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Iacono Marziano, Giada
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Iacono Marziano, Giada
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Iacono-Marziano, Giada
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- PublicationOpen AccessRole of non-mantle CO2 in the dynamics of volcano degassing: The Mount Vesuvius example(2009-04)
; ; ; ; ; ;Iacono Marziano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Gaillard, F.; CNRS, INSU, Université d’Orléans, Institut des Sciences de la Terre d’Orléans (ISTO), UMR 6113 CNRS, Orléans Cedex 2, France ;Scaillet, B.; CNRS, INSU, Université d’Orléans, Institut des Sciences de la Terre d’Orléans (ISTO), UMR 6113 CNRS, Orléans Cedex 2, France ;Pichavant, M.; CNRS, INSU, Université d’Orléans, Institut des Sciences de la Terre d’Orléans (ISTO), UMR 6113 CNRS, Orléans Cedex 2, France ;Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; Mount Vesuvius, Italy, quiescent since A.D. 1944, is a dangerous volcano currently characterized by elevated CO2 emissions of debated origin. We show that such emissions are most likely the surface manifestation of the deep intrusion of alkalic-basaltic magma into the sedimentary carbonate basement, accompanied by sidewall assimilation and CO2 volatilization. During the last eruptive period (1631–1944), the carbonate-sourced CO2 made up 4.7–5.3 wt% of the vented magma. On a yearly basis, the resulting CO2 production rate is comparable to CO2 emissions currently measured in the volcanic area. The chemical and isotopic composition of the fumaroles supports the predominance of this crust-derived CO2 in volatile emissions at Mount Vesuvius.208 393 - PublicationOpen AccessThe role of melt composition on aqueous fluid vs. silicate melt partitioning of bromine in magmas(2018)
; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;Volcanogenic halogens, in particular bromine, potentially play an important role in the ozone depletion of the atmosphere. Understanding bromine behaviour in magmas is therefore crucial to properly evaluate the contribution of volcanic eruptions to atmospheric chemistry and their environmental impact. To date, bromine partitioning between silicate melts and the gas phase is very poorly constrained, with the only relevant experimental studies limited to investigation of synthetic melt with silicic compositions. In this study, fluid/melt partitioning experiments were performed using natural silicate glasses with mafic, intermediate and silicic compositions. For each composition, experiments were run with various Br contents in the initial fluid (H2O–NaBr), at T–Pconditions representative of shallow magmatic reservoirs in volcanic arc contexts (100–200MPa, 900–1200◦C). The resulting fluid/melt partition coefficients (DBrf/m) are: 5.0 ±0.3 at 1200◦C–100MPa for the basalt, 9.1 ±0.6 at 1060◦C–200MPa for the andesite and 20.2 ±1.2 at 900◦C–200MPa for the rhyodacite. Our experiments show that DBrf/mincreases with increasing SiO2content of the melt (as for chlorine) and suggest that it is also sensitive to melt temperature (increase of DBrf/mwith decreasing temperature). We develop a simple model to predict the S–Cl–Br degassing behaviour in mafic systems, which accounts for the variability of S–Cl–Br compositions of volcanic gases from Etna and other mafic systems, and shows that coexisting magmatic gas and melt evolve from S-rich to Cl–Br enriched (relative to S) upon increasing degree of degassing. We also report first Br contents for melt inclusions from Etna, Stromboli, Merapi and Santorini eruptions and calculate the mass of bromine available in the magma reservoir prior to the eruptions under consideration. The discrepancy that we highlight between the mass of Br in the co-existing melt and fluid prior to the Merapi 2010 eruption (433 and 73 tons, respectively) and the lack of observed BrO (from space) hints at the need to investigate further Br speciation in ‘ash-rich’ volcanic plumes. Overall, our results suggest that the Br yield into the atmosphere of cold and silicic magmas will be much larger than that from hotter and more mafic magmas.264 33 - PublicationRestrictedGeochemical evidence for mixing between fluids exsolved at different depths in the magmatic system of Mt Etna (Italy)(2012)
; ; ; ; ; ;Paonita, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Caracausi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Iacono Marziano, G.; CNRS-ISTO Orleans ;Martelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Rizzo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; ; ; ; A 4-year geochemical survey of some fumaroles at the Voragine summit crater of Mt Etna was performed in combination with synchronous monitoring of peripheral gas emissions at the base of the volcano. This was the first geochemical study at Mt Etna to have included the abundances of Ar, He, and C isotopes. Once the effects of postmagmatic shallow processes were identified and quantitatively removed, the He–Ar–CO2 systematics of the Voragine crater fumaroles and peripheral gas emissions described the same degassing path. Combining the carbon-isotope composition with information about noble gases provided evidence that the crater fumaroles are fed from a two-endmember mixture composed of a deep member coming from pressures between 200 and 400 MPa (depending on time), and a shallower one exsolved at 130 MPa. Similar mixing processes probably also occur in gases from peripheral vents. The simultaneous assessment of d13CCO2 and He/Ar values of crater fumaroles over time has identified simple changes in the mixing proportion between the two endmembers and, moreover, periods during which the exsolution pressure of the deep fluid increased. These periods seem to be linked to pre-eruptive phases of the volcano. The identified open-system degassing processes are indicative of efficient bubble–melt decoupling at depth, whereas the mixing process requires a convective transfer of the deeply exsolved fluids toward shallower levels of magma where further vapor is exsolved. In agreement with the most recent geophysical and petrological data from Mt Etna, these observations allow inferences about a deep portion of the plumbing system (5 to 12 km b.s.l.), comprising sill-like reservoirs connected by small vertical structures, and a main reservoir at 2–3 km b.s.l. that is probably fluxed by magmatic volatiles. 2012 Elsevier Ltd. All rights reserved.231 26 - PublicationOpen AccessCarbonatite Melts and Electrical Conductivity in the Asthenosphere(2008-11)
; ; ; ; ; ;Gaillard, F.; CNRS/INSU, Université d'Orléans, Université François Rabelais - Tours, ;Malki, M.; CEMHTI-CNRS, UPR3079, 1D avenue de la Recherche Scientifique, 45071 Orléans cedex2, ;Iacono Marziano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Pichavant, M.; CNRS/INSU, Université d'Orléans, Université François Rabelais - Tours, ;Scaillet, B.; CNRS/INSU, Université d'Orléans, Université François Rabelais - Tours,; ; ; ; Electrically conductive regions in the Earth mantle have been interpreted to reflect the presence of either silicate melt or water dissolved in olivine. On the basis of laboratory measurements we show that molten carbonates have electrical conductivities that are 3 orders of magnitude higher than those of molten silicate and 5 orders of magnitude higher than those of hydrated olivine. High conductivities in the asthenosphere probably indicate the presence of small amounts of carbonate melt in peridotite and can therefore be interpreted in terms of carbon concentration in the upper mantle. We show that the conductivity of the Oceanic asthenosphere can be explained by 0.1 volume % of carbonatite melts on average, which agrees with the CO2 content of Mid Ocean Ridge Basalts.151 330 - PublicationRestrictedA new set of standards for in–situ measurement of bromine abundances in natural silicate glasses: Application to SR-XRF, LA-ICP-MS and SIMS techniques(2017)
; ; ; ; ; ; ; ; ; ; ; ; ; ;Paonita, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Cadoux, A.; ISTO ;Iacono Marziano, G.; ISTO ;Deloule, E.; CRPG ;Aiuppa, A.; Unipa ;Eby, N.; Massachusset university ;Costa, M.; Unipa ;Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Berlo, K.; McGill University ;Geraki, K.; Harwall Campus ;Mather, T.; University of Oxford ;Pyle, D.; University of Oxford ;Di Carlo, I.; ISTO; ; ; ; ; ; ; ; ; ; ; ; Measuring the low bromine abundances in Earth's materials remains an important challenge in order to constrain the geodynamical cycle of this element. Suitable standard materials are therefore required to establish reliable analytical methods to quantify Br abundances. In this study we characterise 21 Br-doped glasses synthesized from natural volcanic rocks of mafic to silicic compositions, in order to produce a new set of standards for Br analyses using various techniques. The nominal Br contents (amounts of Br loaded in the experimental samples) of 15 of 21 glasses were confirmed within 20% by instrumental neutron activation analysis (INAA). Using this newset of standards, we compare three micro-analytical approaches to measure Br contents in silicate glasses: synchrotron X-ray fluorescence (SR-XRF), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). With SR-XRF, the Br contents of the standard glasses were determined with the highest accuracy (b10% for Br ≥ 10 ppm; N25% for Br ≤ 5 ppm), and high precision (b10% for Br contents N10 ppm; 20–30% for Br ≤ 10 ppm). The detection limit was estimated to be b1 ppm Br. All those factors combined with a high spatial resolution (5 × 5 μm for the presented measurements), means that SR-XRF iswell suited to determine the lowBr abundance in natural volcanic glasses (crystal-hosted melt inclusions or matrix glasses of crystallized samples). At its current stage of development, the LA-ICP-MS method allows the measurement of hundreds to thousands ppm Br in silicate glasses with a precision and accuracy generally within 20%. The Br detection limit of this method has not been estimated but its low spatial resolution (90 μm) currently prevents its use to characterise natural volcanic glasses, however it is fully appropriate to analyse super liquidus or sparsely phyric, Br-rich experimental charges. Our study shows that SIMS appears to be a promising technique to measure the lowBr contents of natural volcanic glasses. Its spatial resolution is relatively good (~15 μm) and, similarly to SR-XRF, the detection limit is estimated to be ≤ 1 ppm. Using our new set of standards, the Br contents of two MPI-DING reference glasses containing ≤ 1.2 ppm of Br were reproduced with precision b5% and accuracy b20%. Moreover, SIMS presents the advantage of being a more accessible instrument than SR-XRF and data processing is more straightforward.283 7 - PublicationRestrictedNoble gas solubilities in silicate melts: New experimental results and a comprehensive model of the effects of liquid composition, temperature and pressure(2010-12-13)
; ; ; ; ; ;Iacono Marziano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Paonita, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Rizzo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Scaillet, B.; ISTO-Orleans ;Gaillard, F.; ISTO-Orleans; ; ; ; New experimental data of Ar and Ne solubility at pressures up to 360 MPa in alkali-basaltic (Mt. Etna, Italy) and rhyolitic (Vulcano Island, Italy) melts are presented. Solubility experiments have been conducted in internally heated pressure vessels at 1200 °C under nominally anhydrous conditions. Ar and Ne contents dissolved in the experimental glasses were then measured by quadrupole mass spectrometry. Over the pressure range investigated, Ar and Ne solubilities vary linearly with Ar and Ne pressures and can be described by Henry's constant (kAr,Ne=PAr, Ne /xAr, Ne, where PAr, Ne is the partial pressure of Ar or Ne and xAr, Ne is the molar fraction of Ar or Ne in the melt) of 7.6±0.8×105 and 1.9±0.4×105 MPa, respectively for Ar and Ne in the basaltic melt and 1.5±0.2×105 and 3.8±0.2×104 MPa, respectively for Ar and Ne in the rhyolitic melt. In accordance with existing models, rhyolitic melts show higher noble gas solubilities than basaltic melts, Ne solubility being higher than that of Ar in a given composition. We propose a semi-empirical model of noble gas (Ar, Ne and He) solubility calibrated on a very large set of measurements in natural and synthetic silicate melts. The model expands the concept of ionic porosity in terms of porosity accessible for noble gas dissolution in melt, taking into account the large-scale structural effects of cations, as well as temperature and pressure. The model is valid over a wide range of temperatures (800–1600 °C), pressures (up to 3 GPa) and compositions, being useful for both geological and physico-chemical studies.126 23 - PublicationOpen AccessMelt inclusions track melt evolution and degassing of Etnean magmas in the last 15 ka(2019)
; ; ; ; ; ; ; ; ; ;; ; ;; ;We present major elements compositions and volatiles contents of olivine-hosted melt inclusions from Etna volcano (Italy), which extend the existing database with the aim of interpreting the chemical variability of Etnean magmas over the last 15 ka. Olivine phenocrysts were selected from the most primitive Fall Stratified (FS) eruptive products of picritic composition (Mg# = 67–70, Fo89–91), the Mt. Spagnolo eccentric lavas (Mg# = 52–64, Fo82–88) and among the more recent 2002–2013 eruptive products (Mg# = 33–53, Fo68–83). Crystal fractionation and degassing processes were modeled at temperatures of 1050–1300 °C, pressures <500 MPa, and oxygen fugacity between 1 and 2 log units above the nickel-nickel oxide buffer, in order to interpret melt inclusions data. Melt inclusions show a great variability in major elements chemistry (e.g., 44–57 wt% SiO2, 3–16 wt% CaO, 4–13 wt% FeO, 2–12 wt% MgO, 1–6 wt% K2O), designating a continuous differentiation trend from FS toward 2013 entrapped melts, which is mostly reproduced by the fractional crystallization of olivine + spinel + clinopyroxene ± plagioclase, in order of appearance. Volatile contents in the glass inclusions are also extremely variable, with maxima up to 6 wt% H2O and 0.6 wt% CO2 in FS melt inclusions, and up to 0.43 wt% S in Mt. Spagnolo inclusions. H2O and CO2 contents in the melt inclusions suggest minimum entrapment depths of 4–19 km (below crater level) for FS inclusions and <10 km for the 2002–2013 trachybasalts. Petrological arguments coupled to the modeling of fractional crystallization and degassing processes concur to suggest that magmas from Mt. Spagnolo and the recent eruptions may be produced by differentiation from the most primitive volatile-rich FS magma along variable P-T paths, occasionally accompanied by secondary processes as crustal assimilation, mixing, and CO2 flushing. We do not exclude the occurrence of source processes at Etna, e.g., variable degrees of mantle melting and/or variable degrees of mantle contamination, already proposed by previous authors. Our data, nevertheless, suggest that the first-order features of the Etnean magmas erupted in the last 15 ka can be modeled by differentiation through fractional crystallization and degassing.740 29 - PublicationOpen AccessSulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing(2020-10-20)
; ; ; ; ; ; ; ; ; ; ; ; ; Sulphur behaviour and variations in redox conditions during magma differentiation and degassing in the Mt Etna (Italy) volcanic system have been explored by integrating the study of olivine-hosted melt inclusions (MIs) with an experimental survey of sulphur solubility in hydrous basaltic magmas. Sulphur solubility experiments were performed at conditions relevant to the Etnean plumbing system (1200 C, 200MPa and oxygen fugacity between NNOþ0 2 and NNOþ1 7, with NNO being the nickel–nickel oxide buffer), and their results confirm the important control of oxygen fugacity (fO2) on S abundance in mafic magmas and on S partitioning between fluid and melt phases (DSfluid/melt). The observed DSfluid/melt value increases from 5164 to 14666 when fO2 decreases from NNOþ1 760 5 to NNOþ0 3. Based on the calculated DSfluid/melt and a careful selection of previously published data, an empirical model is proposed for basaltic magmas to predict the variation of DSfluid/melt values with variations in P (25–300 MPa), T (1030–1200 C) and fO2 (between NNO– 0 8 and NNOþ2 4). Olivine-hosted melt inclusions (Fo89-91) from tephra of the prehistoric (4 ka BP) sub-plinian picritic eruption, named FS (‘Fall Stratified’), have been investigated for their major element compositions, volatile contents and iron speciation (expressed as Fe3þ/PFe ratio). These primitive MIs present S content from 235677 to 34456168 ppm, and oxygen fugacity values, estimated from Fe3þ/PFe ratios, range from NNOþ0 760 2 to NNOþ1 660 2. Iron speciation has also been investigated in more evolved and volatile-poorer Etnean MIs. The only primitive melt inclusion from the Mt Spagnolo eruption (4–15 ka BP) presents a S content of 1515649ppm and an estimated fO2 of NNOþ1 460 1. The more evolved MIs (from 2002–2003, 2006, 2008–2009 and 2013 eruptions) have S content lower than 500 ppm, and their Fe3þ/RFe ratios result in fO2 between NNO– 0 960 1 and NNOþ0 460 1. Redox conditions and S behaviour in Etnean magmas during degassing and fractional crystallization were modelled coupling MELTS code with our empirical DSfluid/melt model. Starting from an FS-type magma composition and upon decrease of T and P, fractional crystallization of olivine, clinopyroxene, spinel and plagioclase causes a significant fO2 decrease. The fO2 reduction, in turn, causes a decrease in sulphur solubility and an increase in DSfluid/melt, promoting S exsolution during magma ascent, which further enhances the reduction of fO2. For the evolved MIs of 2002–2013 eruptions, magma differentiation may therefore have played a crucial role in decreasing redox conditions and favouring efficient S degassing. Differently, during the unusual FS eruption, only limited melt evolution is observed and S exsolution seems to have been triggered by a major pressure decrease accompanied by H2O and CO2 exsolution during fast magmatic ascent.172 9 - PublicationRestrictedLimestone assimilation and the origin of CO2 emissions at the Alban Hills (Central Italy): Constraints from experimental petrology(2007-10-01)
; ; ; ;Iacono Marziano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Gaillard, F.; ISTO, Orleans ;Pichavant, M.; ISTO, Orleans; ; The Alban Hills volcanic region (20 km south of Rome, in the Roman Province) emitted a large volume of potassic magmas (N280 km3) during the Quaternary. Chemical interactions between ascending magmas and the ∼7000–8000-m-thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys. In this paper we characterize the effect of carbonate assimilation on phase relationships at 200 MPa and 1150–1050 °C by experimental petrology. Calcite and dolomite addition promotes the crystallization of Ca-rich pyroxene and Mg-rich olivine respectively, and addition of both carbonates results in the desilication of the melt. Furthermore, carbonate assimilation liberates a large quantity of CO2-rich fluid. A comparison of experimental versus natural mineral, glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different Alban Hills eruptions. A maximum of 15 wt.% assimilation is suggested by some melt inclusion and clinopyroxene compositions; however, most of the natural data indicate assimilation of between 3 and 12 wt.% carbonate. Current high CO2 emissions in this area most likely indicate that such an assimilation process still occurs at depth. We calculate that a magma intruding into the carbonate basement with a rate of ∼1–2·106 m3/year, estimated by geophysical studies, and assimilating 3–12 wt.% of host rocks would release an amount of CO2 matching the current yearly emissions at the Alban Hills. Our results strongly suggest that current CO2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate-hosted reservoir at 5–6 km depth, with important consequences for the present-day volcanic hazard evaluation in this densely populated and historical area.166 18