Preliminary petrographic and volcanological study of “Punta Karuscia-Punta Spadillo” submerged area, Pantelleria Island (Strait of Sicily)

The Pantelleria Island (Mediterranean Sea, Italy) is located in the Sicily Channel Rift Zone (SCRZ) and represents the emergent tip of an underwater volcano complex with 72% lying below sea level, down to a depth of about 1200 m. Its origin is linked to the Pantelleria graben, one of the three main tectonic depressions of the NW-SE trending extensional area SCRZ. The rifting process is active since the Late Miocene and was accompanied by a widespread volcanic activity mainly concentrated on Pantelleria and Linosa islands. The volcanic history of Pantelleria started before 320 ka BP and the volcanic activity was characterized by large explosive events, sometimes followed by caldera collapses, alternated to mild eruptions. The last caldera collapse event (45-50 ka BP) followed the major eruption emplacing the Green Tuff ignimbrite. While the post Green Tuff activity has been reconstructed in detail and subdivided into six silicic cycles (pantellerite to trachytes), interposed with mildly alkaline basalts in the NW sector of the island, the volcanic history of Pantelleria before 50 ka BP is poorly known due to the paucity of rock outcrops. High resolution multibeam bathymetry data (Bosman et al., 2011) show how the volcanic Island rises from a gently sloping seafloor in the NW and in the SE sectors, while is bounded by steep flanks and rimmed by a very narrow or absent shelf on the NW and SW sectors. The definition of the extents and characters of submarine portions of the edifice allow a better comprehension of their structure (Conte et al., 2014). Thus, aimed to provide a contribution in the reconstruction of the evolution of the Pantelleria volcanism, thirteen volcanic rocks were collected in shallow-water, offshore the N-W Pantelleria by SCUBA diving. The rocky outcrops were identified by high resolution multibeam bathymetry data in very shallow water. Preliminary data indicate that the collected samples are variably porphyritic lavas (P.I. = 5-20 % vol) classified as pantellerites and basalt/hawaiites, which features are correlated with those of the emerged area, allowing to outline a preliminary volcanological-map of the submerged sector “Punta Karuscia-Punta Spadillo” of Pantelleria Island in shallow water.