible elements, the content of which are over 1–2 orders of magnitude higher than the mantle values, and the Na-melt is more enriched than the K-melt. The high amount of incompatible components in the melts and some HREE depletion relative to LREE indicate an involvement of undepleted mantle in magma generation. The Na-rich and K-rich melts conserved in clinopyroxene-hosted inclusions differ in Ta/Nb, Th/Yb, La/Nb, Y/Nb, Zr/Nb, Ti/Zr, and Ti/Y indicator ratios, which indicates different composition of parental magmas, different mantle sources, and different degrees of their melting. It is concluded that the considered haüyne foidite is formed by mixing of Na-rich and K-rich basic melts, which were derived from different parental magmas and different mantle sources.