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  • 04. Solid Earth::04.08. Volcanology::04.08.01. Gases  (8)
  • 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations  (5)
  • Elsevier  (13)
  • American Geophysical Union
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • Public Library of Science
  • 2005-2009  (13)
  • 2007  (13)
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Keywords
Publisher
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  • 2005-2009  (13)
Year
  • 1
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    A new computational approach to reduce the signal from continuously recording gravimeters for the effect of atmospheric temperature (2007)
    Elsevier
    Details
    Publication Date: 2017-04-03
    Description: The experience of several authors has shown that continuous measurements of the gravity field, accomplished through spring devices, are strongly affected by changes of the ambient temperature. The apparent, temperature-driven, gravity changes can be up to one order of magnitude higher than the expected changes of the gravity field. Since these effects are frequency-dependent and instrument-related, they must be removed through non-linear techniques and in a case-by-case fashion. Past studies have demonstrated the effectiveness of a Neuro-Fuzzy algorithm as a tool to reduce continuous gravity sequences for the effect of external temperature changes. In the present work, an upgraded version of this previously employed algorithm is tested against the signal from a gravimeter, which was installed in two different sites over consecutive 96-day and 163-day periods. The better performance of the new algorithm with respect to the previous one is proven. Besides, inferences about the site and/or seasonal dependence of the model structure are reported.
    Description: Published
    Description: 247–256
    Description: reserved
    Keywords: Gravimeters ; Exogenous parameter compensantion ; Neuro-Fuzzy algorithm ; Site effects ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations ; 05. General::05.01. Computational geophysics::05.01.01. Data processing
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    A data sequence acquired at Mt. Etna during the 2002–2003 eruption highlights the potential of continuous gravity observations as a tool to monitor and study active volcanoes (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: A 2.5-month long gravity sequence, encompassing the starting period of the 2002–2003 Etna eruption and coming from a summit station only 1 km away from the new fractures, is presented and discussed. The sequence comprises four hours-long anomalies that have a great chance to reflect mass redistributions linked to the ensuing activity. In particular, the start of the eruptive activity on the northeastern flank was marked by a gravity decrease as strong as about 400 microGal, which reverted soon afterwards. This strong decrease/increase anomaly is interpreted as the opening, by tectonic forces, of a fracture system along the Northeastern Rift of Mt. Etna, followed by an intrusion of magma from the central conduit to the new fractures. They were used by the intruding magma as a path to the eruptive vents at lower elevations. Afterwards, on three occasions, in November and December 2002, 6–12 h-lasting gravity decreases, with amplitude ranging between 10 and 30 microGal, were observed simultaneously with increases in the amplitude of the volcanic tremor from four seismic stations. A correlation analysis, between the gravity signal and the overall spectral amplitude of each tremor sequence is performed over the 7 November–9 December period. A marked anti-correlation is found over each contemporaneous gravity decrease/tremor increase, while, over the rest of the investigated period, the correlation is negligible. Accordingly, a joint source is inferred to have acted during the occurrence of the three common anomalies. On the grounds of some volcanological observations spanning the period covered by our analysis, we propose the temporary accumulation of a gas cloud at some level within the plumbing system of the volcano to have acted as a joint source. The present work is a further evidence of the potential of continuous gravity observations as a tool to monitor and study active volcanoes and encourages their employment in spite of the difficulty of running spring gravimeters in a continuous fashion under the adverse conditions normally encountered on the summit zone of an active volcano.
    Description: Published
    Description: 320–329
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Gravity anomalies ; Magma intrusion ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Focused and diffuse effluxes of CO2 from mud volcanoes and mofettes south of Mt. Etna (Italy) (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Several sites with anomalous emissions of carbon dioxide were investigated in the region south of Mt. Etna volcano in order to assess the types of emission (focused and/or diffuse), their surface extension and the total output of CO2. Most of the studied emissions are located on the southwest boundary of Mt. Etna, near the town of Paternò. They consist of three mud volcanoes (known as Salinelle), one spring with bubbling gas (Acqua Grassa) and one area of diffuse degassing (Peschería). Another site (Naftía Lake) with remarkable gas emissions (bubbling gas into a lake as well as adjacent areas of diffuse soil degassing) is located further southwest of Mt. Etna in an area of extinct Quaternary volcanism on the northwest margin of Hyblean Mts. In all of these areas the origin of the highest CO2 emissions is clearly magmatic, and degassing to the atmosphere occurs mostly through tectonic structures, probably at a regional scale. The magmatic source that feeds anomalous degassing in the above areas is likely to be the same that feeds volcanic activity at Mt. Etna. Focused degassing was measured at each emission vent using devices that measure the air speed, whereas diffuse soil degassing was measured using the accumulation chamber method. In total, 712 measurements were carried out (146 in focused degassing vents, 566 on diffuse degassing areas). Single CO2 output values ranged from 1.8 10−5 to 1.68 kg s−1. In the case of diffuse degassing areas, statistical analyses allowed to discriminate between biogenic CO2 and CO2 deriving from a magmatichydrothermal source. Only the efflux values from the latter source were considered in the output estimates. The total estimated output thus obtained was about 2.61 kg s−1, relevant to a total surface of about 146,500 m2 (which includes only the magmatic CO2 emissions). This value is comparable with that of most non-volcanic emissions from geothermal and/or faulted areas of centralsouthern Italy, as well with the CO2 output from some of the volcanic areas of Italy.
    Description: Istituto Nazionale di Geofisica e Vulcanologia; Dipartimento per la Protezione Civile.
    Description: Published
    Description: 46–63
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; mud volcanoes ; soil CO2 effluxes ; magmatic degassing ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 4
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    Environmental impact of magmatic fluorine emission in the Mt. Etna area (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The sustained and uninterrupted plume degassing at Mount Etna volcano, Southern Italy, represents the troposphere’s most prominent natural source of fluorine. Of the ~ 200 Mg of fluorine (as HFg) emitted daily by the volcano, 1.6±2.7 Mg are deposited by wet and dry deposition. Fluorine-deposition via volcanic ash, here characterised for the first time, can be quite significant during volcanic eruptions (i.e. 60 Mg of fluorine were deposited during the 2001 eruption through volcanic ash, corresponding to ~ 85% of the total fluorine deposition). Despite the fact that these depositions are huge, the fate of the deposited fluorine and its impact on the environment are poorly understood. We herein present original data on fluorine abundance in vegetation (Castanea Sativa and Pinus Nigra) and andosoils from the volcano’s flank, in the attempt to reveal the potential impact of volcanogenic fluorine emissions. Fluorine contents in chestnut leaves and pine needles are in the range 1.8-35 µg/g and 2.1-74 µg/g respectively; they exceed the typical background concentrations in plants growing in rural areas, but fall within the lower range of typical concentrations in plants growing near high fluorine anthropogenic emission sources. The rare plume fumigations on the lower flanks of Mt Etna (distance 〉 4 km from summit craters) are probably the cause of the “undisturbed” nature of Etnean vegetation: climatic conditions, which limit the growth of vegetation on the upper regione deserta, are a natural limit to the development of more severe impacts. High fluorine contents, associated with visible symptoms, were only measured in pine needles at three sites, located near recently-active (2001 to 2003) lateral eruptive fractures. Total fluorine contents (FTOT) in the Etnean soils have a range of 112-341 µg/g, and fall within the typical range of undisturbed soils; fluorine extracted with distilled water (FH2O) have a range of 5.1 to 61 µg/g and accounts for 2-40 % of FTOT. FH2O is higher in topsoils from the eastern flank (downwind), while it decreases with depth in soil profiles and on increasing soil grain size (thereby testifying to its association with clay-mineral-rich, fine soil fractions). The fluorine adsorption capacity of the andosoils acts as a natural barrier that protects the groundwater system.
    Description: Published
    Description: 87-101
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; Fluorine ; environmental volcanology ; impact of volcanic F ; soils ; vegetation ; volcanic ash ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 05. General::05.08. Risk::05.08.01. Environmental risk
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  • 5
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    Gas geochemistry as a tool to investigate the Earth's degassing through volcanic and seismic areas: The soul of the 8th International Conference on Gas Geochemistry (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Introduction of a special issue of the journal
    Description: no abstract
    Description: Published
    Description: 1-4
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Earth's degassing ; volcanic areas ; seismic areas ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Ground deformation and gravity changes on the Island of Pantelleria in the geodynamic framework of the Sicily Channel (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The island of Pantelleria is an active volcano located in the Sicily Channel (Southern Italy), in the middle of a continental rift system. Since the 1980s the island was periodically surveyed by using geodetic techniques (EDM, levelling, GPS and high precise gravimetry) to monitor the regional and local volcanic dynamics. Gravity data, collected between 1990 and 1998, show short and long wavelength changes due to the combined effect of shallow and deep sources. They reflect, to some degree, the structural setting of the island as delineated by the Bouguer anomaly field, which indicates that the island is broken up into two main basement blocks. The latter are bordered by two lineaments, probably regional faults related to the global geodynamics of the Sicily Channel Rift Zone. Moreover, the inverse correlation between the gravity and altimetric variations suggests that: i) Pantelleria is kinematically divided in two blocks; ii) the observed behaviour is strongly influenced by the geodynamics of the Sicily Channel. A new interpretation of the fully reprocessed data sets is presented, focusing on the spatial–temporal features of the horizontal ground deformation and gravity changes compared to the Bouguer anomaly and altimetric data. This leads to conclude that volcanism on the island has been probably strongly influenced by the global geodynamics of the Sicily Channel, and future eruptions are most likely to occur at the structural boundary separating the two blocks.
    Description: Published
    Description: 146– 162
    Description: reserved
    Keywords: Pantelleria ; geodesy ; deformation ; gravity ; volcanism ; geodynamics ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Evaluation of carbon isotope fractionation of soil CO2 under an advective–diffusive regimen: A tool for computing the isotopic composition of unfractionated deep source (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: A physical model based on the advective–diffusion theory was developed in order to describe the mixing between a deep gas source and the atmosphere. The model was used to predict the isotopic fractionation of carbon in soil CO2. Gas samples were collected at different depths in areas characterized by different geological settings and CO2 fluxes. The relative theoretical and experimental isotopic profiles were compared and a good agreement was found. These profiles show how the isotopic composition of CO2 changes through the upper few decimeters of soil and how the amount of the isotopic fractionation is strongly influenced by soil CO2 flux. Finally, the model was used to derive the carbon isotopic composition of unfractioned deep CO2 source for all the investigated sites
    Description: Published
    Description: 3016–3027
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Carbon isotope fractionation ; soil degassing ; gas transport ; D13C(CO2) ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 8
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    Analysis of simultaneous gravity and tremor anomalies observed during the 2002-2003 Etna eruption (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: In this paper we discuss the data collected by a large aperture array of broadband seismometers and a continuously recording gravity station during the 2002–2003 eruption of Etna volcano (Italy). Seismic signals recorded during the eruption are dominated by volcanic tremor whose energy spans the 0.5–5 Hz frequency band. On three different occasions (12 November, 19–20 November and 8–9 December 2002), we observed marked increases of the tremor amplitude (up to a factor of 4), which occurred simultaneously with gravity decreases (up to 30 μGal). The three concurrent gravity/tremor anomalies last 6 to 12 hours and terminate with rapid (up to 2 hours) changes, after which the signals return back to their original levels. Based on volcanological observations encompassing the simultaneous anomalies, we infer that the accumulation of a gas cloud at some level in the conduit plexus feeding a new eruptive vent could have acted as a joint source. This study highlights the potential of joint gravity–seismological analyses to both investigate the internal dynamic of a volcano and to improve the confidence of volcanic hazard assessment.
    Description: Published
    Description: 616-629
    Description: reserved
    Keywords: Etna ; volcanic tremor ; gravity changes ; foam layer ; 04. Solid Earth::04.03. Geodesy::04.03.04. Gravity anomalies ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    S–Cl–F degassing pattern of water-rich alkali basalt: Modelling and relationship with eruption styles on Mount Etna volcano (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Our knowledge of the degassing pattern of sulphur, chlorine and fluorine during ascent and eruption of basaltic magmas is still fragmental and mainly limited to water-poor basalts. Here we model and discuss the pressure-related degassing behaviour of S, Cl and F during ascent, differentiation and extrusion of H2O–CO2-rich alkali basalt on Mount Etna (Sicily) as a function of eruptive styles. Our modelling is based on published and new melt inclusion data for dissolved volatiles (CO2, H2O, S, Cl, F) in quenched explosive products from both central conduit (1989–2001) and lateral dyke (2001 and 2002) eruptions. Pressures are obtained from the dissolved H2O and CO2 concentrations, and vapour–melt partition coefficients of S, Cl and F are derived from best fitting of melt inclusion data for each step of magma evolution. This allows us to compute the compositional evolution of the gas phase during either open or closed system degassing and to compare it with the measured composition of emitted gases. We find that sulphur, chlorine and fluorine begin to exsolve at respective pressures of ∼140 MPa, ∼100 MPa and ≤10 MPa during Etna basalt ascent and are respectively degassed at 〉95%, 22–55%, and ∼15% upon eruption. Pure open system degassing fails to explain gas compositions measured during either lateral dyke or central conduit eruptions. Instead, closed-system ascent and eruption of the volatile-rich basaltic melt well accounts for the time-averaged gas composition measured during 2002-type lateral dyke eruptions (S/Cl molar ratio of 5±1, 35% bulk Cl loss). Extensive magma fragmentation during the most energetic fountaining phases enhances Cl release (55%) and produces a lower S/Cl ratio of 3.7, as actually measured. Comparatively slower magma rise in the central conduits of Etna favours both sulphide saturation of the melt and greater chlorine release (55%), resulting in a distinct S/Cl evolution path and final ratio in eruptive gas. In both eruption types, any previous bubble–melt separation at depth leads to increased S/Cl and S/F ratios in emitted gas. High S/Cl ratios measured during some discrete eruptive events can thus be explained by transitions from closed (deep) to open (shallow) system degassing, with differential gas transfer extending down to ∼2 km depth below the vents. This depth coincides with the base of the volcanic pile where structural discontinuities and the high magma vesicularity (60%) may favour separate gas flow. Finally, the excess S–Cl–F gas discharge through Etna summit craters during non-eruptive periods requires a mixed supply from shallow magma degassing in the volcanic conduits and deeper-derived SO2-rich bubbles from the sub-volcano plumbing system. Our modelling provides a useful reference framework for interpreting the monitored variations of S, Cl and F in Mount Etna gas emissions as a function of volcanic activity. More broadly, the observations made for S, Cl and F degassing on Etna may apply to other basaltic volcanoes with water-rich magmas, such as in arcs.
    Description: Published
    Description: 772-786
    Description: reserved
    Keywords: Mt Etna ; volatiles ; magma degassing ; eruptive mechanisms ; modelling ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    On the capability of recording gravity stations to detect signals coming from volcanic activity: the case of Vesuvius. (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The goal of this paper is to describe how continuous gravity measurements can improve the geophysical monitoring of a volcano. Here the experience of 15 yr in continuous gravity on Vesuvius is presented. A wide set of dynamic phenomena (i.e. geodynamics, seismicity, volcanic activity) can produce temporal gravity changes, with a spectrum varying from short (1–10 s) to longer (more than 1 yr) periods. An impending eruption, for instance, is generally associated with the ascent of magma producing changes in the density distribution at depth, and leading to ground deformation and gravity changes observed at surface. The amplitude of such gravity variations is often quite small, on the order of 10 9–10 8 g (10–102 nm/s2; 1–10 AGal), where g is the mean value of normal gravity (9.806 199 203 m/s2), so their detection requires instruments with high sensitivity and stability, providing high quality data. Natural, man-made and instrumental sources are present on the gravity records affecting the Signal to Noise Ratio. Such effects may hide the subtle volcanic signals. The main natural noise is due to ocean–atmosphere dynamics and seismic activity. New approaches to model the instrumental response of mechanical gravity sensors (based on the inter-comparison among superconducting, mechanical and absolute gravimeters) and to investigate the temporal trends of the instrumental sensitivity are proposed. In fact, variations of the calibration factors can be considered the main cause preventing the repeatability of highprecision gravity measurements and inducing phase and amplitude perturbations in recorded gravity signals. A modelling of the background gravity noise level was performed at the Vesuvius station. Moreover, the bfar fieldQ effects produced by large earthquakes on the gravity station have been also investigated. Finally, the time dependent behaviour of the tidal gravimetric factors, the non-stationary components of the gravity field detected at Vesuvius and the results of absolute and relative gravity measurements are interpreted in the framework of its present-day dynamics, mainly characterized by the low level of seismicity, small ground deformation, gravity changes and moderate gas emission.
    Description: Published
    Description: 270– 282
    Description: reserved
    Keywords: Vesuvius ; gravity ; record ; volcanic processes ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 11
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    Physics, chemistry and rheology of silicate melts and glasses (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Knowledge of the physical, chemical and thermodynamic properties of silicate melts and glasses is required to understand magma formation and evolution at all scales of observation. As is illustrated by the papers published in this special issue of Chemical Geology, there is a complex interplay between microscopic and macroscopic features. Whereas determining the microscopic structure of glasses and melts is useful to understand how macroscopic properties vary with pressure, temperature and composition, studies of macroscopic properties in turn put strong constraints on which microscopic aspects are actually relevant to a given problem. In this issue this approach is successfully applied to a variety of topics which range from melt rheology to volatile solubility or from spectroscopic investigations of silicate speciation to computer simulation studies of melt/glass structure. These papers were originally presented and discussed in April 2005 at the Vienna meeting of the European Union of Geosciences. They represent an up-to-date overview of current research in the field, ranging from classical approaches to new science and technology solutions which will help expand our research possibilities. We thank the Chemical Geology staff and all contributors and colleagues who made this volume possible.
    Description: Published
    Description: 1
    Description: open
    Keywords: NONE ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 12
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    Natural emissions of methane from geothermal and volcanic sources in Europe (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: It has recently been demonstrated that methane emission from lithosphere degassing is an important component of the natural greenhouse-gas atmospheric budget. Globally, the geological sources are mainly due to seepage from hydrocarbon-prone sedimentary basins, and subordinately from geothermal/volcanic fluxes. This work provides a first estimate of methane emission from the geothermal/volcanic component at European level. In Europe, 28 countries have geothermal systems and at least 10 countries host surface geothermal manifestations (hot springs, mofettes, gas vents). Even if direct methane flux measurements are available only for a few small areas in Italy, a fair number of data on CO2, CH4 and steam composition and flux from geothermal manifestations are today available for 6 countries (Czech Republic, Germany, Greece, Iceland, Italy, Spain). Following the emission factor and area-based approach, the available data have been analyzed and have led to an early and conservative estimate of methane emission into the atmosphere around 10,000 ton/yr (4000–16,000 ton/yr), basically from an area smaller than 4000 km2, with a speculative upper limit in the order of 105 ton/yr. Only 4–18% of the conservative estimate (about 720 ton/yr) is due to 12 European volcanoes, where methane concentration in volcanic gases is generally in the order of a few tens of ppmv. Volcanoes are thus not a significant methane source. While the largest emission is due to geothermal areas, which may be situated next to volcanoes or independent. Here inorganic synthesis, thermometamorphism and thermal breakdown of organic matter are substantial. Methane flux can reach hundreds of ton/yr from small individual vents. Geothermal methane is mainly released in three countries located in the main high heat flow regions: Italy, Greece, and Iceland. Turkey is likely a fourth important contributor but the absolute lack of data prevents any emission estimate. Therefore, the actual European geothermal–volcanic methane emission could be easily projected to the 105 ton/yr levels, reaching the magnitude of some other natural sources such as forest fires or wild animals.
    Description: Published
    Description: 76-86
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; volcanoes ; Geothermal vents ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 13
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    Accidental gas emission from shallow pressurized aquifers at Alban Hills volcano (Rome, Italy): Geochemical evidence of magmatic degassing? (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Recent studies suggested that Alban Hills (Rome) is a quiescent and not an extinct volcano, as it produced Holocene eruptions and several lahars until Roman times by water overflow fromthe Albano crater lake. Alban Hills are presently characterized by high PCO2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover. Gas consists mostly of CO2 with minor H2S and the diffuse CO2 soil flux is locally very high. Accidental gas blowouts, occurred during shallow well drillings (tens to hundreds m depth) in zones with no surface gas manifestations, indicate the presence of gas pressurized aquifers confined underneath impermeable layers, within both the volcanic rock pile and the underlying Pleistocene loose sediments. Degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the Mesozoic carbonate basement, hosting the main aquifer. Carbon isotopic composition (δ13CCO2) suggests that CO2 is at least partly originated by thermal decarbonation of these limestones. 3He/4He isotopic ratio of the gas (up to 1.9 Ra) is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the Alban Hills volcanic products, indicating a possible magmatic source for the gas. Low R/Ra values, compared to MORB and island arc magmas, are characteristic of the potassic Roman Comagmatic Province and reflect a deep involvement of crustal material in the magma genesis. The lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains.
    Description: Published
    Description: 5-16
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Alban Hills ; magma degassing ; CO2 fluxes ; gas blowouts ; C and He isotopes ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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