GNGTS 2011 SESSIONE 1.3 nuova concezione nel Mezzogiorno d’Italia. In una logica di integrazione di policy e programmi diversi, per le 4 Regioni del Mezzogiorno identificate come le “Regioni Obiettivo Convergenza”, con il contributo del Programma Interregionale (POI) Energie rinnovabili e risparmio energetico, sono programmate evoluzioni e sviluppi più ambiziosi ed immediatamente utilizzabili a fini produt- tivi, che comprenda tutti gli utilizzi geotermici e, in particolare, quelli di bassa e media temperatu- ra con tecnologie disponibili. Qui, sull’Atlante geotermico si innesta il progetto VIGOR, in cui il dettaglio delle informazioni e dei risultati, il loro livello di fruibilità per Amministrazioni ed impre- se e la definizione di progettualità innovative ed immediatamente utilizzabili a fini produttivi rag- giunge livelli pari ai migliori standard internazionali, come contributo al riequilibrio di condizioni strutturali meno avvantaggiate e in funzione dell’esigenza di attivare il tessuto produttivo. Questi progetti si interfacciano con l’ambito internazionale. Il progetto Intelligent Energy GEOELEC, appena lanciato, guarderà al potenziale per l’EGS (Engineered o Enhanced Geothermal Systems) in Italia inserendolo in una stima europea. Il progetto Geothermal-ERANET, che sta com- pletando in questi giorni la fase di negoziazione, permetterà di organizzare chiamate su progetti di sviluppo tecnologico definiti a livello europeo, e non solo nazionale. Questi progetti hanno in comu- ne l’interesse a definire in tempi brevi il sistema di organizzazione dei dati necessari alla valutazio- ne geotermica, e la predisposizione di banche dati geotermiche a livello internazionale. A questi progetti in corso di finanziamento si aggiunge l’attività di coordinamento delle ricer- che geotermiche in Europa portato avanti dal gruppo geotermico di EERA (European Energy Rese- arch Alliance) che si colloca in maniera strategica nel Set Plan dell’Unione Europea. In questo ambito, che raccoglie e coordina le attività dei gruppi di ricerca più attivi del settore in Europa, ver- ranno presto predisposti i principali temi di ricerca da proporre nelle future chiamate dei Program- mi Quadro dell’UE. Alla definizione di queste tematiche lavorano anche i gruppi riuniti nelle Piat- taforme Tecnologiche costituite sia a livello Nazionale (Piattaforma Tecnologica per la Geotermia, di riferimento per il MIUR) che europeo (Geothermal Technological Platform, coordinata dal- l’EGEC, European Geothermal Energy Council). Nella presentazione saranno discusse le principali tematiche di ricerca in ambito geotermico, le opportunità di collaborazione scientifica e di finanziamento già in atto e previste nel prossimo futuro.

RECOGNITION OF A DEEP WATER COMPONENT IN THE MONFALCONE THERMAL SYSTEM (NORTHERN ADRIATIC COASTLINE) U. Aviani 1, F. Italiano2, R. Petrini1, M. Ponton1, F.F. Slejko1, L. Zini 1 1 Dipartimento di Geoscienze, Università di Trieste, Italy 2 INGV - Sezione di Palermo, Italy Low to moderate temperature geothermal waters (<50 °C) outflow nearby the Monfalcone town, inland the north-eastern border of the Adriatic Sea. Information on these thermal water resources has been so far scarce due to the relatively low discharge temperature that makes them unsuitable for electricity production. However, the Monfalcone waters may become of interest to provide a source for commercial and residential uses, and for geothermal exploitation. The Monfalcone springs could be related to an external Dinaric structure locally belonging to the NW-SE Palmanova Line system, which in the northern sector of the Karst is displaced by the NE-SW trending Sistiana Fault, that as been supposed to continue offshore (Carulli , 2011). The Dinaric thrusts interest the carbonates which are quite fractured and override the foredeep flysch units. The fracture system tapping the Monfalcone deep water reservoir is buried by Quaternary and Late-Cenozoic sediments which in this area generally cover the Adriatic Apulian foreland. Multichannels seismic profiles and high-resolution single-channel profiles acquired by OGS and University of Trieste across the Grado-Marano lagoon and the Gulf of Trieste (Busetti et al., 2008,

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2009), in addition to the results of the deep crustal profile M-18 CROP (Finetti and Del Ben, 2005) and the information from exploration wells inland, indicate the occurrence of SW-verging Dinaric compressive structures, segmented by NE-SW-oriented faults with normal and transcurrent components (Nicolich et al., 2004; Busetti et al., 2009; Cimolino et al., 2010). This tectonic environment allows deep waters to reach the surface at some favourable spot. Waters, which outflow from Upper Cretaceous limestones were collected during different surveys in 2006-2007. The emergence temperature varied between 32.6 and 39.8 °C, and the total salinity was around 13,000 mg/L for the hotter samples. It is worth to note that the outflow temperature decreases linearly as decreasing the electrical conductivity (EC), suggesting the progressive mixing of a saline thermal reservoir with relatively immature and colder waters. Using the Piper diagram, which considers the proportions among major cations and anions, the Monfalcone waters belong to the Na-Cl-SO4-type with a chemistry which approaches the modern 2+ + + 2- - seawater composition. In particular, the Mg , Na , K , SO4 and Cl concentrations are inversely correlated with EC, supporting the hypothesis of mixing of a saline thermal end-member with Cl— poor waters. Similar trends were obtained during pumping experiments. A closer inspection of the observed trends suggests that the low-salinity end-member is consistent with karst-type waters: it is hence likely that the thermal Monfalcone waters interact at different extent with the shallower karst aquifer while moving upward from a deep reservoir into the overlying strata. Some scatter is 2+ - observed for Ca and HCO3 , possibly reflecting the effects of mixing of different waters on the CaCO3 saturation state, the role of different amount of dissolved carbon dioxide or the control of pH on the bicarbonate concentration during mixing of waters with different temperature and alkalinity. The molar Na/Cl ratio is generally close to that of present day seawater; the lack of Na extra ions suggests that membrane filtration processes did not play a significant role during the flow paths and chemical evolution of the waters. The Cl/Br weight ratio is also typical of seawater since these anions generally do not participate to diagenetic reactions with minerals; this supports the marine origin. In particular, during the initial evaporation of seawater both Cl and Br behave conservatively; their concentration increases while the Cl/Br ratio remains constant at the normal seawater value. Variations occur as halite and other chloride minerals start to precipitate, since Br preferentially remains in solution, and the evaporating seawater and evaporite minerals develop characteristic Cl/Br ratio. This allows, in principle, the distinction between formation waters that are remnants of evaporated brines and those formed by congruent dissolution of evaporite minerals. In the case of Monfalcone, the Cl/Br ratio suggests that the seawater component did not undergo extensive evaporation processes consistently with the absence of evaporite deposit in this portion of the stratigraphic section. It has also to be noted that the Cl and Br concentrations plot on a seawater dilution trajectory. The oxygen and hydrogen isotopic compositions do not show significant seasonal trends, suggesting the occurrence of hydrological circuits not directly affected by rapid rainwater recharge. Furthermore, the measured O-H isotope-ratios are lighter compared with modern seawater, indicating that the original marine signature, as indicated by geochemical data, was partially lost during processes occurring within the basin. In particular, the isotopically lighter waters show the lower outlet temperature, supporting the hypothesis that the original oxygen and hydrogen isotopic signature of the thermal reservoir was replaced by the cold end member. This is supported by the covariant trend between δD and chloride content. Since diagenetic effects are negligible for δD, the projection of the trend line to zero chloride concentration indicate a freshwater end-member which is consistent with waters from the Classic Karst aquifer. The dissolved He-CO2-N2 gases lie far from the typical air-saturated water composition, indicating that gases are a mixture of air derived components and deep gases of crustal origin. The crustal origin also is marked by the 3He/4He ratio, always well below the atmosphere. The Sr isotopic composition of Monfalcone waters is in the relatively narrow range between 0.70803 and 0.70814. These values differ from modern seawater (0.70925) and from the Upper Cretaceous limestones (0.7076) which constitute the aquifer. Mass-balance calculations indicate

189 GNGTS 2011 SESSIONE 1.3 negligible effects on the Sr-isotope ratio during mixing of the saline reservoir and karst waters, and assuming that Sr did not experience significant local diagenetic modifications, the measured 87Sr/86Sr ratio is compatible with Oligocene seawater (McArthur et al., 2001). The 11B/10B ratio is also consistent with modified seawater. A possible scenario for the deep thermal component of the Monfalcone waters involves the occurrence of marine paleowaters which penetrated through karstic structures within Cretaceous limestones during the Oligocene prolonged emersion of the platform, entrapped and dispersed by the progressive burial, not completely expelled or replaced by meteoric waters. During their ascent from the hydrothermal system along NE-SW trending faults they underwent mixing at variable extent with shallow cold waters. References Busetti M., Volpi V., Nicolich R., Barison E., Baradello L., Brancatelli G., Marchi M., Romeo R., Wardell N., 2009. The Dinaric thrusts in the Gulf of Trieste (Northern Adriatic). Rendiconti online Soc. Geol. It., Vol. 9: 72-75. Busetti M., Volpi V., Barison E., Giustiniani M., Marchi M., Ramella R., Wardell N., Zanolla C., 2008. Meso-Cenozoic seismic stratigraphy and the tectonic setting of the Gulf of Trieste (northern Adriatic). GeoActa Special Pubblication 3: 15-28. Carulli G.B., 2011. Structural model of the Trieste Gulf: a proposal. J. Geodynamics 51: 156-165. 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: S167-S179. Finetti I.R., Del Ben A., 2005. Crustal Tectono-Stratigraphic Setting of the Adriatic Sea from New CROP seismic Data. In: Finetti I.R. (ed.) CROP Project. Deep Seismic Exploration of the Central Mediterranean and Italy. Atlases in Geoscience 1., Elsevier B.V. Amsterdam, The Netherlands, pp. 519-547. McArthur J.M., Howarth R.J. and Bailey T.R., 2001. Strontium isotope stratigraphy: LOWESS Version 3. Best-fit line to the marine Sr-isotope curve for 0 to 509 Ma and accompanying look-up table for deriving numerical age. J. Geol. 109: 155-169. Nicolich R., Della Vedova B., Giustiniani M., Fantoni R., 2004. Carta del sottosuolo della Pianura Friulana (Map of subsurface of the Friuli Plain). Reg. Aut. FVG, Direzione Centrale Ambiente e Lavori Pubblici, Servizio Geologico, 32 pp.

GROUND DEFORMATION AT CALDERAS DRIVEN BY FLUID INJECTION: MODELLING UNREST EPISODES AT CAMPI FLEGREI (ITALY) A. Troiano, M.G. Di Giuseppe, Z. Petrillo, C. Troise, G. De Natale Istituto Nazionale di Geofisica e Vulcanologia, Dept. Osservatorio Vesuviano, Naples, Italy Campi Flegrei collapse caldera (Italy) is a high risk volcanic area located close to Naples and including part of the densely populated city. Such area is characterised by large up and down ground displacements. The last large uplift episode caused 3.5 m of cumulative vertical displacement at the center of the town of Pozzuoli, in the period 1969-1984. Up and down ground movements at this area, often occurring without intercurring eruptions, are similar to what observed at other calderas worldwide, but appear here more evident and amplified. Understanding the mechanism of such movements is crucial for hazard assessment and eruption forecast, mainly at this densely populated area. This paper presents a detailed model for ground displacements due to deep fluid injection in shallower layers. Such a model explains in a natural way the occurrence of uplift and subsidence without eruptions. For the first time, we show which is possible to fit observed ground deformations at this area with such a fluid-dynamical model. The obtained model is consistent with other observations like microgravity changes, changes in CO2 flux, etc. This paper then rigorously demonstrates that significant uplift and subsidence at calderas can be due to effects of deep fluid injections other than magma. At Campi Flegrei, however, a partial magmatic contribution at the origin of the observed episodes cannot be excluded.

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