New geochemical and geochronological data on the Cenozoic Veneto Volcanic Province: Geodynamic inferences

Abstract

The Veneto Volcanic Province (VVP; NE Italy) is an intraplate magmatic area whose activity occurred intermittently in the Cenozoic, generating five districts (Val d'Adige, Lessini Mts., Marostica Hills, Berici Hills, and Euganean Hills). This intraplate magmatism was concomitant to the collision of the European plate and Adria microplate and the orogenesis of the neighboring Alpine belt. Different geodynamic models suggested relationships between VVP and the coexisting subduction processes. To give new insights on this on-going debate, this work provides new petrographic and geochemical data, including Sr-Nd-Pb isotopic and 40Ar/39Ar and KAr geochronological analyses for lavas sampled in the Lessini Mts. and Val d'Adige, which are the oldest VVP magmatic districts, as well as Marostica Hills and Berici Hills, which are the least investigated districts. The trace element distribution indicates that VVP melts were variously affected by metasomatic enrichments stabilized as phlogopite and/or amphibole. The Sr-Nd-Pb isotope ratios conform to the dominant features of sub-lithospheric mantle components widespread at regional scale throughout the whole European and Mediterranean area. Within this framework, the geochronological data indicate that the oldest magmatic episodes occurred in the Eocene (45–42 Ma) in the Lessini Mts. and Val d'Adige, simultaneously with the orogenic magmatism of Adamello intrusive complex along the Giudicarie Fault, a portion of the Periadriatic lineament which is an important Alpine suture. In our geodynamic reconstruction we propose that the Giudicarie Fault is the superficial expression of a slab tear, responsible for the uprising of an asthenospheric poloidal mantle flow, which induced both the Adamello and VVP magmatism. Subsequently, VVP activity migrated eastwards following the general mantle flow as indicated by minor volcanic pulses in the Euganean and Marostica Hills during Oligocene and Miocene.