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  • 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry  (12)
  • 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas  (5)
  • Transport  (5)
  • Elsevier  (17)
  • American Meteorological Society  (5)
  • 2010-2014  (22)
  • 1995-1999
  • 1985-1989
  • 2011  (22)
Collection
Keywords
Publisher
Years
  • 2010-2014  (22)
  • 1995-1999
  • 1985-1989
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  • 1
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    Fluid circulation in the upper brittle crust: Thickness distribution, hydraulic transmissivity fluid inclusion and isotopic data of veins hosted in the Oligocene sandstones of the Macigno Formation in southern Tuscany, Italy (2011)
    Elsevier
    Details
    Publication Date: 2020-11-30
    Description: We present structural analysis, fluid inclusion data on calcite and quartz, and isotopic composition of calcite forming veins occurring in the upper crustal level and hosted in Oligocene sandstone in southern Tuscany (Italy). The veins have been analysed in two sites few kilometres apart, along well-exposed coastal cliffs and in an abandoned quarry. These two sites were at a different depths at the time of the vein formation with a Δh ~ 100 m. Structural analysis of veins provided estimations of stress ratio (Φ = (σ2 − σ3)/(σ1 − σ3)), driving stress ratio (R′ = (Pf − σ3)/(σ1 − σ3)) and fluid overpressure (ΔPo = Pf − σ3) at the time of vein formation. The estimated ΔPo is in the range of 42–103 MPa, Φ = 0.24 and R′ = 0.45, indicating that fluid pressure was higher than the intermediate principal stress at the time of veins formation. The veins' thickness (t) shows a clear power-law distribution (D = 1.8835 and R2 = 0.9762) in the lowermost site (coast) and a negative exponential distribution (a = 0.6943 and R2 = 0.9921) in the uppermost site (abandoned quarry). The vein thickness distributions have been used to compute the average transmissivity of the veins in the two sites. The computed transmissivity for the vein formation is ~ 10−4 m2 s−1, with higher values attained by the veins having negative exponential thickness distribution. Fluid inclusions studies highlighted that in both calcite and quartz, water-rich inclusions, with salinities of 2.2–4.3 wt.% NaCl equiv., and methane-rich inclusions were coevally trapped during fluid un-mixing processes. Thermogenic origin, from thermal maturation of organic matter present in the Macigno Formation, is proposed for methane. Whereas, the similarity between the δ18O (from 14.9 to 17.4‰) and δ13C (from −0.4 to −2.4‰) data of representative calcite veins and the isotopic composition (δ18O: 16.1‰, δ13C: −1.0‰) of host-rock carbonate component, indicates that the fluid which formed calcite was in isotopic equilibrium with the carbonates present in the Oligocene sandstones. The calculated pressure–temperature conditions during the formation of these inclusions are prevalently within the 40–145 MPa and 160–260 °C ranges. The highest pressure values approximate the lithostatic pressure (~ 120 MPa) computed from geological data and are coherent with a geothermal gradient ranges of 35–45 °C/km. Whereas, the lower pressure values are comparable with hydrostatic pressure conditions. The pressure range indicated by fluid inclusion data is also comparable with the fluid pressure estimated from structural analysis. The considerable pressure range can be related to pressure cycling between lithostatic and hydrostatic conditions as a consequence of fault-valve actions and rock fracturing with subsequent pressure recover due to self-sealing process.
    Description: Published
    Description: 118-138
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Vein systems ; Fluid type ; Fluid pressure ; Fluid inclusions ; Upper crust ; Tuscany ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Extreme methane deuterium, nitrogen and helium enrichment in natural gas from the Homorod seep (Romania) (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Methane (CH4) in terrestrial environments, whether microbial, thermogenic, or abiogenic, exhibits a large variance in C and H stable isotope ratios due to primary processes of formation. Isotopic variability can be broadened through secondary, post-genetic processes, such as mixing and isotopic fractionation by oxidation. The highest and lowest 13C and 2H (or D, deuterium) concentrations in CH4 found in various geologic environments to date, are defined as “natural” terrestrial extremes. We have discovered a new extreme in a natural gas seep with values of deuterium concentrations, δDCH4, up to+124‰that far exceed those reported for any terrestrial gas. The gas, seeping from the small Homorod mud volcano in Transylvania (Romania), also has extremely high concentrations of nitrogen (N92 vol.%) and helium (up to 1.4 vol.%). Carbon isotopes in CH4, C2H6 and CO2, and nitrogen isotopes in N2 indicate a primary organic sedimentary origin for the gas (a minor mantle component is suggested by the 3He/4He ratio, R/Ra~0.39). Both thermogenic gas formation modeling and Rayleigh fractionation modeling suggest that the extreme deuterium enrichment could be explained by an oxidation process characterised by a δDCH4 and δ13CCH4 enrichment ratio (ΔH/ΔC) of about 20, and may be accounted for by abiogenic oxidation mediated by metal oxides. All favourable conditions for such a process exist in the Homorod area, where increased heat flow during Pliocene–Quaternary volcanism may have played a key role. Finally we observed rapid variations (within 1 h) in C and H isotope ratios of CH4, and in the H2S concentrations which are likely caused by mixing of the deep oxidized CH4–N2–H2S–He rich gas with a microbial methane generated in the mud pool of one of the seeps. We hypothesize that the unusual features of Homorod gas can be the result of a rare combination of factors induced by the proximity of sedimentary organic matter, mafic, metal-rich volcanic rocks and salt diapirs,leading to the following processes: a) primary thermogenic generation of gas at temperatures between 130 and 175 °C; b) secondary alteration through abiogenic oxidation, likely triggered by the Neogene–Quaternary volcanism of the eastern Transylvanian margin; and c) mixing at the surface with microbial methane that formed through fermentation in the mud volcano water pool. The Homorod gas seep is a rare example that demonstrates how post-genetic processes can produce extreme gas isotope signatures (thus far only theorized), and that extremely positive δDCH4 values cannot be used to unambiguously distinguish between biotic and abiotic origin.
    Description: Published
    Description: 89-96
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; Deuterium ; Nitrogen ; Helium ; Seep ; Mud volcano ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Abiotic methane flux from the Chimaera seep and Tekirova ophiolites (Turkey): Understanding gas exhalation from low temperature serpentinization and implications for Mars (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The emission of abiotic methane (CH4) into the atmosphere from low temperature serpentinization in ophiolitic rocks is documented to date only in four countries, the Philippines, Oman, New Zealand, and Turkey. Serpentinization produces large amounts of hydrogen (H2) which in theory may react with CO2 or CO to form hydrocarbons (Fischer–Tropsch Type synthesis, FTT). Similar mechanisms have been invoked to explain the CH4 detected on Mars, so that understanding flux and exhalation modality of ophiolitic gas on Earth may contribute to decipher the potential degassing on Mars. This work reports the first direct measurements of gas (CH4, CO2) flux ever done on onshore ophiolites with present-day serpentinization. We investigated the Tekirova ophiolites at Çirali, in Turkey, hosting the Chimaera seep, a system of gas vents issuing from fractures in a 5000 m2 wide ophiolite outcrop. At this site at least 150–190 t of CH4 is annually released into the atmosphere. The molecular and isotopic compositions of C1–C5 alkanes, CO2, and N2 combined with source rock maturity data and thermogenic gas formation modelling suggested a dominant abiotic component (~80– 90%) mixed with thermogenic gas. Abiotic H2-rich gas is likely formed at temperatures below 50 °C, suggested by the low deuterium/hydrogen isotopic ratio of H2 (δDH2: −720‰), consistent with the low geothermal gradient of the area. Abiotic gas synthesis must be very fast and effective in continuously producing an amount of gas equivalent to the long-lasting (N2 millennia) emission of N100 t CH4 yr−1, otherwise pressurised gas accumulation must exist. Over the same ophiolitic formation, 3 km away from Chimaera, we detected an invisible microseepage of abiotic CH4 with fluxes from 0.07 to 1 g m−2 d−1. On Mars similar fluxes could be able to sustain the CH4 plume apparently recognised in the Northern Summer 2003 (104 or 105 t yr−1) over the wide olivine bedrock and outcrops of hydrated silicates in the Syrtis Major and Nili Fossae; just one seep like Chimaera or, more realistically, a weak, spatially sporadic microseepage, would be sufficient to maintain the atmospheric CH4 level on Mars.
    Description: Published
    Description: 96-104
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: abiotic methane ; seepage ; serpentinization ; ophiolites ; Mars ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 4
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    Fluid origin, gas fluxes and plumbing system in the sediment-hosted Salton Sea Geothermal System (California, USA) (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The Salton Sea Geothermal System (California) is an easily accessible setting for investigating the interactions of biotic and abiogenic geochemical processes in sediment-hosted hydrothermal systems. We present new temperature data and the molecular and isotopic composition of fluids seeping at the Davis-Schrimpf seep field during 2003–2008. Additionally, we show the first flux data for CO2 and CH4 released throughout the field from focused vents and diffuse soil degassing. The emitted gases are dominated by CO2 (~98%) and CH4 (~1.5%). By combining δ13CCO2 (as low as −5.4‰) and δ13CCH4 (−32‰to−17.6‰) with 3He/4He (R/RaN6) and δDCH4 values (−216‰to−150‰), we suggest, in contrast to previous studies, that CO2 may have a significant Sub-Continental Mantle source, with minimal crustal contamination, and CH4 seems to be a mixture of high temperature pyrolitic (thermogenic) and abiogenic gas. Water seeps show that δD and δ18O increase proportionally with salinity (Total Dissolved Solids in g/L) ranging from 1–3 g/L (gryphons) to 145 g/L (hypersaline pools). In agreement with elemental analyses, the isotopic composition of the waters indicate a meteoric origin, modified by surface evaporation, with little or no evidence of deep fossil or magmatic components. Very high Cl/Br (N3,000) measured at many seeping waters suggests that increased salinities result from dissolution of halite crusts near the seep sites. Gas flux measurements from 91 vents (pools and gryphons) give a conservative estimate of ~2,100 kg of CO2 and 11.5 kg of CH4 emitted per day. In addition soil degassing measured at 81 stations (20x20 m grid over 51,000 m2) revealed that 7,310 kg/d CO2 and 33 kg/d CH4 are pervasively released to the atmosphere. These results emphasise that diffuse gas emission from soil can be dominant (~75%) even in hydrothermal systems with large and vigorous gas venting. Sediment-hosted hydrothermal systems may represent an intermediate class of geologic methane sources for the atmosphere, with emission factors lower than those of sedimentary seepage in petroleum basins but higher than those of traditional geothermal-volcanic systems; on a global scale they may significantly contribute to the atmospheric methane budget.
    Description: Published
    Description: 67-83
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: Salton Sea Geothermal System ; hydrothermal seeps ; gas and water geochemistry ; flux measurements ; mantle ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 5
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    Magma vesiculation and infrasonic activity at Stromboli open conduit volcano (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Explosive activity at Stromboli is explained in terms of dynamics of large gas bubbles that ascend in the magma conduit and burst at the free surface generating acoustic pressure that propagates as infrasonic signals in the atmosphere. The rate and the amplitude of the infrasonic activity is directly linked to the rate and the overpressure of the bursting gas bubbles and thus reflects the rate at which magma column degasses under non-equilibrium pressure conditions. We investigate the link between explosive degassing and magma vesiculation by comparing the rate of infrasonic activity with the bubble size distributions (BSDs) of scoria clasts collected during several days of explosive activity at Stromboli. BSDs of scoria show a characteristic power law distribution, which reflect a gas bubble concentration mainly controlled by a combined process of bubble nucleation and coalescence. The cumulative distribution of the infrasonic pressure follows two power laws, indicating a clear separation between the frequent, but weak, bursting of small gas bubbles (puffing) and the more energetic explosions of large gas slugs. The exponents of power laws derived for puffing and explosive infrasonic activity show strongly correlated (0.96) changes with time indicating that when the puffing rate is high, the number of energetic explosions is also elevated. This correlation suggests that both puffing and explosive activity are driven by the same magma degassing dynamics. In addition, changes of both infrasonic power law exponents are very well correlated (0.92 with puffing and 0.87 with explosions) with variations of the BSD exponents of the scoria clasts, providing evidence of the strong interplay between scoria vesiculation and magma explosivity. Our analysis indicates that variable magma vesiculation regimes recorded in the scoria correlate with the event number and energy of the explosive activity. We propose that monitoring infrasound on active volcanoes may be an alternative way to look at the vesiculation process in open conduit systems.
    Description: Published
    Description: 274-280
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Strombolian activity ; magma vesiculation ; infrasound ; conduit dynamics ; explosive volcanism ; bubble size distribution ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 6
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    Societal need for improved understanding of climate change, anthropogenic impacts, and geo-hazard warning drive development of ocean observatories in European Seas (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Society’s needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised.
    Description: Published
    Description: 1-33
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: Seafloor and water columnobservatories ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate ; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions ; 03. Hydrosphere::03.01. General::03.01.08. Instruments and techniques ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 03. Hydrosphere::03.03. Physical::03.03.02. General circulation ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability ; 03. Hydrosphere::03.03. Physical::03.03.05. Instruments and techniques ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems ; 03. Hydrosphere::03.04. Chemical and biological::03.04.08. Instruments and techniques ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.03. Heat generation and transport ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 05. General::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 05. General::05.02. Data dissemination::05.02.02. Seismological data ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.02. Data dissemination::05.02.04. Hydrogeological data ; 05. General::05.08. Risk::05.08.01. Environmental risk ; 05. General::05.08. Risk::05.08.02. Hydrogeological risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    New evidence of mantle heterogeneity beneath the Hyblean Plateau (southeast Sicily, Italy) as inferred from noble gases and geochemistry of ultramafic xenoliths (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We analyzed major and trace elements, Sr and Nd isotopes in ultramafic xenoliths in Miocenic age Hyblean diatremes, along with noble gases of CO2-rich fluid inclusions hosted in the same products. The xenoliths consist of peridotites and pyroxenites, which are considered to be derived from the upper mantle. Although the mineral assemblage of peridotites and their whole-rock abundance of major elements (e.g., Al2O3 = 0.8–1.5 wt.%, TiO2 = 0.03–0.08 wt.%) suggest a residual character of the mantle, a moderate enrichment in some incompatible elements (e.g., LaN/YbN = 9–14) highlights the presence of cryptic metasomatic events. In this context a deep silicate liquid is considered the metasomatizing agent, which is consistent with the occurrence of pyroxenites as veins in peridotites. Both the Zr/Nb and 143Nd/144Nd ratios of the investigated samples reveal two distinct compositional groups: (1) peridotites with Zr/Nb ≈ 4 and 143Nd/144Nd ≈ 0.5129, and (2) pyroxenites with Zr/Nb ≈ 20 and 143Nd/144Nd ≈ 0.5130. The results of noble-gas analyses also highlight the difference between the peridotite and pyroxenite domains. Indeed, the 3He/4He and 4He/40Ar* ratios measured in the fluid inclusions of peridotites (respectively 7.0–7.4 ± 0.1 Ra and 0.5–8.2, where Ra is the atmospheric 3He/4He ratio of 1.38 × 10− 6) were on average lower than those for the pyroxenites (respectively 7.2–7.6 Ra and 0.62–15). This mantle heterogeneity is interpreted as resulting from a mixing between two end-members: (1) a peridotitic layer with 3He/4He ≈ 7 Ra and 4He/40Ar* ≈ 0.4, which is lower than the typical mantle ratio (~ 1–4) probably due to melt extraction events, and (2) metasomatizing mafic silicate melts that gave rise to pyroxenites characterized by 3He/4He ≈ 7.6 Ra, with a variable 4He/40Ar* due to degassing processes connected with the ascent of magma at different levels in the peridotite wall rock. The complete geochemical data set also suggests two distinct mantle sources for the xenolithic groups highlighted above: (1) a HIMU (high-μ)-type source for the peridotites and (2) a DM (depleted mantle)-type source for the pyroxenites.
    Description: Published
    Description: 70-81
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: restricted
    Keywords: noble gases ; mantle ; xenoliths ; fluid inclusions ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 8
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    Relations between deformation and upper crustal magma emplacement in laboratory physical models (2011)
    Elsevier
    Details
    Publication Date: 2020-05-28
    Description: This paper presents analogue models for the emplacement of granitic magmas in upper crustal levels with different mechanical layering during shortening, extension and strike–slip deformation. In particular, we investigated how a weak layer embedded in the upper brittle crust can control the level of magma emplacement. The adopted experimental setup was used to examine the control of soft rocks on the movement of magma through a deforming brittle crust. Model results indicate that the occurrence of a weak (soft) layer embedded in brittle (stiff) material has an impact on the level of magma emplacement. The level of emplacement during both extension and shortening was systematically deeper for models with a soft layer than for purely brittle models. During strike–slip deformation the magma pierced the surface in both purely brittle and brittle–ductile models.
    Description: Published
    Description: 139-146
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Mechanical layering of upper crust ; Magma emplacement ; Analogue modelling ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 9
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    Helium and argon isotopic compositions of mantle xenoliths from Tallante and Calatrava, Spain. (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We have analyzed by single-step crushing helium and argon isotopes in olivine and orthopyroxene from mantle xenoliths of Calatrava (CLV) in central Spain and Tallante (TL) in southeast Spain. The investigation focused on carefully selected samples previously characterized in terms of major and trace elements on both bulk rock and constituent minerals, and Sr and Nd isotopes on clinopyroxene separates. Six analyses were performed on protogranular spinel lherzolites from CLV, and 17 were performed on spinel harzburgites, lherzolites, and orthopyroxenites from TL. The 40Ar/36Ar ratio was between 296 and 622, indicating atmospheric contamination, which probably occurred during exposure to the surface. The helium-isotope ratio (3He/4He) ranged between 3.6 and 6.5 Ra in CLV samples and between 1.4 and 5.7 Ra in TL samples. There was a positive correlation between the 3He/4He and 4He/40Ar* ratios, possibly reflecting diffusive fractionation between 3He, 4He, and 40Ar within mantle sections interacting with ascending melts. However, the difference between the maximum 3He/4He ratios measured in CLV and TL appears to be related to significant differences in the metasomatic melts that affected the two sectors of the lithospheric mantle. In agreement with the findings of previous studies, the helium isotopes at CLV are compatible with metasomatism due to ascending HIMU-type asthenospheric melts. In contrast, the lower 3He/4He values recorded at TL suggest subduction-related metasomatic components that are possibly related to the Cenozoic subduction of the Betic system. Such event plausibly introduced crust-derived fluids that metasomatized the mantle wedge, slightly decreasing its 3He/4He value. Noble gases appear decoupled from other elements during these mantle processes, since comparatively low 3He/4He values have been recorded also in samples that are relatively unmetasomatized in terms of incompatible lithophile elements. We hypothesize a role for volatile-dominated, CO2-rich fluids progressively decoupling from the ascending metasomatic melts and migrating in the surrounding peridotite matrix to form a diffuse aureola enriched in noble gases.
    Description: Published
    Description: 18-26
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: reserved
    Keywords: noble gas ; xenoliths ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 10
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    Gas seepage from Tokamachi mud volcanoes, onshore Niigata Basin (Japan): Origin, post-genetic alterations and CH4–CO2 fluxes (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Methane and CO2 emissions from the two most active mud volcanoes in central Japan, Murono and Kamou (Tokamachi City, Niigata Basin), were measured in from both craters or vents (macro-seepage) and invisible exhalation from the soil (mini- and microseepage). Molecular and isotopic compositions of the released gases were also determined. Gas is thermogenic (d13CCH4 from 32.9‰ to 36.2‰), likely associated with oil, and enrichments of 13C in CO2 (d13CCO2 up to +28.3‰) and propane (d13CC3H8 up to 8.6‰) suggest subsurface petroleum biodegradation. Gas source and post-genetic alteration processes did not change from 2004 to 2010. Methane flux ranged within the orders of magnitude of 101–104 gmˉ2 dˉ1 in macro-seeps, and up to 446 g mˉ2 dˉ1 from diffuse seepage. Positive CH4 fluxes from dry soil were widespread throughout the investigated areas. Total CH4 emission from Murono and Kamou were estimated to be at least 20 and 3.7 ton aˉ1, respectively, of which more than half was from invisible seepage surrounding the mud volcano vents. At the macro-seeps, CO2 fluxes were directly proportional to CH4 fluxes, and the volumetric ratios between CH4 flux and CO2 flux were similar to the compositional CH4/CO2 volume ratio. Macro-seep flux data, in addition to those of other 13 mud volcanoes, supported the hypothesis that molecular fractionation (increase of the ‘‘Bernard ratio’’ C1/(C2 + C3)) is inversely proportional to gas migration fluxes. The CH4 ‘‘emission factor’’ (total measured output divided by investigated seepage area) was similar to that derived in other mud volcanoes of the same size and activity. The updated global ‘‘emission-factor’’ data-set, now including 27 mud volcanoes from different countries, suggests that previous estimates of global CH4 emission from mud volcanoes may be significantly underestimated.
    Description: Published
    Description: 348-359
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: restricted
    Keywords: Methane ; natural gas ; mud volcanoes ; seepage ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
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    Geochemical evidence for and characterization of CO2 rich gas sources in the epicentral area of the Abruzzo 2009 earthquakes (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We describe the results of a detailed hydrogeochemical campaign on the groundwater circulating in two regional aquifers located in the area of the Abruzzo 2009 earthquakes. The influx of deeply derived CO2 rich gases into the two aquifers is highlighted by the 13C isotopic composition of dissolved carbon species. The source of the gas is roughly localised beneath the epicentral area of the earthquakes where the presence of sources of fluids under high pressure is suggested by seismological investigations. The carbon isotopic-mass balance of the aquifers indicates that the amount of the deep CO2 dissolved and transported by the groundwaters is ~530 t/day. The chemical and isotopic composition of the gas entering the aquifers, named Abruzzo gas, has been derived by comparing the data measured in the springs with the results of a gas–water– rock reaction model, that simulates the evolution of the chemical and isotopic composition of groundwater affected by the input of a deeply-derived CO2 rich gas phase. The composition of Abruzzo gas is compared to that of 40 large gas emissions located in central Italy. The gas becomes progressively richer in radiogenic elements (4He and 40Ar) and in N2, from the volcanic complexes in the west to the Apennines in the east. The Abruzzo gas, in agreement with its location, well matches the composition of the gases emitted in the pre- Apennine region. These geochemical features, consistent with the structural setting of the region, indicate increasing residence times of the gas in the crust moving from west to east. In particular we suggest that the strong increase in radiogenic crustal gases reflects the occurrence of deep traps where the gas is stored at high pressures for a long time and that such high pressure gas pockets play a major role in the generation of Apennine earthquakes.
    Description: Published
    Description: 389–398
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: carbon dioxide ; Abruzzo earthquakes ; carbon isotopes ; helium isotopes ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
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  • 12
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    Atmospheric sources and sinks of volcanogenic elements in a basaltic volcano (Etna, Italy) (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: This study reports on the first quantitative assessment of the geochemical cycling of volcanogenic elements, from their atmospheric release to their deposition back to the ground. Etna’s emissions and atmospheric depositions were characterised for more than 2 years, providing data on major and trace element abundance in both volcanic aerosols and bulk depositions. Volcanic aerosols were collected from 2004 to 2007, at the summit vents by conventional filtration techniques. Precipitation was collected, from 2006 to 2007, in five rain gauges, at various altitudes around the summit craters. Analytical results for volcanic aerosols showed that the dominant anions were S, Cl, and F, and that the most abundant metals were K, Ca, Mg, Al, Fe, and Ti (1.5–50 lg m 3). Minor and trace element concentrations ranged from about 0.001 to 1 lg m 3. From such analysis, we derived an aerosol mass flux ranging from 3000 to 8000 t a 1. Most analysed elements had higher concentrations close to the emission vent, confirming the prevailing volcanic contribution to bulk deposition. Calculated deposition rates were integrated over the whole Etna area, to provide a first estimate of the total deposition fluxes for several major and trace elements. These calculated deposition fluxes ranged from 20 to 80 t a 1 (Al, Fe, Si) to 0.01–0.1 t a 1 (Bi, Cs, Sc, Th, Tl, and U). Comparison between volcanic emissions and atmospheric deposition showed that the amount of trace elements scavenged from the plume in the surrounding of the volcano ranged from 0.1% to 1% for volatile elements such as As, Bi, Cd, Cs, Cu, Tl, and from 1% to 5% for refractory elements such as Al, Ba, Co, Fe, Ti, Th, U, and V. Consequently, more than 90% of volcanogenic trace elements were dispersed further away, and may cause a regional scale impact. Such a large difference between deposition and emission fluxes at Mt. Etna pointed to relatively high stability and long residence time of aerosols in the plume.
    Description: Published
    Description: 7401-7425
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: trace elements ; volcanic plume chemistry ; bulk deposition ; Etna ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 13
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    Shelf circulation and cross-shelf transport out of a bay driven by eddies from an open-ocean current. Part I : interaction between a barotropic vortex and a steplike topography (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 889–910, doi:10.1175/2010JPO4496.1.
    Description: This paper examines interaction between a barotropic point vortex and a steplike topography with a bay-shaped shelf. The interaction is governed by two mechanisms: propagation of topographic Rossby waves and advection by the forcing vortex. Topographic waves are supported by the potential vorticity (PV) jump across the topography and propagate along the step only in one direction, having higher PV on the right. Near one side boundary of the bay, which is in the wave propagation direction and has a narrow shelf, waves are blocked by the boundary, inducing strong out-of-bay transport in the form of detached crests. The wave–boundary interaction as well as out-of-bay transport is strengthened as the minimum shelf width is decreased. The two control mechanisms are related differently in anticyclone- and cyclone-induced interactions. In anticyclone-induced interactions, the PV front deformations are moved in opposite directions by the point vortex and topographic waves; a topographic cyclone forms out of the balance between the two opposing mechanisms and is advected by the forcing vortex into the deep ocean. In cyclone-induced interactions, the PV front deformations are moved in the same direction by the two mechanisms; a topographic cyclone forms out of the wave–boundary interaction but is confined to the coast. Therefore, anticyclonic vortices are more capable of driving water off the topography. The anticyclone-induced transport is enhanced for smaller vortex–step distance or smaller topography when the vortex advection is relatively strong compared to the wave propagation mechanism.
    Description: Y. Zhang acknowledges the support of theMIT-WHOI Joint Programin Physical Oceanography, NSF OCE-9901654 and OCE-0451086. J. Pedlosky acknowledges the support of NSF OCE- 9901654 and OCE-0451086.
    Keywords: Transport ; Eddies ; Barotropic flow ; Topographic effects ; Vortices ; Currents ; Potential vorticity ; Rossby waves
    Repository Name: Woods Hole Open Access Server
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  • 14
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    On the role of eddies and surface forcing in the heat transport and overturning circulation in marginal seas (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 4844–4858, doi:10.1175/2011JCLI4130.1.
    Description: The factors that determine the heat transport and overturning circulation in marginal seas subject to wind forcing and heat loss to the atmosphere are explored using a combination of a high-resolution ocean circulation model and a simple conceptual model. The study is motivated by the exchange between the subpolar North Atlantic Ocean and the Nordic Seas, a region that is of central importance to the oceanic thermohaline circulation. It is shown that mesoscale eddies formed in the marginal sea play a major role in determining the mean meridional heat transport and meridional overturning circulation across the sill. The balance between the oceanic eddy heat flux and atmospheric cooling, as characterized by a nondimensional number, is shown to be the primary factor in determining the properties of the exchange. Results from a series of eddy-resolving primitive equation model calculations for the meridional heat transport, overturning circulation, density of convective waters, and density of exported waters compare well with predictions from the conceptual model over a wide range of parameter space. Scaling and model results indicate that wind effects are small and the mean exchange is primarily buoyancy forced. These results imply that one must accurately resolve or parameterize eddy fluxes in order to properly represent the mean exchange between the North Atlantic and the Nordic Seas, and thus between the Nordic Seas and the atmosphere, in climate models.
    Description: This study was supported by the National Science Foundation under Grants OCE-0726339 and OCE-0850416.
    Keywords: Eddies ; Forcing ; Meridional overturning circulation ; Transport ; North Atlantic Ocean ; Seas/gulfs/bays
    Repository Name: Woods Hole Open Access Server
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  • 15
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    Transport and dynamics of the Panay Sill overflow in the Philippine Seas (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 40 (2010): 2679–2695, doi:10.1175/2010JPO4395.1.
    Description: Observations of stratification and currents between June 2007 and March 2009 reveal a strong overflow between 400- and 570-m depth from the Panay Strait into the Sulu Sea. The overflow water is derived from approximately 400 m deep in the South China Sea. Temporal mean velocity is greater than 0.75 m s−1 at 50 m above the 570-m Panay Sill. Empirical orthogonal function analysis of a mooring time series shows that the flow is dominated by the bottom overflow current with little seasonal variance. The overflow does not descend below 1250 m in the Sulu Sea but rather settles above high-salinity deep water derived from the Sulawesi Sea. The mean observed overflow transport at the sill is 0.32 × 106 m3 s−1. The observed transport was used to calculate a bulk diapycnal diffusivity of 4.4 × 10−4 m2 s−1 within the Sulu Sea slab (575–1250 m) ventilated from Panay Strait. Analysis of Froude number variation across the sill shows that the flow is hydraulically controlled. A suitable hydraulic control model shows overflow transport equivalent to the observed overflow. Thorpe-scale estimates show turbulent dissipation rates up to 5 × 10−7 W kg−1 just downstream of the supercritical to subcritical flow transition, suggesting a hydraulic jump downstream of the sill.
    Description: This work was supported by the Office of Naval Research Grant N00014-09-1-0582 to Lamont-Doherty Earth Observatory of Columbia University; Grants ONR-13759000 and N00014-09-1-0582 to the Woods Hole Oceanographic Institution; Grant ONR-N00014-06-1-0690 to Scripps Institute of Oceanography; and a National Defense Science and Engineering Graduate Fellowship.
    Keywords: Transport ; Dynamics ; Topographic effects ; Currents ; Empirical orthogonal functions
    Repository Name: Woods Hole Open Access Server
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  • 16
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    Near-surface transport pathways in the north Atlantic Ocean : looking for throughput from the subtropical to the subpolar gyre (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 911–925, doi:10.1175/2011JPO4498.1.
    Description: Motivated by discrepancies between Eulerian transport estimates and the behavior of Lagrangian surface drifters, near-surface transport pathways and processes in the North Atlantic are studied using a combination of data, altimetric surface heights, statistical analysis of trajectories, and dynamical systems techniques. Particular attention is paid to the issue of the subtropical-to-subpolar intergyre fluid exchange. The velocity field used in this study is composed of a steady drifter-derived background flow, upon which a time-dependent altimeter-based perturbation is superimposed. This analysis suggests that most of the fluid entering the subpolar gyre from the subtropical gyre within two years comes from a narrow region lying inshore of the Gulf Stream core, whereas fluid on the offshore side of the Gulf Stream is largely prevented from doing so by the Gulf Stream core, which acts as a strong transport barrier, in agreement with past studies. The transport barrier near the Gulf Stream core is robust and persistent from 1992 until 2008. The qualitative behavior is found to be largely independent of the Ekman drift.
    Description: This work was supported by the National Science Foundation Grants CMG-82469600 and CMG-82579600 and by the Office of Naval Research Grant ONR-13108700.
    Keywords: Atlantic Ocean ; Transport ; Gyres ; Lagrangian circulation/transport ; Tracers ; Currents ; Meridional overturning circulation
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Transient effects of magma ascent dynamics along a geometrically variable dome-feeding conduit (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The transient dynamics of magma ascent during dome-forming eruptions were investigated and the effects of magma chamber pressure perturbations on eruption rate are illustrated. The numerical model DOMEFLOW, developed by the authors for this work, is applied to the problem. DOMEFLOW is a transient 1.5D isothermal two-phase flow model of magma ascent through an axisymmetric conduit of variable radius, which accounts for gas exsolution, bubble growth, crystallization induced by degassing, permeable gas loss through overlying magma and through conduit walls, as well as viscosity changes due to crystallization and degassing. For runs in which chamber pressure increases, the time required to reach the new steady state (transition time) is a complex function of the pressure perturbation, while for decreasing chamber pressure, transition time is a monotonic function of the magnitude of the pressure perturbation. The transition to the new steady state is mainly controlled by magma compressibility, travel time (time required for one parcel of magma to travel from chamber to surface), and the time over which the pressure perturbation occurs. Results of many runs (〉 300) were analyzed using dimensional analysis to reveal a general relationship which predicts the temporal evolution of magma effusion rate for a given sudden increase in chamber pressure; the product of the change in steady-state extrusion rate and the time required to reach the new steady state is linearly proportional to the normalized change in chamber pressure, the volume of the conduit, and the ratio of top and bottom conduit radii, and inversely proportional to the cubic root of volatile fraction. This relationship is used to interpret observed variations in two ongoing dome-building eruptions, the Soufrière Hills volcano, Montserrat, and Merapi volcano, Indonesia.
    Description: Published
    Description: 541-553
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: conduit dynamics ; conduit geometry ; magma ascent ; effusion rate ; computational model ; dome-building ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation
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  • 18
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    The pre-eruptive volatile contents of recent basaltic and pantelleritic magmas at Pantelleria (Italy) (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Pantelleria Island, located in the Sicily Channel Rift Zone (Italy), is the type locality for the peralkaline rhyolitic rocks called pantellerites. In the last 50 ka, after the large Green Tuff caldera-forming eruption, volcanic activity at Pantelleria has consisted of effusive and explosive eruptions mostly vented inside and along the rim of the caldera and producing silicic lava flows, lava domes and poorly dispersed pantelleritic pumice fall deposits. Basaltic cinder cones and lava flows are only present outside the caldera in the NW sector of the island. The most recent basaltic (Cuddie Rosse, 20 ka) and pantelleritic (Cuddia Randazzo and Cuddia del Gallo, 6 ka) pyroclastic products were sampled to investigate magmatic volatile contents through the study of melt inclusions. The melt inclusions in pyroxene and olivine phenocrysts of Cuddie Rosse scoriae have an alkali basalt composition. The dissolved volatiles comprise 0.9–1.6 wt.% H2O, several hundred ppm of CO2, 1600–2000 ppm of sulphur and 500–900 ppm of chlorine. The water–carbon dioxide couple gives a confining pressure 2 kbar prior to the eruption. This result indicates that episodes of magma ponding and crystallization occurred in the upper crust prior to eruption. The melt inclusions in feldspar, fayalite and aenigmatite phenocrysts of Cuddia del Gallo and Cuddia Randazzo pumice have a pantelleritic composition (Agpaitic Indices 1.3–2.1), up to 4.4 wt.% H2O, 8700 ppm Cl, 6000 ppm F, and CO2 below the detection limit. Sulphur averaging 420 ppm has been measured in Cuddia Randazzo melt inclusions. These data indicate relatively high volatile contents for these low-energy Strombolian-type eruptions. Melt inclusions in Cuddia del Gallo pumice show the most evolved composition (Agpaitic Indices 2–2.1) and the highest volatile content, in agreement with fluid saturation conditions in the magma chamber prior to the eruption. This implies a confining pressure of 1 kbar for the top of the pantelleritic reservoir. The composition of melt inclusions and mineralogical assemblage of Cuddia Randazzo pumice indicate that it has a lower evolutionary degree (Agpaitic Indices 1.3–1.8) and lower pre-eruptive Cl and H2O contents than Cuddia del Gallo pumice. An increase in pressure due to the exsolution of volatiles in the upper part of the pantelleritic reservoir may have triggered the Cuddia del Gallo explosive eruption. Evidence of widespread pre-eruptive mingling between trachytes and pantellerites suggests that the intrusion of trachytic magma into the pantelleritic reservoir likely played a major role in destabilizing the magma system just prior to the Cuddia Randazzo event.
    Description: Published
    Description: 191-201
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: reserved
    Keywords: Pantelleria ; peralkaline ; volatiles ; melt inclusions ; eruptive style ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 19
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    The feeding system of Agnano–Monte Spina eruption (Campi Flegrei, Italy): Dragging the past into present activity and future scenarios (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Magmatic processes triggering eruptions at Campi Flegrei caldera (southern Italy) and their relationships with the widespread emissions of fluids and caldera unrest episodes, are poorly constrained. The 4.1 ka B.P. Agnano–Monte Spina eruption, the reference event for a future large-size explosive eruption at Campi Flegrei, was investigated to shed light, through melt inclusion and isotope analyses, on the geochemical processes operating in the plumbing system. Chemical and isotopic data on whole rocks and glasses suggest that at least two magma batches mixed during the course of the eruption. Melt inclusion data highlight the pre-eruption storage conditions of two magmatic end-members. One end-member is like the less differentiated (shoshonitic) Campi Flegrei erupted magma, while the other could be a residual of the Neapolitan Yellow Tuff magma. Mixing between these two components was driven by a large gas phase which sustained the ascent of magmas of deep provenance. The H2O and CO2 contents in pyroxene-hosted melt inclusions yield entrapment pressures between 107 and 211 MPa, corresponding to depths between 4 and 8 km. The degassing trends reveal two extreme patterns. One pattern, already documented in the literature, is the volatile signature of poorly differentiated magmas ascending from more than 8 km depth, while the other is related to a gas-dominated magma, flushed by a CO2-rich gas phase partly released from the deep reservoir. This study provides a conceptual frame for unrest phases at Campi Flegrei, such as the 1982–84 event. Uplift phases can be related to closed-system ascent of magmas and fluids from more than 8 km depth, and their emplacement at shallow levels. This leads the shallow system to store, and then progressively release, the accumulated gas. In this view, both unrest episodes and eruptions could be strongly influenced by both the achievement of a critical upper limit of gas storage in the shallow magmatic reservoir and the stress and fracturing state of the roof rocks. The present results help to constrain the preeruptive conditions expected at Campi Flegrei caldera in case of a future large-size eruptive event.
    Description: Published
    Description: 135–147
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: reserved
    Keywords: Sr and Nd isotopes ; Melt inclusions ; Gas flushing ; Magma mixing ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 20
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    A CO2-rich gas trigger of explosive paroxysms at Stromboli basaltic volcano, Italy (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: In addition to rhythmic slug-driven Strombolian activity, Stromboli volcano occasionally produces discrete explosive paroxysms (2 per year on average for the most frequent ones) that constitute a major hazard and whose origin remains poorly elucidated. Partial extrusion of the volatile-rich feeding basalt as aphyric pumice during these events has led to consider their triggering by the fast ascent of primitive magma blobs from possibly great depth. Here I examine and discuss the alternative hypothesis that most of the paroxysms could be triggered and driven by the fast upraise of CO2-rich gas pockets generated by bubble foam growth and collapse in the sub-volcano plumbing system. Data for the SO2 and CO2 crater plume emissions are used to show that Stromboli's feeding magma may originally contain as much as 2 wt.% of carbon dioxide and early coexists with an abundant CO2-rich gas phase with high CO2/SO2 molar ratio (≥60 at 10 km depth below the vents, compared to ∼7 in time-averaged crater emissions). Pressure-related modelling indicates that the time-averaged crater gas composition and output are well accounted for by closed system decompression of the basalt–gas mixture until the volcano–crust interface (∼3 km depth), followed by open degassing and crystallization in the volcano conduits. However, both the low viscosity and high vesicularity of the basaltic magma permit bubble segregation and bubble foam growth at deep sill-like feeder discontinuities and at shallower physical boundaries (such as the volcano–crust interface) where the gasrich aphyric basalt interacts with the unerupted crystal-rich and viscous magma drained back from the volcano conduits. Gas pressure build-up and bubble foam collapse at these boundaries will intermittently trigger the sudden upraise of CO2-rich gas blobs that constitute the main driving force of the paroxysms. Deeper-sourced gas blobs, driving the most powerful explosions, will be the richest in CO2 and have highest CO2/SO2 ratios. This mechanism is shown to account well for the dynamic, seismic and petrologic features of Stromboli's paroxysms and, hence, to provide a potential alternative interpretation for their genesis and their forecasting. Enhanced bubble foam leakage prior to a paroxysm, or foam emptying in several steps, should lead indeed to precursory upstream of CO2-rich gas and increasing CO2/SO2 ratio in crater plume emissions. The recent detection of such signals prior to two explosions in December 2006 and March 2007 strongly supports this expectation and the model proposed in this study.
    Description: Published
    Description: 363–374
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: basaltic volcanoes ; magma degassing ; explosive paroxysms ; CO2 ; gas bubbles ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 21
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    Methane emissions from Earth’s degassing: Implications for Mars (2011)
    Elsevier
    Details
    Publication Date: 2022-02-16
    Description: The presence of methane on Mars is of great interest, since one possibility for its origin is that it derives from living microbes. However, CH4 in the martian atmosphere also could be attributable to geologic emissions released through pathways similar to those occurring on Earth. Using recent data on methane degassing of the Earth, we have estimated the relative terrestrial contributions of fossil geologic methane vs. modern methane from living methanogens, and have examined the significance that various geologic sources might have for Mars. Geologic degassing includes microbial methane (produced by ancient methanogens), thermogenic methane (from maturation of sedimentary organic matter), and subordinately geothermal and volcanic methane (mainly produced abiogenically). Our analysis suggests that not, vert, similar80% of the “natural” emission to the terrestrial atmosphere originates from modern microbial activity and not, vert, similar20% originates from geologic degassing, for a total CH4 emission of not, vert, similar28.0×107 tonnes year−1. Estimates of methane emission on Mars range from 12.6×101 to 57.0×104 tonnes year−1 and are 3–6 orders of magnitude lower than that estimated for Earth. Nevertheless, the recently detected martian, Northern-Summer-2003 CH4 plume could be compared with methane expulsion from large mud volcanoes or from the integrated emission of a few hundred gas seeps, such as many of those located in Europe, USA, Mid-East or Asia. Methane could also be released by diffuse microseepage from martian soil, even if macro-seeps or mud volcanoes were lacking or inactive. We calculated that a weak microseepage spread over a few tens of km2, as frequently occurs on Earth, may be sufficient to generate the lower estimate of methane emission in the martian atmosphere. At least 65% of Earth’s degassing is provided by kerogen thermogenesis. A similar process may exist on Mars, where kerogen might include abiogenic organics (delivered by meteorites and comets) and remnants of possible, past martian life. The remainder of terrestrial degassed methane is attributed to fossil microbial gas (not, vert, similar25%) and geothermal-volcanic emissions (not, vert, similar10%). Global abiogenic emissions from serpentinization are negligible on Earth, but, on Mars, individual seeps from serpentinization could be significant. Gas discharge from clathrate-permafrost destabilization should also be considered. Finally, we have shown examples of potential degassing pathways on Mars, including mud volcano-like structures, fault and fracture systems, and major volcanic edifices. All these types of structures could provide avenues for extensive gas expulsion, as on Earth. Future investigations of martian methane should be focused on such potential pathways.
    Description: Published
    Description: 182-195
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: restricted
    Keywords: Mars ; Methane ; Earth’s degassing ; Seepage ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 22
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    Continuous, array-based estimates of Atlantic Ocean heat transport at 26.5°N (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 2429–2449, doi:10.1175/2010JCLI3997.1.
    Description: Continuous estimates of the oceanic meridional heat transport in the Atlantic are derived from the Rapid Climate Change–Meridional Overturning Circulation (MOC) and Heatflux Array (RAPID–MOCHA) observing system deployed along 26.5°N, for the period from April 2004 to October 2007. The basinwide meridional heat transport (MHT) is derived by combining temperature transports (relative to a common reference) from 1) the Gulf Stream in the Straits of Florida; 2) the western boundary region offshore of Abaco, Bahamas; 3) the Ekman layer [derived from Quick Scatterometer (QuikSCAT) wind stresses]; and 4) the interior ocean monitored by “endpoint” dynamic height moorings. The interior eddy heat transport arising from spatial covariance of the velocity and temperature fields is estimated independently from repeat hydrographic and expendable bathythermograph (XBT) sections and can also be approximated by the array. The results for the 3.5 yr of data thus far available show a mean MHT of 1.33 ± 0.40 PW for 10-day-averaged estimates, on which time scale a basinwide mass balance can be reasonably assumed. The associated MOC strength and variability is 18.5 ± 4.9 Sv (1 Sv ≡ 106 m3 s−1). The continuous heat transport estimates range from a minimum of 0.2 to a maximum of 2.5 PW, with approximately half of the variance caused by Ekman transport changes and half caused by changes in the geostrophic circulation. The data suggest a seasonal cycle of the MHT with a maximum in summer (July–September) and minimum in late winter (March–April), with an annual range of 0.6 PW. A breakdown of the MHT into “overturning” and “gyre” components shows that the overturning component carries 88% of the total heat transport. The overall uncertainty of the annual mean MHT for the 3.5-yr record is 0.14 PW or about 10% of the mean value.
    Description: This research was supported by the U.S. National Science Foundation under Awards OCE0241438 and OCE0728108, by the U.K. RAPID Programme (RAPID Grant NER/T/S/2002/00481), and by the U.S. National Oceanic and Atmospheric Administration, as part of its Western Boundary Time Series Program.
    Keywords: Atlantic Ocean ; Meridonial overturning circulation ; Sea surface temperature ; Transport ; Anomalies
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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