Geophysical exploration for geothermal low enthalpy resources in Lipari Island, Italy

Integrated geophysical surveys were performed in two sites, Fossa di Fuardo and Terme di San Calogero in Lipari Island, Southern Italy with the intent of the exploration of low-enthalpy geothermal fluids. Both sites show stro ng geochemical and geologic evidences of hydrothermal activity. The geophys ical methods consist of two microgravimetric surveys, two 2D geoelectric pr ofiles, a seismic reflection profile and a five seismic refraction profiles . The seismic methods allowed us to locate the main subsurface seismic disc ontinuities and to evaluate their geometrical relationships. The gravity fi eld was used to constraint the seismic discontinuities, while the electric prospecting let discriminate more conductive areas, which could correspond to an increase in thermal fluid circulation in the investigated sites. The results obtained by the different geophysical methods are in good agree ment and permit the definition of a reliable geostructural model of the sub surface setting of the two investigated areas. A low-enthalpy geothermal re servoir constituted by a permeable pyroclastic and lava sequence underlying two shallow impermeable formations was found at Fossa del Fuardo. The rese rvoir is intersected by some sub-vertical faults/fractures that probably pl ay an important role in convoying the thermal water up to the surface. At t he other site, Terme di S. Calogero, the geophysical surveys showed that an intense circulation of fluids affects the subsurface of the area. This cir culation concentrates along a ENE-trending fault located at a little distan ce from the thermal resort. The hot fluids may upraise along the fault if t he width of the ascent area is smaller than 20 m. (C) 2000 Elsevier Science B.V. All rights reserved.