The Sicily Province

Abstract

The Sicily Province consists of tholeiitic to Na-alkaline magmas that show OIB-type major and trace element features. Except for Pantelleria, compositions are prevailingly mafic. At Etna (0.5 Ma to Present), early-erupted tholeiitic basalts were followed by Na-alkaline hawaiites to trachytes; hawaiitic magmas are presently erupted from central and parasitic vents. Iblei magmatism (7–1.5 Ma) consists of an association of tholeiitic basalts-basaltic andesites and Na-alkaline basalts and nephelinites, some of which contain mantle xenoliths. Ustica (0.75–0.13 Ma) and Linosa (about 1–0.5 Ma) are built up by mafic rocks with minor benmoreite-trachyte. Pantelleria (320 to <10 ka) is characterised by a bimodal distribution of dominant peralkaline lavas and pyroclastics and minor basalts, with a large Daly gap for intermediate compositions. Seamounts in the Sicily Channel (Graham-Ferdinandea, Foerstner, etc.) are basaltic with variable enrichments in alkalies. Incompatible element contents of mafic rocks in the Sicily Province increase from tholeiites to alkali basalts and nephelinites. Sr–Nd isotopic compositions are poorly variable and resemble FOZO-type OIBs. Range of Pb isotopic ratios is larger and defines a trend between HIMU-FOZO and DMM mantle end-members. Compositions of Sicily mafic magmas are related to different degrees of partial melting of lithospheric to upper asthenospheric mantle sources. About 20% to 3% melting at increasing pressure is suggested to generate tholeiitic to nephelinitic magmas. The variable Pb isotopic signatures reveal mantle heterogeneities that result from interaction between lithosphere and enriched components of deep origin. These may be provided by an ascending plume head or, more probably, by asthenospheric fluids.