GNGTS 2013 - Atti del 32° Convegno Nazionale

References Cimolino A., Della Vedova B., Nicolich R., Barison E., Brancatelli G.; 2010: New evidence of the outer Dinaric deformation front in the Grado area (NE-Italy). Rend. Fis. Acc. Lincei, 21 , 167-179. Della Vedova B.; 2009: Geothermal potential of the carbonatic platform buried beneath the Veneto and Friuli coastal areas: results from the Grado-1 borehole. FIST Congress, Rimini, September 9-11, E1-E8. Goldscheider N., Mádl-Szónyi J., Eróss A., Schill E.; 2010: Review: Thermal water resources in carbonate rock aquifers. Hydrogeol. J., 18 , 1303-1328. Petrini R., Italiano F., Ponton M., Slejko F.F., Aviani U., Zini L.; 2013: Geochemistry and isotope geochemistry of the Monfalcone thermal waters (northern Italy): inference on the deep geothermal reservoir. Hydrogeol. J., 21 , 1285-1287. Geochemical characterization of the San Calogero thermal spring (Lipari): indications of active juvenile contributions F. Picone 1 , G. Bianchini 1 , F. Italiano 2 , M. Martelli 2 , C. Marchina 1 , N. Colombani 1 , R. Tassinari 1 1 Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Palermo, Italy Introduction. The San Calogero thermal spring is located in the Island of Lipari (Aeolian volcanic arc) and was known (and used) since Greek and Roman times, thus representing an important archeological and cultural site. In this contribution that will be presented at the GNGTS Conference, we report new geochemical and isotopic data that could be useful for a better understanding of the observed thermal components. Results are important taking into consideration the existing project of restoration and qualification of the investigated thermal resource. Geological framework and background information. The Aeolian archipelago is located in the south-eastern margin of the Tyrrhenian sea and is interpreted as a volcanic arc located about 250 km above a subducting slab (Beccaluva et al. , 1985; Peccerillo et al. , 2005). The igneous processes are still effective and represented by active volcanoes: Stromboli, with persistent activity; Vulcano, which had numerous explosive eruptions during historic times, the last of which occurred in 1888-1890; and Lipari where the last eruption took place about 1400 y.b.p. in the northeastern part of the island (Tranne et al. , 2000). Low-temperature fumaroles (80-90 C°) and hot springs are currently the only manifesta- tions of volcanic heat in Lipari. The volcanic and structural evolution of Lipari is well known (Crisci et al. , 1991). The oldest Lipari products consist of 223-150 kyr-old basalt-andesitic lavas erupted from submarine vents and from subaerial volcanoes. The successive volcanism (from 127 to 92 kyr) occurred in the central sector of the island, where the activity of the Mt. S. Ange- lo and Costa d’Agosto volcanoes (high-K andesitic lavas and pyroclastics) developed within the Mt. S. Angelo depression. After a gap in volcanic activity of about 50 kyr, volcanism resumed in the southern sector of the island with the emplacement of rhyolitic–shoshonitic pyroclastics and of the N-S-aligned South Lipari and Mt. Guardia domes (42-20 kyr). This activity devel- oped within a pre-existing volcanotectonic depression formed between 92 and 42 kyr. The last phase of activity on Lipari developed in the northeastern sector of the island where the 11.4-1.41 kyr-old N–S-aligned Gabellotto, Forgia Vecchia, and Pilato rhyolitic eruptive centers occur. The structural setting of Lipari is defined by fault segments and associated fractures which can be grouped in two main sets striking NNW–SSE/NW– SE and from N–S to ENE–WSW. The results of previous geological, structural and geochemical prospecting performed in the study area suggest the possible presence of a high-enthalpy geothermal system on the Island (Bruno et al. , 2000). This system, similar to what was observed in analogous geological envi- ronments, is probably made up by a magmatic heat source and by a convective circulation of shallow waters that seep through the volcanic rocks. Consequently, these waters are heated by the source and rise back to the earth surface. All thermal emergencies discovered on the island seem connected with the tectonic structures cutting the western sector of Lipari. Along some 273 GNGTS 2013 S essione 1.3