Sicily Magmatic Province

The Sicily Province consists of several young to active volcanoes occurring in eastern Sicily, in the Sicily Channel and in the southern Tyrrhenian Sea. Etna is by far the best known among these volcanoes; other centres include Iblei, Pantelleria, Linosa, several seamounts in the Sicily Channel, the Island of Ustica and the Prometeo submarine lava field in the southern Tyrrhenian Sea.


Location map of Sicily volcanoes. (Peccerillo, 2005).

The Sicily volcanoes are located in a variety of structural settings and on different types of bedrocks. Mount Etna (about 0.6 Ma to present) occurs on the accretionary prism of the Africa-Europe subducting system, at the contact between the Ionian lithosphere, the northern margin of the African plate and the corrugated Sicilian-Maghrebian chain. The Iblei volcanoes (about 7-1.5 Ma) are sited on the Iblean Plateau, an area of the Pelagian Block which has been intermittently affected by volcanism since Triassic times. Plio-Quaternary volcanism developed along NE-SW trending faults at graben margins cutting Oligocene to Miocene platform carbonates and foredeep sequences.

The volcanoes of the Sicily Channel (Linosa and Pantelleria and a number of seamounts; Miocene to present in age) are mainly located along ex tensional NW-SE trending faults bordering the continental rift systems that affected the northern African continental lithosphere or along N-S strikeslip faults. Three main rift zones are recognized in the Sicily channel: the Malta, Linosa and Pantelleria grabens. The processes that generated rifting in this zone are not fully understood.

The Ustica island (0.75-0.13 Ma) occurs in the southern Tyrrhenian Sea, west of the Aeolian volcanic arc, along the southern margin of the Tyrrhenian abyssal plain, probably at the intersection between E-W and NW-SE trending faults. The recently discovered Prometeo submarine lava field is located a few km southeast of Ustica.


The mafic rocks of the Sicily Province range from silica oversaturated quartz tholeiites to undersaturated nephelinites , which display variable enrichment in incompatible elements and radiogenic isotopes. At Etna there is an apparent increase in alkalinity with time, from early tholeiites to late alkali basalts and hawaiites, although tholeiitic to Na-alkaline compositions coexist as melt inclusions in mineral phases of single rocks, demonstrating the contemporaneous production of the two types of magmas. At Iblei, mafic rocks show a wider compositional range from quartz-tholeiites to nephelinites. At Pantelleria, Linosa and Ustica the mafic rocks are mostly transitional to Na-alkaline, ranging from hyperstene- to nepheline-normative.

There is a general agreement that the variable petrochemical affinity, degree of silica saturation and incompatible element enrichment of mafic rocks in Sicily are the effect of the variation in the degrees of partial melting, depth of magma generation and intensity of source metasomatism within the upper mantle, However, the variable isotopic signatures found in the mafic rocks, both at local and regional scales, require that sources were compositionally heterogeneous. In general, tholeiitic rocks have more primitive (less radiogenic Sr and more radiogenic Nd) isotopic compositions than alkaline rocks, suggesting a lower degree of incompatible element enrichment for their sources.

Major and trace element geochemistry of melt inclusions indicate that the primary alkaline and tholeiitic magmas at Etna had compositions much more mafic than the outcropping rocks. They were also more compositionally variable, indicating that a large range of primitive magmas were formed. Geochemical modelling has shown that magmas parental to the alkaline suite were generated by less than 5% of mantle melting, whereas primary tholeiitic magmas were formed by much more extensive mantle melting of about 15-20%. Armienti et al. (2004) indicated a pressure of 1.5-1.8 GPa for the last equilibration within the upper mantle for the parental magmas of Etna rocks. This represents a minimum depth of partial melting, and Corsaro and Cristofolini (1996) and Corsaro and Pompilio (2004) suggest derivation of alkaline magmatism from somewhat deeper sources (1.5 to 3.0 GPa), within the stability field of garnet lherzolite.

The Island of Ustica and the nearby Prometeo lava field have been less extensively studied than Etna. However, the available data have shown close compositional similarities among these volcanoes. Cinque et al. 1988) found that the Ustica basalts have incompatible element and Sr-isotope ratios that are intermediate between the intraplate basalts from the African plate (e.g. Pantelleria) and the calc-alkaline mafic rocks from Alicudi (Aeolian arc). This has led to the conclusion that the source of Ustica magmas is an intraplate-type mantle contaminated by subduction fluids or melts. A similar conclusion has been reached by Trua et al. (2003).

in the Iblei Plio-Quaternary volcanoes requires more complex sources than at Etna and Ustica. Beccaluva et al. (1998) used an integrated thermodynamic, geochemical and isotopic approach to reach the conclusion that tholeiitic to nephelinitic lavas were generated by variable degrees of lithospheric mantle melting (about 20% for tholeiites and about 3% for nephelinites) at various pressures (from 1.0 to 2.5 GPa passing from tholeiites to nephelinites). The mantle rocks were lherzolites containing some amphibole at shallow depth and amphibole plus phlogopite and carbonates at greater depth. These exotic mantle minerals were formed by reaction between depleted lithospheric mantle and percolating fluids or melts. Metasomatism was stronger at the base of the lithosphere, where alkaline melts were generated, with respect to the intermediate and upper lithospheric mantle, which generated tholeiitic magmas.


Summary of geochronological, volcanological and petrological characteristics of the Sicily volcanoes. (Peccerillo, 2005).


• Peccerillo. A. Plio-Quaternary Volcanism in Italy. (2005)