Introduction
Plate dynamics represents a key factor to control lithospheric rifting and by implication, magma generation. “Active” rifting may occur over mantle plumes that influences thermal, rheological and geochemical features of the magma sources (Wilson, 1989; Wilson and Downes, 1991; Wilson and Patterson, 2001; Campbell, 2001; Courtillot et al., 2003). “Passive” rifting may be related to differential stress in the lithosphere often resulting in low volcanicity rifts, mostly along transtensional tectonic systems (Barberi, 1982; Wilson, 1989; Sengor and Natal’in, 2001).
Figure 1. The central Mediterranean area
Tectonomagmatic sketch of the Central Mediterranean with indication of orogenic (red) and anorogenic (blue) volcanic districts. Compressional fronts of Alpine and Apennines/Maghrebian Chains are reported after Carminati and Doglioni (2004). The inferred configuration of the subducted Ionian slab is based on earthquake hypocentres and seismic tomography data (Piromallo and Morelli, 2003).
Extension and rifting close to convergent plate boundaries may be influenced by the mode of subduction, triggering convective instabilities in the upper mantle and allowing inflow of sub-lithospheric components that modify the within-plate magma sources (Wortel and Spakman, 2000; Bianchini et al., 2008; Beccaluva et al., 2010)
In the central Mediterranean the Veneto (Paleogene), Iblei (Neogene-Quaternary) and Sardinia (Neogene-Quaternary) volcanic Provinces represent the major within-plate magmatic events which occurred during the Cenozoic over an area of more than 4,000 km2 (Fig. 1). The Veneto volcanism rests on the Adria microplate, i.e the northern extension of Africa; the Iblei volcanic province (SE Sicily) rests on the African lithosphere, whereas the Sardinia volcanic province rests on a continental block which drifted and rotated during the Oligocene-Miocene away from the paleo-European continental margin.
The overall tectono-magmatic features of these three provinces are typical of intraplate setting, although the volcanic events were close - in space and in time - to orogenic volcanism related to recent subduction zones (Beccaluva et al., 1983; 1987; 1994; 2005a, Alagna et al., this issue; Conticelli et al., this issue; Carminati et al., this issue): 1) the Alpine collisional belt and the Periadriatic orogenic magmatism neighbour the Veneto volcanic district; 2) the Eolian arc magmatism neighbours the Iblean volcanic district; 3) the calcalkaline s.l. orogenic magmatism in Sardinia closely preceded the intraplate volcanism in the same areas.
These occurrences represent particularly convenient case studies to investigate the petrogenesis of intraplate magmas, to evaluate the possible influence of the neighbouring subduction systems and, more in general, to constrain the regional geodynamic control on magmagenesis. In this paper we review the petrological characteristics of intraplate lavas and associated mantle xenoliths from Veneto, Iblei and Sardinia, in order to define the petrological features of primary magmas and their magma sources, the tectono-magmatic significance of these volcanic events and the geodynamic control on the genesis of intraplate magmas.