The Strait of Sicily continental rift systems: Physiography and petrochemistry of the submarine volcanic centres

Abstract

New morphological, geophysical, mineralogical and petrochemical data on the submarine volcanic centres of the Strait of Sicily continental rift systems lead to the following conclusions: Magma types both in the rift valleys (Pantelleria and Linosa) and plateau areas (Adventure Bank) suggest mantle sources and fractionation processes comparable to those of the Ethiopian Afar section of the East African Rift, despite their different tectonic regimes. However, the volume of the erupted magmas (less than 2000–3000 km 3) indicates the similarity with low-volcanicity (dry) rifts. This is probably related to the peculiar tectonic setting of the Pelagian Block (African Foreland) dominated by extensional transcurrent motions connected with a strong Neogene compressive dextral E W megashear along the Sicilian collisional front. In the plateau regions, the most evolved rocks are hawaiites (Graham Bank) which formed by fractionation in the uppermost mantle, probably at the base of the crust. Magma types vary from quartz tholeiites to basanites. In the rift valleys, the range of magma types is more restricted (transitional to alkali basalts) and a considerable volume of highly evolved magmas, particularly in the axial volcanic complex of the Pantelleria Rift, was produced in crustal magma chambers. Isotopic trace-element evidence suggests the involvement of transitional to enriched MORB- and OIB-type mantle sources in the genesis of the quartz tholeiites, alkali basalts and basanites throughout the Strait of Sicily continental rift system, including the Iblean Plateau.