The Tethyan seawater retained in serpentinites of the Hyblean basement (south-eastern Sicily): its role in the igneous activity, tectonic behaviour and oil settings

The study of the xenolith suite found in the Hyblean diatremes (SE Sicily), Upper Tortonian in age, revealed that theunexposed Permo-Triassic basement of the region consists of serpentinized peridotites and minor gabbros, suggestingthe development of oceanic core complex structures (Scribano et al., 2006a,b) in the Paleo-Mesozoic, ultra-slowspreading, Ionian-Tethys Ocean. A recent interdisciplinary study pointed out that serpentinites are the dominant rocksforming the Hyblean-Pelagian basement down to a mean depth of 19 km, representing the Moho interpreted as aserpentinization front (Manuella et al., 2013). The basaltic magma-serpentinite interaction could be responsible ofvarious geochemical and rheological modifications of the former. The serpentinite dehydration originated pressurizedvapour whose violent expansion generated the Hyblean diatremes (Scribano et al., 2007). At the regional scale, repeatedevents of hydration/dehydration generated volume changes of huge masses of serpentinites, which can account thevertical tectonic style of the Hyblean area through geological time. Finally, the finding of hydrocarbons in someHyblean mafic and ultramafic xenoliths suggests that serpentinization process promoted the abiogenic production ofhydrocarbons via Fischer-Tropsch reaction (Ciliberto et al., 2009; Scirè et al., 2011). Thus, serpentinites may representboth source and reservoir rocks of hydrocarbons in south-eastern Sicily.