http://hdl.handle.net/2122/197 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/6035 Titolo: Insights into fluid circulation across the Pernicana Fault (Mt. Etna, Italy) and implications for flank instability<br/><br/>Autori: Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Tripaldi, S.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Piscitelli, S.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Balasco, M.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Magri, C.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Naudet, V.; Université Bordeaux 1, Geosciences Hydrosciences Material and Constructions, GHYMAC-EA 4134, Talence, F-33405, France; Rizzo, E.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy<br/><br/>Abstract: We conducted geophysical–geochemical measurements on a ∼2 kmN–S profile cutting across the PernicanaFault, one of the most active tectonic features on the NE flank of Mt. Etna. The profile passes from theunstable E flank of the volcano (to the south) to the stable N flank and significant fluctuations in electricalresistivity, self-potential, and soil gas emissions (CO2, Rn and Th) are found. The detailed multidisciplinaryanalysis reveals a complex interplay between the structural setting, uprising hydrothermal fluids, meteoricfluids percolating downwards, ground permeability, and surface topography. In particular, the recoveredfluid circulation model highlights that the southern sector is heavily fractured and faulted, allowing theformation of convective hydrothermal cells. Although the existence of a hydrothermal system in a volcanicarea does not surprise, these results have great implications in terms of flank dynamics at Mt. Etna. Indeed,the hydrothermal activity, interacting with the Pernicana Fault activity, could enhance the flank instability.Our approach should be further extended along the full extent of the boundary between the stable andunstable sectors of Etna for a better evaluation of the geohazard in this active tectonic area. Thu, 01 Apr 2010 00:00:00 GMT http://hdl.handle.net/2122/5835 Titolo: Soil-gas geochemistry as permeability tracer of thermally altered clays at Orciatico (Tuscany, Central Italy)<br/><br/>Autori: Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Lombardi, S.; University of Rome "La Sapienza"; Rizzo, S.; University of Rome "La Sapienza"<br/><br/>Abstract: The physical properties of clay allow to consider argillaceous formations as geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation.The thermally altered clays of the Orciatico area (Tuscany, Central Italy) represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil-gas surveys in order to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different thermal alteration degrees. In particular, soil-gas radon and carbon dioxide distributions highlighted that the clay sequences, in spite of their thickness and plasticity, if fractured and metamorphosed, form a lesser impermeable barrier for naturally migrating gas. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5824 Titolo: Gas geochemistry of natural analogues for the studies of geological CO2 sequestration<br/><br/>Autori: Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Caramanna, G.; University of Rome "La Sapienza"; Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Geological sequestration of anthropogenic CO2 appears to be a promising method for reducing the amount of greenhouse gases released to the atmosphere. Geochemical modelling of the storage capacity for CO2 in saline aquifers, sandstones and/or carbonates should be based on natural analogues both in situ and in the laboratory. The main focus of this paper has been to study natural gas emissions representing extremely attractive surrogates for the study and prediction of the possible consequences of leakage from geological sequestration sites of anthropogenic CO2 (i.e., the return to surface, potentially causing localised environmental problems). These include a comparison among 3 different Italian case histories: i) the Solfatara crater (Phlegraean Fields caldera, southern Italy) is an ancient Roman spa. The area is characterized by intense and diffuse hydrothermal activity, testified by hot acidic mud pools, thermal springs and a large fumarolic field.. Soil gas flux measurements show that the entire area discharges between 1200 and 1500 tons of CO2 a day; ii) the Panarea island (Aeolian islands, southern Italy) where a huge submarine volcanic-hydrothermal gas burst occurred in November, 2002. The submarine gas emissions chemically modified seawater causing a strong modification of the marine ecosystem. All of the collected gases are CO2-dominant (maximum value: 98.43 vol. %); iii) the Tor Caldara area (Central Italy), located in a peripheral sector of the quiescent Alban Hills volcano, along the faults of the Ardea Basin transfer structure. The area is characterized by huge CO2 degassing both from water and soil. Although the above mentioned areas do not represent a storage scenario, these sites do provide many opportunities to study near-surface processes and to test monitoring methodologies. Sun, 03 May 2009 00:00:00 GMT http://hdl.handle.net/2122/5823 Titolo: Rn, He and CO2 soil-gas geochemistry for the study of active and inactive faults<br/><br/>Autori: Lombardi, S.; University of Rome "La Sapienza"; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Two Italian areas, characterized by different seismological histories, were investigated in order to enhance the basic knowledge of gas migration mechanisms along fracture and fault surfaces during earthquakes. Sharp variations occur in the movement and concentration of some gaseous species due to the evolution of the local stress regime. The first area (named Colpasquale) is located in the central Italian region of Marche and provided a good location to study gas migration in a seismically active region. The area was devastated by a sequence of shallow earthquakes over a three month-long period (September-December, 1997). The occurrence of this catastrophic event as well as the long duration of the "seismic sequence", presented a unique opportunity to apply a study of gas migration to a zone undergoing active displacement. Soil-gas surveys were performed one day, one week, one year and two years after the main shock (Ms 5.6) in the Colpasquale area. In particular, results highlighted a change of the radon distribution during the three monitoring years indicating a variation of gas migration that may be linked to the evolution of the stress regime.The second study area is located in the Campidano Graben (southern part of Sardinia Island). This area is characterized by seismic quiescence, displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity. The consistently low values observed for all analysed gases suggest that the studied area is characterised by self-sealing probably non-active faults that prevent significant gas channelling.The comparison of data from both studied areas indicate that soil-gas geochemistry is useful to locate tectonic discontinuities even when they intersect non-cohesive clastic rocks (unconsolidated sediments) near the surface and thus are not visible (e.g. “blind faults”). Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5818 Titolo: The application of soil gas technique to geothermal exploration:study of “hidden” potential geothermal systems<br/><br/>Autori: Voltattorni, N.; 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<br/><br/>Abstract: Geochemical studies were conducted using soil-gas and flux surveyings for locating both permeable zones in buried reservoirs and the presence of possible gaseous haloes linked to active geothermal systems. In this work we focused our interest on the distribution of soil-gas concentrations (Rn, Th, He, H2, O2, N2, CO2, CH4 and H2S) in the soil air of the Tetitlan area (Nayarit, Mexico) considered a potential thermal field and characterized by scarcity of surface manifestations. A total of 154 soil-gas samples and 346 CO2 and CH4 flux measurements were collected in an area of about 80 square kilometres. The performed soil-gas and flux geochemical surveys highlighted a general rising patterns linked to local fault system, with the important implication that the highest CO2 and CH4 fluxes, as well as Rn concentrations, could be used in undeveloped geothermal systems to identify main upflow regions and areas of increased and deep permeability. Sun, 25 Apr 2010 00:00:00 GMT http://hdl.handle.net/2122/5816 Titolo: The application of soil gas technique to geothermal exploration:<br/><br/>Autori: Voltattorni, N.; 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<br/><br/>Abstract: Geochemical studies were conducted throughout soil gas and flux surveying for locating both permeable zones in buried reservoirs and the presence of possible gaseous haloes linked to active geothermal systems. In this work we focused our interest on the distribution of soil gas concentrations (Rn, Th, He, H2, O2, N2, CO2, CH4 and H2S) in the soil air of the Tetitlan area considered a potential thermal field and characterized by scarcity of surface manifestations. Radon is used as a tracer gas to provide a qualitative idea of gas transfer (velocity and flux), carbon dioxide and methane are believed to act as carriers for other gases (i.e., Rn and He), helium and hydrogen are used as shallow signals of crustal leaks along faults (Ciotoli et al., 2005). Methane is also considered both a characteristic biogenic indicator of organic matter deposits and a tracer of major crustal discontinuity. A total of 154 soil gas samples were collected in an area of about 80 square kilometres. The same area was investigated throughout a total of 346 of CO2 and CH4 flux measurements. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5814 Titolo: Soil-Gas Geochemistry as Permeability Tracer of Thermally Altered Clays at Orciatico (Tuscany, Central Italy)<br/><br/>Autori: Lombardi, S.; University of Rome "La Sapienza"; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: The physical properties of clay allow to consider argillaceous formations as geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation.The thermally altered clays of the Orciatico area (Tuscany, Central Italy) represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil-gas surveys in order to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different thermal alteration degrees. In particular, soil-gas radon and carbon dioxide distributions highlighted that the clay sequences, in spite of their thickness and plasticity, if fractured and metamorphosed, form a lesser impermeable barrier for naturally migrating gas. Tue, 29 Sep 2009 00:00:00 GMT http://hdl.handle.net/2122/5690 Titolo: Submarine Hydrothermal Activity on the Aeolian Arc: New evidence from Helium Isotopes<br/><br/>Autori: Lupton, John; NOAA/PMEL Newport, USA; De Ronde, Cornel; GNS Science, New Zealand; Beker, Edward; NOAA/PMEL Seattle, USA; Italiano, Francesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Sprovieri, Mario; CNR-IAMC, Napoli; Bruno, Pier Paolo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Faure, Kevin; GNS Science, New Zealand; Walker, Sharon; NOAA/PMEL, Seattle, USA<br/><br/>Abstract: In November 2007 we conducted a water-column and seafloor mapping study of the submarine volcanoes of the Aeolian Arc in the southern Tyrrhenian Sea aboard the R/V Urania. A total of 26 CTD casts were completed, 13 vertical casts and 13 tows. In addition to in situ measurements of temperature, conductivity, pressure and suspended particles, we also collected discrete samples for helium isotopes, methane, and trace metals. The helium isotope ratio, which is known to be an unambiguous indicator of hydrothermal input, showed a clear excess above background at 5 out of the 10 submarine volcanoes surveyed. We found the strongest helium anomaly over Marsili seamount, where the 3He/4He ratio reached maximum values of 3He = 23% at 610 m depth compared with background values of ~ 7%. We also found smaller but distinct 3He anomalies over Enerato, Eolo, Palinuro, and Secca del Capo. We interpret these results as indicating the presence of hydrothermal activity on these 5 seamounts. Hydrothermal venting has been documented at subsea vents offshore of the islands of Panarea, Stromboli, and Vulcano (Dando et al., 1999; Di Roberto et al., 2008), and hydrothermal deposits have been sampled on many of the submarine volcanoes of the Aeolian Arc (Dekov and Savelli, 2004). However, as far as we know this is the first evidence of present day hydrothermal activity on Marsili, Enerato, and Eolo. Samples collected over Filicudi, Glabro, Lamentini, Sisifo, and Alcioni had 3He very close to the regional background values, suggesting either absence of or very weak hydrothermal activity on these seamounts. Helium isotope measurements from the background hydrocasts positioned between the volcanoes revealed the presence of an excess in 3He throughout the SE Tyrrhenian Sea. These background profiles reach a consistent maximum of about 3He = 11% at 2300 m depth. Historical helium profiles collected in the central and northern Tyrrhenian Sea in 1987 and 1997 do not show this deep 3He maximum (W. Roether and B. Klein, private comm.). Furthermore, the maximum is too deep to be attributed to the volcanoes of the Aeolian Arc, which are active at <1000 m depth. We are currently conducting additional measurements to determine whether this deep 3He maximum is from a local hydrothermal source or is somehow related to the deep water mass transient which occurred in the eastern Mediterranean in the 1990’s. Mon, 15 Dec 2008 00:00:00 GMT http://hdl.handle.net/2122/5604 Titolo: Insights into explosive mechanisms controlling lava fountains from remote sensing gas<br/><br/>Autori: La Spina, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Burton, M. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Allard, P.; Laboratorie Pierre Süe, CNRS-CEA, CE-Saclay, 91191 Gif sur Yvette, France; Murè, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia<br/><br/>Abstract: The southeast crater (SEC) of Etna produced fifteen lava fountains in the period June-July 2001,immediately before the 2001 flank eruption. Here we present results from remote sensingmeasurements of the gas phase powering nine of these events, measured using FTIR (Fouriertransform infrared) spectrometry. The spectrometer (Bruker OPAG-22) was located approximately1 km distance from SEC, and spectra were collected every ~6 s using lava jets as the source ofradiation. Spectra were analysed using a non-linear least squares fitting procedure and a forwardmodel with spectral information from the HITRAN database. One challenge posed by measuring alava fountain is the rapidly changing temperature of the absorbing gases. This was addressed byfitting the volcanic gas temperature together with gas amount during analysis of a SO2 absorptionband at 2500 cm-1. With this approach we were able to robustly measure SO2, HCl and HF and,with greater difficulty due to atmospheric interference, CO2 and H2O. Previous work (Allard et al.,Nature, 2005) on one similar lava fountain at SEC in June 2000 has shown that the probablemechanism driving the activity is accumulation of a bubble foam layer ~2 km beneath SEC. Herewe analyse and interpret the temporal variations of SO2/HCl ratio during each event, and comparewith contemporaneous measurements of the volcanic tremor and video recordings of the activity.We find that the measured gas composition displays a close relationship with the evolution oferuptive activity in three successive phases: i) lava effusion and steadily increasing Strombolianactivity, ii) eruption paroxysm culminating in the lava fountain itself, and iii) post-paroxysmalphase with weakening Strombolian activity. Distinct gas compositions can be attributed to eachphase of this sequence, constraining the physical mechanism at the origin of the fountaining event. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2122/5182 Titolo: Geochemical signatures of large active faults: The example of the 5 February 1783, Calabrian earthquake (southern Italy)<br/><br/>Autori: Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Five large earthquakes shook southern Calabria in February–March 1783. We focused on the first shock (Me 6.9),which occurred on 5 February in the Gioia Tauro Plain. Most investigators attribute the event to aW-dipping, highanglefault running at the base of the Aspromonte crystalline bedrock on the ESE side of the Plain (AspromonteFault). Other workers contend that the earthquake was generated by an E-dipping, low-angle blind fault (GioiaTauro Fault) similar to the adjacent Messina Straits Fault. In 1999–2000 we carried out four geochemical surveys inthe Gioia Tauro Plain with the aim of contributing to this debate with an independent line of evidence.We sampled240 groundwater sites and measured a suite of in-situ physical and chemical parameters. Our goal was to gainnew insight into the seismogenic source by identifying geochemical anomalies associated with the deepening ofthe hydrological circuits due to the presence of enhanced faulting/fracturing. The deep-fluid signatures are mainlyrepresented by temperature, salinity, total carbon and radon anomalies.We identified three zones of dominant deepfluid discharge: the Nicotera-Galatro area (along the Nicotera-Galatro portion of theNW-trending Nicotera-GioiosaJonica lineament), a small NW-SE trending area between Gioia Tauro and Seminara, and the coastline betweenRosarno and Palmi. This latter sector locates just above the upper edge of the hypothesised Gioia Tauro Fault. Mostof the geochemical anomalies are recorded around Rosarno, at the intersection between the Gioia Tauro Fault andthe Nicotera-Gioiosa Jonica lineament. In contrast, no evidence of groundwater deepening and active fracturingwas found along the Aspromonte Fault. Based on our new findings we updated the concepts of Geochemically ActiveFault Zone and Geochemical Interaction Fault Zone in view of the modern understanding of the hydro-mechanicalproperties of fault zones and the faulting mechanisms promoting fracture permeability in the crust. Thu, 15 Jan 2004 00:00:00 GMT