GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 3.2 189 Moreover, the main structure associated to the geothermal system and the connection with the hot springs of Terme Caronte are detected. Finally, in the plain of the town of Lamezia Terme (CZ) reflection and refraction seismic surveys were carried out at high resolution. A seismic profile was acquired and reached a total of 2975 m of investigation depth. The seismic reflection section shows structures related to sub- horizontal stratification on an inclined base and displaced by faults. On the migrated section, in the northern part of the section a series of strong reflectors is evident at a depth of 600-800 m. By the geological characteristics and seismic velocity (> 3000 m/s), these reflectors most probably represent the top of the bedrock. These reflectors deepen toward south, where they are found at a depth of 1200-1400 m. The deepening of the bedrock top and corresponding reflectors at the southern edge of the profile is most probably related to tectonic dislocations, which are evident at surface. Data coming from a new deep bore-hole. Due to the lack of geothermal gradient data in the area of Terme Caronte only an approximate estimate of the depth reached by the thermal waters was possible. A deep borehole integrated with geophysical measurements was therefore planned, in order to improve the assessment of the geothermal potential of the area, and to increase the current knowledge on the relationship between heat flow and deep tectonics, particularly complex in this sector of the Calabrian Arc. The borehole was drilled about 5 km south of the Terme Caronte hot spring, on the Catanzaro Graben. The location of the well was designed combining logistic aspects with the geophysical results obtained by DERT, MT and reflection seismic acquisitions. The well was drilled in the summer 2014 and reached a depth of about 900 m. Several drilling problems, due to the different confined aquifer located in the various geological layers, constrained the company to change the type of coring several times. From geological point of view, the deposits down to 350 m should be associated to late Pleistocene - lower??? units. Below them, down to a depth of about 600 Gelasian (formerly Upper Pliocene) - Early Pleistocene units can be found. From 500-600 m to 800 m Pliocene (Piacenziano-Zanclean) units have been drilled. The final part, from about 800 until the bottom, the cores showconglomeratic terms that are the base of the Pliocene and the roof of theMessinian. The detailed stratrigraphy of the geological formations was obtained and a comparison with the seismic and geoelectrical data was defined using a constrained approach. Therefore, the well data provided more useful information on the geological and hydrogeological complexes in the area and on the potential geothermal in the plain of Lamezia. Conclusion. By integrating geological, geochemical, indirect and direct data, the potential geothermal reservoirs of the study area has been investigated indicating the target depth, expected outflow temperature, and yield of the expected reservoir. The integrated interpretation of surface geology, geochemical analysis, seismic reflection profiles, and Electrical and Electromagnetic data integrated with the borehole stratigraphy, allowed to defining the main features of the overall reservoir/caprock system and its structural-stratigraphic setting. Moreover, the electric and electromagnetic results, calibrated with surface geology, focused on the structural contact between Mesozoic carbonate and alluvial fans that is marked by most of the thermal spring clusters of the area. Thermal water, outcropping at Terme Caronte, resulted to rise along the NW-SE-trending left-lateral strike-slip fault system that separates the Plio-Quaternary Catanzaro Graben from the southern edge of the Sila Massif, i.e. where the entire pile of the Calabrian Terranes and underlying Mesozoic Carbonate Complex crop out, and the oldest N- S fault system. Also, the area of contact with the impermeable Neogene deposits constitute a threshold permeability which tends to hinder the transfer to the Plains of Lamezia Terme. The geochemical studies have demonstrated that the water of the springs of Terme Charon not have elevated shuffles with those surface, demonstrating the presence of a rapid ascent along the two indicated main fault system. Furthermore, considering a thermal gradient of 30-33 °C/km, it can be assumed a depth of the circuit between 2 and 3 km, taking into account the estimated