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- PublicationRestrictedDiscrete monitoring of chemical parameters in ground waters of Mt. Etna volcano: 2000–2006(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Three sites of groundwater captation on Mt. Etna volcano (namely Currone, Ilice and Pavone) were sampled systematically for six years (from2000 to 2006) for the determination of the major ionic composition of water. The monitored siteswere chosen among those most representative of the geochemical characteristics of the groundwater systems of the volcano. The period studied was characterized by several strong eruptions of Mt. Etna, both at its summit craters and along its flanks. The overall composition of the waters sampled at Currone and Ilice falls in the group of bicarbonate-alkaline-earth compositions, whereas those from Pavone show a bicarbonate- alkaline composition. In all sites, however, some samples show input of chlorine-sulfate alkaline waters, likely due to interaction between fresh groundwater and either acidic waters from SO2-polluted rainwater, (more evident at Pavone) or geothermal brines (more evident at Currone). Significant temporal variations affected, in a more or less marked way, all of the parameters measured at the three sites. Basic statistical correlations among the parameters at each site allowed to discover a general coherent temporal behavior of all major ions dissolved in Mt. Etna's ground waters. Factor Analysis allowed showing up to three main groups of parameters with similar temporal behavior, depending on the site. A first group was explained by interaction between volcanic groundwaters and geothermal fluids; a second groupwas related with leaching of the host volcanic rocks by CO2-rich volcanicwater; a third groupwas explained as due to input of plume-SO2-derived sulfate through water recharge. Using normal probability plots for each parameter at the three sites it was possible to reveal different geochemical populations explained as background, anomalous values and, possibly, outliers. Plotting the temporal patterns of all the monitored parameters versus the concurrent eruptive episodes at Mt. Etna, we discovered significant correlations that, although with different intensity and rate depending on the parameter and on the site, highlighted several geochemical processes induced by interaction between cold groundwater and magmatic/hydrothermal fluids, mostly following changes in the ground permeability of the volcanic pile. These processes seemed to be enhanced during periods of shallow magma accumulation inside of the volcano that preceded summit or flank eruptions occurred at Mt. Etna during the monitored period.852 2 - PublicationOpen AccessReconstruction of rocks petrophysical properties as input data for reservoir modeling(2016-11)
; ; ; ; ; ; ; The worldwide increasing energy demand triggered studies focused on defining the underground energy potential even in areas previously discharged or neglected. Nowadays, geological gas storage (CO2 and/or CH4) and geothermal energy are considered strategic for low-carbon energy development. A widespread and safe application of these technologies needs an accurate characterization of the underground, in terms of geology, hydrogeology, geochemistry and geomechanics. However, during pre-feasibility study-stage, the limited number of available direct measurements of reservoirs, and the high costs of reopening closed deep wells must be taken into account. The aim of this work is try to overcome these limits, proposing a new methodology to reconstruct vertical profiles, from surface to reservoir base, of: i) thermal capacity, ii) thermal conductivity, iii) porosity and iv) permeability, through integration of well-log information, petrographic observations on inland outcropping samples and, flow and heat transport modelling. As case study to test our procedure we selected a deep-structure, located in the medium Tyrrhenian Sea (Italy). Obtained results are consistent with measured data, confirming the validity of the proposed model. Notwithstanding intrinsic limitations due to manual calibration of the model with measured data, this methodology represents a useful tool for reservoir and geochemical modellers that need to define petrophysical input data for underground modelling before the well reopening.162 78 - PublicationRestrictedGeochemical Barriers in CO2 Capture and Storage Feasibility Studies(2015-01)
; ; ; ; ; ; ;Cantucci, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Montegrossi, G.; CNR - IGG, Via G. La Pira 4, 50121 Florence, Italy ;Buttinelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vaselli, O.; Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, 50121 Florence, Italy ;Scrocca, D.; CNR - IGAG, P.le A. Moro 5, 00185 Rome, Italy ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; CO2 sequestration in geological formations requires specific conditions to safely store this greenhouse gas underground. Different geological reservoirs can be used for this purpose, although saline aquifers are one of the most promising targets due to both their worldwide availability and storing capacity. Nevertheless, geochemical processes and fluid flow properties are to be assessed pre-, during, and post-injection of CO2. Theoretical calculations carried out by numerical geochemical modeling play an important role to understand the fate of CO2 and to investigate short-to-long-term consequences of CO2 storage into deep saline reservoirs. In this paper, the injection of CO2 in a deep structure located offshore in the Tyrrhenian Sea (central Italy) was simulated. The results of a methodological approach for evaluating the impact that CO2 has in a saline aquifer hosted in Mesozoic limestone formations were discussed. Seismic reflection data were used to develop a reliable 3D geological model, while 3D simulations of reactive transport were performed via the TOUGHREACT code. The simulation model covered an area of >100 km2 and a vertical cross-section of >3 km, including the trapping structure. Two simulations, at different scales, were carried out to depict the local complex geological system and to assess: (i) the geochemical evolution at the reservoir–caprock interface over a short time interval, (ii) the permeability variations close to the CO2 plume front, and (iii) the CO2 path from the injection well throughout the geological structure. One of the most important results achieved in this study was the formation of a geochemical barrier as CO2-rich acidic waters flowed into the limestone reservoir.432 35 - PublicationOpen AccessSpatial distribution of arsenic, uranium and vanadium in the volcanic-sedimentary aquifers of the Vicano–Cimino Volcanic District (Central Italy)(2015)
; ; ; ; ; ; ;Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Poncia, P. P.; Po Valley Operations PTY Ltd, via Ludovisi 16, 00187 Roma, Italy ;Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Tassi, F.; Dipartimento di Scienze della Terra, Università di Firenze, via G. La Pira 4, 50121 Firenze, Italy ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vaselli, O.; CNR - Istituto di Geoscienze e Scienze della Terra, via G. La Pira 4, 50121 Firenze, Italy; ; ; ; ; Arsenic concentrations were analysed for 328 water samples collected in the Vicano–Cimino Volcanic District (VCVD), an areawhere severe contamination of groundwater has become a serious problemfollowing the recent application of the EU Directive on the maximum allowable concentration level for As in drinking waters. In addition, uranium and vanadium concentrations were also analysed in light of the enhanced interest on their environmental toxicity. Waters were collected from springs and wells fed by cold and shallow volcanic–sedimentary aquifers, which locally represent the main drinking water source. Thermal springs (≤63 °C) related to an active hydrothermal reservoir and waters associated with a CO2-rich gas phase of deep provenance were also analysed. The collected data showed that the As concentrations in the shallow aquifers varied in a wide range (0.05–300 μg/L) and were primarily controlled by water–rock interaction processes. High As concentrations (up to 300 μg/L) were measured in springs and wells discharging from the volcanic products, and about 66% exceeded the limit of 10 μg/L for drinkingwaters,whereaswaters circulatingwithin the sedimentary formations displayed much lower values (0.05–13 μg/L; ~4% exceeding the threshold limit). Thermal waters showed the highest As concentrations (up to 610 μg/L) as the result of the enhanced solubility of As-rich volcanic rocks during water–rock interaction processes at high temperatures. Where the local structural setting favoured the rise of fluids from the deep hydrothermal reservoir and their interaction with the shallow volcanic aquifer, relatively higher concentrations were found. Moreover, well overexploitation likely caused the lateral inflow of As-rich waters towards not contaminated areas. Uraniumand vanadiumconcentrations ofwaters circulating in the volcanic rocks ranged from0.01 to 85 μg/L and 0.05 to 62 μg/L, respectively. Less than 2% of analysed samples exceeded theWorld Health Organization's provisional guidelines for U (30 μg/L), while none of them was above the Italian limit value of V in drinking water (120 μg/L). Lower U (0.07–22 μg/L and 0.02–13 μg/L, respectively) and V concentrations (0.05–24 μg/L and 0.18–17 μg/L, respectively) were measured in the water samples from the sedimentary aquifer and thermal waters. Local lithology appeared as the main factor affecting the U and V contents in the shallow aquifers, due to the high concentrations of these two elements in the volcanic formations when compared to the sedimentary units. In addition, high U concentrations were found in correspondence with U mineralization occurring within the VCVD, fromwhich U is released in solution mainly through supergene oxidative alteration. Redox conditions seem to play amajor role in controlling the concentrations of U and V inwaters. Oxidizing conditions characterizing the cold waters favour the formation of soluble U- and V-species, whereas thermal waters under anoxic conditions are dominated by relatively insoluble species. Geostatistical techniques were used to draw contour maps by using variogram models and kriging estimation aimed to define the areas of potential health risk characterized by As, U and V-rich waters, thus providing a useful tool for water management in a naturally contaminated area to local Authorities.417 619 - PublicationOpen AccessLong-Term Soil Gas Surveys in the Northern Part of the Modena Province Pre, During and After the 2012 Seismic Sequence(2014-12)
; ; ; ; ; ;Sciarra, Alessandra; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cantucci, Barbara; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Galli, Gianfranco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cinti, Daniele; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Quattrocchi, Fedora; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; Three geochemical surveys of soil gas (CO2 and CH4 flux measurements, He, H2, CO2, CH4 and C2H6 concentrations) and isotopic analyses (δ13C–CH4, δD–CH4, δ13C–CO2) were carried out as part of a feasibility study for a natural gas storage site in the Modena Province (Northern Italy), during the 2006-2009 period. In May-June 2012, a seismic sequence (main shocks of ML 5.9 and 5.8) was occurred closely to the investigated area. Chemical and isotopic analysis were repeated in May 2012, September 2012, June 2013 and July 2014.In the 2006-2009 period, at the pre-seismic conditions, chemical composition of soil gas showed that the southern part of the studied area is CH4-dominated, whereas the northern part is CO2-dominated. Relatively anomalous fluxes and concentrations were recorded with a spotted areal distribution. Anyway, CO2 and CH4 values are within the typical range of vegetative and of organic exhalation of the cultivated soil. 2012-2013 soil gas results show CO2 values essentially unvaried with respect to pre-earthquake surveys, while the 2014 values highlight an increasing of CO2 flux in the whole study area. On the contrary, CH4 values seem to be on average higher after the seismic sequence, although with a decreasing trend in the last survey (2014). Isotopic analysis were carried out only on samples with anomalous values. The δ13C-CO2 value suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived) probably related to anaerobic oxidation of heavy hydrocarbons. Methane isotopic data (δ13C-CH4) indicate a typical biogenic origin (i.e. microbial hydrocarbon production) of the CH4, as recognized elsewhere in the Po Plain and surroundings. Obtained results highlight a different CO2 and CH4 behaviour before, during and after the seismic events. These variations could be produced by increasing of bacterial (e.g. peat strata) and methanogenic fermentation processes in the first meters of the soil. No hints of deep degassing can be inferred for the study area after the earthquake, as suggested by isotopic analysis. These achieved outcomes constitute the starting point for subsequent geochemical surveys, in order to assess the temporal variations and to better understand the geochemical processes related to the seismic sequence.212 100 - PublicationRestrictedLarge-scale numerical modelling of CO2 injection and containment phases for an Italian near-coast reservoir using PFLOTRAN(2014-06)
; ; ; ;Orsini, P.; BLOSint LTD, Triumph Road , Nottingham, NG7 2TU, UK ;Cantucci, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; A potential CO2 storage site located offshore the west coast of Italy, has been modelled using PFLOTRAN assuming an injection rate of 1.5 Mtons/year for 20 years. The model predicts a CO2 footprint characterised by a diameter of about 3.5 km and a maximum pressure build up of 38 bars. The solubility trapping has been quantified, predicting a dissolution in brine of 69% and 79% of the total amount of CO2 injected after 1000 and 2000 years respectively. The residual trapping has also been found to play an important role, with 9% and 6% of the injected CO2 being locked into the hosting matrix pores after 1000 and 2000 years respectively. Considering a worst-case scenario for leakages, where zero critical capillarity pressure has been assumed, minor CO2 leakages through the caprock have been identified, caused by the combined effects of the long-term structural trapping and the large and lasting overpressure caused by the CO2 injection in an ideally closed system. Finally, some preliminary work undertaken as part of an ongoing effort to couple a geochemical model to the multi-phase flow simulations reveals i) small changes in mineral volume fraction and porosity during and after the injection (~5% after 1000 years), and ii) a not negligible self-sealing effect due to precipitation of calcite in the lower layer of the caprock. Further investigations and longer physical time runs are needed to confirm this assumption, but also to gain more confidence on the geochemical model built so far and to estimate the mineral trapping potential for this site.363 82 - PublicationRestrictedA newly-emerged (August 2013) artificially-triggered fumarole near the Fiumicino airport, Rome, Italy(2014-05-14)
; ; ; ; ; ; ; ;Sella, P.; Geomagellan, Montecompatri, Rome, Italy ;Billi, A.; Consiglio Nazionale delle Ricerche, IGAG, Rome, Italy ;Mazzini, I.; Consiglio Nazionale delle Ricerche, IGAG, Rome, Italy ;De Filippis, L.; Dipartimento di Scienze, Università Roma Tre, Rome, Italy ;Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; Early in the morning of 24 August, 2013, following by hours the drilling of a shallowborehole in the same spot, a new fumarole producing emissions of CO2-rich gas, water, and mud suddenly appeared at a crossroad along the fenced area of the Fiumicino international airport of Rome, Italy. Similar episodes have been scientifically documented or simply reported in recent and past years. To understandwhy gases are easily entrapped in the shallow subsurface of the Fiumicino area, we used five borehole cores drilled by us, analyzed the stratigraphy of these and other nearby cores, acquired a 2D seismic refraction tomogram, and performed chemical and isotopic analyses of water samples collected from aquifers intercepted by two drilled boreholes. Our boreholes were realized with proper anti-gasmeasures as,while drilling, we recorded the presence of pressurized gases at a specific permeable gravel level. Results showthat, in the study area, gases become mainly entrapped in a mid-Pleistocene gravel horizon at about 40–50 m depth. This horizon contains a confined aquifer that stores the endogenous upwelling gases. The gravel is interposed between two silty–clayey units. The lower unit, very hard and overconsolidated, is affected by fractures that allow ascending gases to bypass the otherwise impermeable shale, permeate the gravel, and dissolve into the aquifer. In contrast, the upper unit is impermeable to fluids and seals the gaspressurized aquifer, which therefore constitutes a source of hazard during human activities such as well drilling, quarrying, and various building-related excavations. As the stratigraphy of the Fiumicino area is very common in large portions of the densely populated Roman area and as the adjacent volcanic districts are hydrothermally active, we conclude that phenomena similar to that observed at Fiumicino could again occur both at Fiumicino and elsewhere in the surrounding region. As a prompt confirmation of our conclusion, we signal that, while writing this paper, new artificially-triggered degassing phenomena occurred off Fiumicino in connection with the construction of the new harbor.339 31 - PublicationOpen AccessEarth is speaking: listen her! On-line questionnaire about anomalous geological and biological phenomena(2014-04)
; ; ; ; ;Sciarra, Alessandra; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Quattrocchi, Fedora; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cantucci, Barbara; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Mazzarini, Francesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; Earthquakes can be associated with non-seismic phenomena which may manifest many weeks before and after the main shock. These phenomena are characterized by ground fractures and soil liquefactions at surface often coupled with degassing events, chemical alterations of water and soils, changes in temperature and/or waters level in the epicentral area. Further manifestations include radio disturbances and light emissions. On the other hand, anomalous behavior of animals has been reported to occur before environmental changes. The co-occurrence of several phenomena may be considered as a signal of subsurface changes, and their analysis may be used as possible forecast indicators for seismic events, landslides, damages in infrastructure (e.g., dam) and groundwaters contamination. In order to obtain an accurate statistical analysis of these factors, a pre-crisis large database over a prolonged period of time is a pre-requisite. To this end, we elaborated a questionnaire for the population to pick up signs about anomalous phenomena like as: animal behavior, geological manifestations, effect on vegetation, degassing, changes on aquifers, wells and springs. After the January 25, 2013, mainshock (ML 4.8) in the Garfagnana seismic district, the Bagni di Lucca Municipality was selected as pilot site for testing this questionnaire. The complexity, variety and extension of this territory (165 kmq) sound suitable for this project. Bagni di Lucca is located in the southern border of the Garfagnana seismogenic source, characterized by the carbonate Mesozoic sequences and the Tertiary terrigenous sedimentary deposits of the Tuscan Nappe. The questionnaire was published on Bagni di Lucca web site (https://docs.google.com/file/d/0Bzw3vOYX47XoTGltTVJRbkJuajA/edit) in collaboration with Municipal Commitee, Local Civil Protection and Local Red Cross, and sent by ordinary mail to the citizenry. It is possible to answer to the questionnaire, also anonymously, direct on line (https://docs.google.com/forms/d/1LVNVQFzMoJJfNxp2eSPAc4pcwj4_qIdbAnvbCWGyXy8/viewform?pli=1), calling the Local Civil Protection or Local Red Cross, and by mail. In a second time, an application for Smartphone and Tablets will be developed to allow a faster reply. The questionnaire, constituted by eleven questions and organized in four macro-themes (i.e. animal behavior, geological factors, vegetation anomalies and hydrogeological changes) has been published in June 2013 and will remain on-line for several years. Indeed, the social perception is not fully trustworthy during and soon after an earthquake. So far this is the first attempt to acquire data during quiescent times for comparison with post-seismic ones. This approach may provide clues to identify phenomena properly linked to the event. This questionnaire can be a useful tool to educate population not only about earthquake precursors but also to recognize the "Earth language". Submitted testimonies will be statistically analyzed evidencing the specific responses to the different phenomena in space and time. On the basis of obtained results the questionnaire project could be extended to national level.182 94 - PublicationRestrictedGeochemical and Geomorphological Analyses on Liquefaction Occurred During the 2012 Emilia Seismic Sequence(SPRINGER, 2014)
; ; ; ; ; ;Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cantucci, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Abu Zeid, N.; Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, ;Vaccaro, C.; Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; Lollino, G:On May 20th and 29th, 2012 two earthquakes (ML 5.9 with hypocenter depth at 6.3 km and ML 5.8 with hypocenter depth at 10.2 km, respectively; ISIDe Database) struck the Emilia area. The epicentre was located in the vicinity of Finale Emilia and Medolla (Modena). Co-seismic effects exemplified by liquefactions and surface ruptures occurred in the surrounding area (Provinces of Bologna, Ferrara, Modena, Reggio Emilia, Mantova and Rovigo). The maximum effects where concentrated along the towns located 15–25 km from the epicentre (SW portion of Ferrara Province). Soon after the main events, several geochemical and geophysical surveys were carried out in different sites at Modena and Ferrara Provinces, where surface rupture and liquefaction effects were most evident. Results gained from soil and dissolved gases and geoelectrical-geophysical surveys evidenced that the main liquefied layer is related to a medium coarse-grained sand saturated aquifer located at 8–12 m b.g.l. On the other hand, superficial unsaturated sediments underwent liquefaction represented by densification and lateral spreading. As a consequence, liquefied soil caused ground failures and damages to the built environment. The extent of the liquefaction phenomena, its concentration along the Reno paleo-river ridge and the building damage, has highlighted the need to further characterized the possible rule of lithology and natural gas content on the outset of liquefaction.332 31 - PublicationRestrictedFluid geochemistry and geothermometry in the unexploited geothermal field of the Vicano-Cimino volcanic district (central Italy)(2014)
; ; ; ; ; ; ; ; ;Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tassi, F.; università di Firenze ;Procesi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Bonini, M.; università di Firenze ;Capecchiacci, F.; università di Firenze ;Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vaselli, O.; università di Firenze ;Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; The Vicano–Cimino Volcanic District (VCVD) is related to the post-orogenic magmatic activity of the peri- Tyrrhenian sector of Central Italy. The chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources: 1) cold Ca-HCO3 to Ca(Na, K)-HCO3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations; and 2) thermal Ca-SO4(HCO3) type waters located in a deep CO2-pressurized reservoir, hosted in carbonate–evaporite rocks and separated from the shallow aquifers by thick sequences of low-permeability formations. Carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate–evaporite reservoir (δ13C–CO2 from−3.1 to+2.2‰vs. VPDB), likely affected by a mantle-rooted CO2. ReleaseofCO2-rich gases from the deep aquifer into the overlying shallow aquifers produces high-CO2 springs and bubbling pools. The spatial distribution of thermal waters and CO2-rich cold discharges is strongly controlled by fractures and faults located in correspondencewith buried structural highs. Stable isotopes (δD and δ18O) suggest thatmeteoric water feeds both the shallowand deep reservoirs. The relatively lowR/Ra values (0.27–1.19) indicate that He ismainly deriving from a crustal source, with minor component from the mantle affected by crustal contamination related to the subduction of the Adriatic plate. Consistently, relatively high N2/Ar and N2/3He ratios and positive δ15N–N2 values (from0.91 to 5.7‰vs. air) characterize the VCVD gas discharges, suggesting the occurrence of a significant “excess” nitrogen. Isotopic compositions of CH4 (δ13C–CH4 and δD–CH4 values from−28.9 to−22.1‰vs. VPDB and from −176 to −138‰ vs. VSMOW, respectively), and composition of light alkanes are indicative of prevalent thermogenic CH4, although the occurrence of abiogenic CH4 production cannot be excluded. The δ34S–H2S values (from+9.3 to+11.4‰vs. VCDT) are consistentwith the hypothesis of H2S production fromthermogenic reduction of Triassic anhydrites. Gas geothermometry in the H2O–H2–Ar–H2S system suggests that the VCVD gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower (b200 °C) than that andmeasured in deep (N2000 m) geothermalwells. This confirms that secondary processes, i.e. steam condensation, gas dissolution in shallow aquifers, re-equilibration at lower temperature, and microbial activity, significantly affect the chemistry of the uprising fluids. Thermal water chemistry supports the occurrence in this area of an anomalous heat flowthat, coupledwith the recent demographic growth, makes this site suitable for direct and indirect exploitation of the geothermal resource, in agreement with the preliminary surveys carried out in the 1970's–1990's for geothermal exploration purposes.763 55