GNGTS 2013 - Atti del 32° Convegno Nazionale

Suer S., 2010: Geochemical Monitoring of the seismic activities and noble gas characterization of the geothermal fields along the eastern segment of the Buyuk Menderes graben (Ph.D. Thesis). Todesco M., Rutqvist J., Chiodini G., Pruess K., and Oldenburg C.M.; 2004: Modeling of recent volcanic episodes at Phlegrean Fields (Italy); geochemical variations and ground deformation. Geothermics 33 (4), pp. 531-547. Troise C., De Natale G., Pingue F., Obrizzo F., De Martino P., Tammaro U., and Boschi E.; 2007: Renewed ground uplift at Campi Flegrei caldera (Italy): New insight on magmatic processes and forecast. Geophys. Res. Lett., 34 (3), L03301, doi: 10.1029/2006GL028545. Fracture influence on thermal water circulation in foredeep basin: preliminary data from the southern Marche foothills, Italy A. Fusari, C. Invernizzi School of Science and Technology, University of Camerino, Italy Introduction. Although the Adriatic side of Italy shows a low heat flow, due to a fast recent sedimentary deposition and meteoric water infiltration, that depresses the geothermal gradient (Della Vedova et al., 2001), some interesting areas are present along this side, and one of these is Acquasanta thermal area (Central Italy, Fig. 1). Here, thermal springs rise along the Tronto river valley and their temperatures range between 27° and 44°C (Galdenzi et al., 2010). Because the geothermal energy is one of the most promising resources for the forthcoming future, with low environmental impact and excellent sustainability, also from an economic point of view, it is important to perform geological and geochemical preliminary studies to evaluate the potential and sustainability of area such as Acquasanta for the development of the geothermal resource for low and medium enthalpy plants. In this frame, a quantitative structural analysis (i.e. Dezayes et al., 2010, Agosta et al., 2010) is important for the identification of preferential infiltration or rising paths of fluids and to assess the reservoir and the cap rock characteristics. In addition, chemical and isotopic analysis of water are important to define the origin and types of water (i.e. Minissale et al., 2002; Armannsson and Fridriksson, 2009) and its deep circulation. Finally, hydrogeological studies are useful to reconstruct a correct water balance. The aim of our work concern a possible modelling of water circulation at depth, in order to evaluate the geothermal potential in this part of the foredeep basin and its relations to important structural elements. So our preliminary studies regard water chemical and stable isotopes analyses (Fusari et al., 2013) and qualitative and semi-quantitative fracture analyses finalized to understand the hydrogeological pattern and the hot waters ascent path, and to produce a model of the possible thermal reservoir. Geological background. The Acquasanta Anticline is one of the positive structures cropping out within the outer part of the Umbria–Marche Central Apennine. This periclinal structure emerges within the siliciclastic Laga Basin, it is a 25 km-long east-vergent fold, trending about N170°, and it is bounded to the east by a thrust with a displacement of few km (Koopman, 1988). The Umbria-Marche sedimentary succession records a regular sin- and post-rift succession which includes Triassic evaporites (Burano Anhydrites), late Triassic– Liassic platform carbonates (Calcare Massiccio), Jurassic to Mid-Miocene pelagic well bedded limestones and marls succession. The entire carbonatic sequence from Calcare Massiccio to Scaglia Rossa Formation, up to 1500–2000 m thick, host the most important aquifers in the area, which are separated by two main marly levels (Marne a Fucoidi and Rosso Ammonitico Formations). The following Oligocene Scaglia Cinerea Formation, a marly unit up to 200 m thick, together with the overlying Miocene marly units (Bisciaro, Marne con Cerrogna and Marne a Pteropodi Formations) constitute the most important regional aquiclude (Galdenzi et al., 2010). Upward, the sin-tectonic siliciclastic Laga Formation fills the Early Messinian Laga foredeep basin (Bigi et al., 2011 and references therein). 251 GNGTS 2013 S essione 1.3