Amphiboles and clinopyroxenes from Euganean (NE Italy) cumulus enclaves: evidence for subduction related melts below Adria microplate

Euganean Hills are a magmatic district belonging to the Veneto Volcanic Province, whose magmatism developed during an extensional tectonic regime within the Alpine orogenesis in an intra-plate setting (the Adria microplate). Mafic and ultramafic cumulus occur within the Euganean trachytes. We estimated the trace element composition of liquids in equilibrium with cumulus amphiboles and clinopyroxenes, employing a set of partition coefficients. Primary melt compositions were back-calculated assuming an earlier fractional crystallization of olivine and clinopyroxene. These melts are characterized by a marked enrichment in LILE, Th and U relative to N-MORB. Conversely, HREE and HFSE concentrations resemble N-MORB contents. These geochemical signatures are typical of subduction-related magmas, which also characterized the parental melts of Adamello cumulates. Conversely, Veneto Volcanic Province mafic lavas show geochemical patterns typical of anorogenic magmas. Therefore, those rocks are not cogenetic with mafic cumulates, as these rocks are interpreted as crystallized from Alpine subduction-related basaltic magmas, which were subsequently dismembered and transported to shallower levels by ascending lavas related to the Veneto Volcanic Province magmatism. Therefore, magmatic products related to Alpine subduction are, more widespread beneath the Adria microplate than previously known.