Geothermal system of the caldera of Pantelleria island (Sicily channel)

Abstract

On the basis of the results of exploration surveys conducted over last three years (as described in the paper "Geothermal Exploration in Island (Sicily Channel): first results." R. Chierici et two deep exploratory wells have been drilled in two different the first one the youngest caldera structure, Caldera Cinque in the south-western of the island, the second outside, close to the northern rim the same caldera. Completely different stratigraphic and conditions have been in the two wells. The well crossed a thick sequence of submarine basalts to a depth of 1200 meters and noted a geothermal gradient of in and low meability conditions. The volcanic sequence of this well characterised by an with of clay and carbonates. The hydrothermal alteration is very to those of the undersea floor hydrothermal system. The well passed through pantellerites and trachytes, the typical and pyroclastic sequence of the volcanic complex. to a depth of about 545 m with dykes From m a subvolcanic body was drilled with a constant composition down to meters (bottomhole). The geothermal gradient range from about m down to about in to only 7 m inside the subvolcanic The hydrothermal alteration is mostly developed from aprox 350 m to 700 m. showing the typical distnbution alteration minerals of the geothermal systems (from argillic an allowing the identification of some preferential circulation zones. A fractured productive zone occurs above the intrusion inside the This productive zone is probably related to the Cinque-Denu Caldera and fractures system