http://hdl.handle.net/2122/197 2013-05-22T01:00:41Z http://hdl.handle.net/2122/8632 Title: Preliminary investigation on soil CO2 and soil CH4 effluxes from a geothermal area near Palagonia (Sicily, Italy) Authors: Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Bonfanti, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Carapezza, M. L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pagliuca, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ricci, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Spampinato, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: The central part of eastern Sicily is characterized by several areas of strong crustal degassing. These gases are mostly carbon dioxide and methane and are particularly concentrated in some focused emissions (gas vents, mud volcanoes) or as diffuse degassing along major faults. In this study, the extent and orientation of soil CO2 and soil CH4 effluxes were investigated on a wide area (about 40 km2) located about 50 km southwest of Mt. Etna (Fig. 1). From a structural point of view, this area lays on a typical foredeep - foreland system that marks the boundary between the southern part of the Eurasian plate and the northern part of the African plate in the central Mediterranean. The situation was further complicated by the tectonic subsidence of the foredeep to the north of the northern Hyblean margin (YELLIN-DROR et alii, 1997; CARBONE et al., 1982) and the formation of a series of ENE-WSW oriented grabens and horsts, the Lentini Graben being the most important of these structures. This area was characterized by both submarine and subaerial volcanism until 1.7-2 Ma (BARBERI et alii, 1974; GRASSO et alii, 1983; GURENKO AND SCHMINCKE, 2002; SCHMINCKE et alii, 1997; TRUA et alii, 1997), and it was affected by strong seismicity in historical times. The surface geology consists of recent alluvial deposits and Plio-Pleistocene clays and sands interbedded with coeval basaltic lavas and pyroclastics of alkaline affinity (CARBONE et alii, 1987). Strong gas emissions in this area have been known since pre-Greek times, as reported by FERRARA (1805). PONTE (1919, 1934) showed that the gas that erupted through Naftìa Lake (located just southwest of the village of Palagonia, see Fig. 1) was pure carbon dioxide and calculated total emissions at about 80,000 t d-1. Today, the main gas emission is exploited for commercial use (Mofeta dei Palici plant, CO2 output estimated as about 250 t d-1, R. Romano pers. comm., 1998). The area is also characterized by several water well with warm (20-50 °C) water. Recent geochemical studies on this area (DE GREGORIO et alii, 2002; CARACAUSI et alii, 2003a, 2003b; GIAMMANCO et alii, 2007) showed that anomalous CO2 degassing has a hydrothermal or magmatic origin and it is linked to the dynamics of Mt. Etna’s plumbing system. 2012-08-31T22:00:00Z http://hdl.handle.net/2122/8522 Title: A simple and sensitive gas chromatography–electron capture detection method for analyzing perfluorocarbon tracers in soil gas samples for storage of carbon dioxide Authors: Nazzari, M.; 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 Abstract: Co-injection of a conservative tracer during the geological sequestration of CO2 can imprint a marker to the injected gas that can be easily recognized during soil gas surveys in case of CO2 leakage from the reservoir toward the surface. In this work, an ultra-trace detection method, based on gas chromatography with electron capture detection for analyzing perfluorocarbon tracers (PFTs) in soil gas samples was optimized. Three totally fluorinated cycloalcane compounds consisting of five and six atom carbon rings were selected for this purpose. We evaluated the feasibility of collecting PFTs on adsorbent tube packed with a commercial graphitized carbon black (Carbotrap™ 100) sampling 2 L of soil gas. The sorbent tubes were then analyzed by using a two-stage thermal desorption process. The developed method allows to quickly determine these compounds at very low fL/L level, method identification limits ranged from 1.3 to 5.8 fL/L. Moreover, it shows good precision, evaluated by within-day and between-day studies. A preliminary survey of the PFT soil gas background concentrations, conducted by analyzing some soil gas samples collected in two different areas in Central Italy and in the Po Plain, ascertained the PFT background concentration lower than MIL. 2013-04-30T22:00:00Z http://hdl.handle.net/2122/8260 Title: Thermal fluids along the East Anatolian Fault Zone (EAFZ): geochemical features and relationships with the tectonic setting Authors: Italiano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Sasmaz, A.; Department of Geology, Elazig Turkey; Yuce, G.; Eskisehir Osmangazi University – Department of Geology, Eskisehir Turkey; Ocan, O.; Fırat University – Department of Geology, Elazig Turkey Abstract: A geochemical investigation has been carried out on the gas phase associated to thermal fluids discharged along three different segments of the East Anatolian Fault Zone (EAFZ, Turkey) running from Malatya to the Triple Junction area (Karliova) where the East and North Anatolian Faults cross each other. CO2 is always the major gaseous component in both bubbling and dissolved gases with variable amounts of nitrogen helium and CH4. The isotopic ratios of helium range from 0.44 to 4.41Rac (values corrected for the atmospheric contamination) and cover a range spanning from crustal to magmatic-type values. The isotopic composition of carbon (CO2) shows values in the range from -5.6 to -0.2 ‰ vs PDB for the bubbling gases in contrast with the positive values (from 0.3 to 3.4‰ vs PDB) detected for the Total Dissolved Inorganic Carbon (TDIC). Coupling the information from the isotopic and chemical composition, it results that mantle-derived fluids are driven to the surface by lithospheric structures. Despite the absence of outcropping volcanic products, the tectonic setting of the different segments plays a major role in releasing mantle-type fluids . The mantle derived fluids interact at shallower levels with circulating waters and originate geothermal systems which equilibration temperatures are estimated to be up to 360°C. The collected thermal fluids show different geochemical features consistent with processes occurring at two different levels: a deep level where mantle-originated fluids are taken either from the upper mantle and from intruded magma batches, and a shallower level, in the upper crust, where Gas Water Interactions (GWI), secondary CO2 production, fractionation processes induced chemical and isotopic modifications of the pristine gas composition. 2012-12-31T23:00:00Z http://hdl.handle.net/2122/7633 Title: Regional groundwater flow and interactions with deep fluids in western Apennine: the case of Narni-Amelia chain (Central Italy) Authors: Frondini, F.; Dipartimento di Scienze della Terra, Universita` di Perugia, Piazza dell’Universita`, Perugia, Italy; Cardellini, C.; Dipartimento di Scienze della Terra, Universita` di Perugia, Piazza dell’Universita`, Perugia, Italy; Caliro, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Morgantini, N.; ARPA Umbria, Via Pievaiola, San Sisto, Perugia, Italy Abstract: The elemental fluxes and heat flow associated with large aquifer systems can be significant both at local and at regional scales. In fact, large amounts of heat transported by regional groundwater flow can affect the subsurface thermal regime, and the amount of matter discharged towards the surface by large spring systems can be significant relative to the elemental fluxes of surface waters. The Narni-Amelia regional aquifer system (Central Italy) discharges more than 13 m3 sec)1 of groundwater characterised by a slight thermal anomaly, high salinity and high pCO2. During circulation in the regional aquifer, groundwater reacts with the host rocks (dolostones, limestones and evaporites) and mixes with deep CO2-rich fluids of mantle origin. These processes transfer large amounts of dissolved substances, in particular carbon dioxide, and a considerable amount of heat towards the surface. Because practically all the water circulating in the Narni-Amelia system is discharged by few large springs (Stifone-Montoro), the mass and energy balance of these springs can give a good estimation of the mass and heat transported from the entire system towards the surface. By means of a detailed mass and balance of the aquifer and considering the soil CO2 fluxes measured from the main gas emission of the region, we computed a total CO2 discharge of about 7.8 · 109 mol a)1 for the whole Narni-Amelia system. Finally, considering the enthalpy difference between infiltrating water and water discharged by the springs, we computed an advective heat transfer related to groundwater flow of 410 ± 50 MW. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7631 Title: Time-dependent CO2 variations in Lake Albano associated with seismic activity Authors: Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Tassi, F.; Department of Earth Sciences, University of Florence,Via G. La Pira 4, 50121 Florence, Italy; Caliro, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Chiarabba, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Vaselli, O.; Department of Earth Sciences, University of Florence,Via G. La Pira 4, 50121 Florence, Italy; Rouwet, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: Lake Albano (Alban Hills volcanic complex, Central Italy) is located in a densely populated area near Rome. The deep lake waters have significant dissolved CO2 concentrations, probably related to sub-lacustrine fluid discharges fed by a pressurized CO2-rich reservoir. The analytical results of geochemical surveys carried out in 1989 2010 highlight the episodes of CO2 removal from the lake. The total mass of dissolved CO2 decreased from ∼5.8× 107 kg in 1989 to ∼0.5×107 kg in 2010, following an exponential decreasing trend. Calculated values of both dissolved inorganic carbon and CO2 concentrations along the vertical profile of the lake indicate that this decrease is caused by CO2 release from the epilimnion, at depth <9 m, combined with (1) water circulation at depth <95 m and (2) CO2 diffusion from the deeper lake layers. According to this model, Lake Albano was affected by a large CO2 input that coincided with the last important seismic swarm at Alban Hills in 1989, suggesting an intimate relationship between the addition of deep-originated CO2 to the lake and seismic activity. In the case of a CO2 degassing event of an order of magnitude larger than the one that occurred in 1989, the deepest part of Lake Albano would become CO2-saturated, resulting in conditions compatible with the occurrence of a gas outburst. These results reinforce the idea that a sudden CO2 input into the lake may cause the release of a dense gas cloud, presently representing the major volcanic threat for this densely populated area 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7355 Title: Study of the geothermal potential of Tetitlan area (Nayarit, Mexico) Authors: Voltattorni, Nunzia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: The soil-gas method has been widely used to infer the nature of subsurface geology/geochemistry since gases released from active geothermal systems, can freely rise through overlying cover to be detected in the near-surface. The high mobility of some gases makes them the best pathfinders for concealed natural resources. Indeed, the gases produced and/or accumulated in geothermal reservoirs can escape towards the surface by diffusion, through transportation by rising hot fluids and by migration along fractures and faults. The Tetitlan area (Nayarit, Mexico) has been investigated by CFE (Comisiòn Federal de Electricidad) since nineties by means of exploratory wells for geothermal purposes and gravimetric prospectings. On the basis of obtained results, a potential deep geothermic reservoir has been inferred in spite of the scarcity of evident surface manifestations (e.g., hot springs, vents). A total of 154 soil-gas samples and 346 CO2 and CH4 flux measurements were collected in an area of 72 square kilometres. The performed soil-gas and flux geochemical surveys highlighted a general rising patterns linked to local fault system. Experimental variograms confirmed the presence of anisotropies highlighting different spatial domains. The contour maps elaborated on the basis of the calculated experimental variograms, demonstrated that gas emission at the surface is not spatially heterogeneous within studied area with the important implication that the highest fluxes, as well as concentrations, could be used in undeveloped geothermal systems to identify main upflow regions and areas of increased and deep permeability. Further, the total natural gas emission has been calculated in order to estimate the exploitation potential of the inferred system. The overall calculated levels of CO2 and CH4 emissions (2.35 104 t/day and 6.6 103 t/ day, respectively) from the Tetitlan system is found to remain within the range of normalized emissions measured for geothermal, volcanic, non-volcanic and hydrothermal systems worldwide. 2011-09-22T22:00:00Z http://hdl.handle.net/2122/7348 Title: Determining the origin of carbon dioxide and methane in the gaseous emissions of the San Vittorino plain (central Italy) Authors: Giustini, F.; CNR; Blessing, M.; BRGM; Brilli, M.; CNR; Lombardi, S.; University La Sapienza; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We are presenting here both chemistry and isotope ratios of helium (He), carbon (13C) and hydrogen (D) of free gases collected in the San Vittorino plain, an intramontane depression of tectonic origin, in order to provide new constraints to better understand mantle degassing in central Italy. Carbon isotopic composition of the carbon dioxide (δ13C-CO2 -2.0‰ to -3.8‰) and He isotope ratios (R/RA 0.12 to 0.27) are used to calculate the fraction of CO2 originating from mantle degassing versus sedimentary sources. Results show that CO2 predominantly (average of 80%) derives from thermo-metamorphic reaction of limestone. The remaining 20% are attributed to a mantle source. The presence of tectonic dislocations allows upward gas migration from a deep source to the Earth’s surface, not only in the peri-Tyrrhenian sector, but also in the more eastern part of central Italy. Isotope ratios of methane (13C-CH4 -6.1‰ to -22.7‰; D-CH4 -9‰ to -129‰) shows that the gas vent releases gas of thermogenic origin, involving CO2 and/or organic matter. Methane seems not to be related to mantle or magma degassing, but seems to be affected by microbial oxidation process. 2010-12-31T23:00:00Z http://hdl.handle.net/2122/7347 Title: The contribution of fluid geochemistry to define the structural pattern of the 2009 L’Aquila seismic source Authors: Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pizzi, A.; DIGAT; Gori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Boncio, P.; University G. d'Annunzio; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: Field investigations performed in the epicentral area within the days following the April 6, 2009 L’Aquila earthquake (Mw 6.3) allowed several researchers to detect evidence of coseismic ground rupturing. This has been found along the Paganica Fault and next to minor synthetic and antithetic structures. Although a lot of geo-structural and geophysical investigations have been recently used to characterize these structures, the role of the different fault segments – i.e. as primary or secondary faults – and their geometrical characteristics are still a matter of debate. In light of this, we have here integrated data derived from fluid geochemistry analyses carried out soon after the main-shock with field structural investigations. In particular, we compared structural data with CO2 and CH4 flux measurements, as well as with radon and other geogas soil concentration measurements (see details in Voltattorni et al., this issue). Our aim was to better define the structural features and complexities of the activated Paganica Fault. Here, we show that, in the near rupture zone, “geochemical signatures” could be a powerful method to detect earthquake activated fault segments, even if they show subtle or absent geological-geomorphological evidence and are still partially “blind”. In detail, a clear degassing zone was identified just along the San Gregorio coseismic fracture zone – i.e., the surface deformation related to the "blind" San Gregorio normal fault. Indeed, CO2 and CH4 flux maximum anomalies were aligned along the Northern sector of the San Gregorio fault, in the Bazzano industrial area. This area also corresponds to the depocenter of the maximum coseismic deformation highlighted by DInSAR analysis (ATZORI ET AL., 2009). Here, maximum radon concentration values in soil gases were also found. As a whole, these results corroborates the hypothesis of BONCIO ET AL. (2010) who suggested that the San Gregorio fault probably represents a synthetic splay of the Paganica Fault, being thus connected with the main seismogenic fault at depth.Moreover, another maximum in CO2 flux anomaly has been measured along the southernmost tip of the earthquake rupture zone, close to the San Gregorio village. Minor or absent soil gas and flux anomalies were instead located along antithetic structures as the Bazzano and Fossa faults, while some anomalies in CO2 flux or radon concentration in groundwater have been found within transfer zones, such as the step-over zone between the central segment of the Paganica fault and the San Gregorio fault and in the zone which separates the Paganica fault from the i) Middle Aterno Valley- Subequana Valley and ii) Barisciano-S. Pio delle Camere-Navelli fault systems. Our results corroborate the power of fluid geochemistry in investigating the structural features of active tectonic structures, being particularly helpful in discerning blind faults. More specifically, our data suggest that the youngest fault splays, as in the case of the San Gregorio fault, may represent preferential sites for degassing. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7334 Title: Soil gas degassing during the 2009 L’Aquila earthquake: study of the seismotectonic and fluid geochemistry relation Authors: Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Gasparini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: A Mw 6.3 earthquake occurred on April 6, 2009 in the Abruzzo region (Central Italy),close to the city of L’Aquila. The aftershock area extended for a length of more than 35 km and included major aftershocks and thousands of minor events. The earthquake ruptured North-West (NW)–South-East (SE) oriented normal fault dipping toward the South-West (SW), with the city of L’Aquila lying a few kilometers away on the hanging wall. A soil gas survey (CO2 and CH4 flux measurements, soil gas measurements and collection) has been carried out in an area of 24 km2 (few kilometers far from L’Aquila city) both to investigate the gas-bearing properties of local seismogenic faults (Paganica, Bazzano, and Monticchio-Fossa faults) and to locate fracture systems when masked by unconsolidated lithologies. Anomalous values of Rn and CO2 were detected both east of Bazzano fault and in the central part of the investigated area where faults have no surface expression. Highest He and CH4 values prevail in the southern sector in correspondence with Onna village located between Fossa and San Gregorio faults. Results of this research provide some clues on the spatial influence of active tectonic on gas migration toward the surface. 2012-01-16T23:00:00Z http://hdl.handle.net/2122/7331 Title: Soil gas geochemistry for the study of far- and near-field gas migration mechanisms. Authors: Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Beaubien, S. L.; Universy La Sapienza; Lombardi, S.; Univeristy La Sapienza Abstract: Detailed soil-gas surveys have been conducted at two mine districts to better comprehend gas migration mechanisms from deposits buried at different depths. The Tolfa (Lazio, Central Italy) and Neves-Corvo (Baixo Alentejo, Portugal) mine districts have different characteristics: the former is superficial (30-100 m) while the latter is located at a depth of 400-500 m and covered by low-permeability metamorphic rocks. The soil-gas results from these two different investigated areas provide interesting results related to the study of far- and near-field gas migration mechanisms. In particular, the anomalous concentrations of sulphur compounds (COS, CS2 e SO2), CO2, and Rn confirmed the presence of the two ore deposits. Furthermore, radon was found to be sensitive to soil permeability variations and to be associated with migration pathways (faults and/or fractures). Overall the results indicate the potential for using the studied gas species as indicators of deep seated ore deposits (i.e. in the Neves-Corvo mine district), even at locations where there is thick overburden and no surface evidence. 2010-12-31T23:00:00Z