Chapter

Volcanic Degassing: Process and Impact

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Abstract

Volcanic degassing represents an essential component of the global geochemical cycles that determine the state of the atmosphere and climate. It also exerts a first-order influence on the ways in which volcanoes erupt and is thus vital to understanding how volcanoes work and assessing their hazards. This article reviews the sources of volcanic volatiles, their behavior in ascending magmas and surficial reservoirs (including isotopic fractionation), and the processes by which gases separate from melt and reach the atmosphere. A range of field, laboratory, and remote sensing techniques can be applied to measurements and monitoring of volcanic gas and aerosol compositions (elemental, molecular, and isotopic) and flux. It summarizes their application and the general characteristics of volatile emissions associated with different geodynamic settings and volcanic manifestations. Some methods, including those based on petrological and ice core analysis, can even provide estimates of volatile budgets of eruptions that occurred in the distant past. Having considered the source-to-surface processes related to volcanic degassing, it reviews the impacts of emissions on the atmosphere, climate, and environment, from local to global scales, and the associated human and animal health hazards of volcanogenic pollution.

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... Volcanic emissions discharge through a central conduit/conduits, hot springs, fumaroles, crater lakes or diffuse flank degassing (Oppenheimer et al., 2014), whereas non-volcanic degassing can be related to active tectonic settings and geothermal systems where discharge can occur along faults and fractures (Brune et al., 2017;Buttitta et al., 2020;Tamburello et al., 2018). Thus, the migration of gases from the earth's interior to the atmosphere is controlled by the crustal and structural conditions of the respective geological-tectonic setting. ...
... In addition, great attention has been paid to noble gases like helium (He), argon (Ar), or neon (Ne), since they are present in small quantities in high temperature geothermal systems and due to their inert behaviour, allow the determination of the final origin of gases (Ozima, M. and Podosek, 2002;Sano and Fischer, 2013). Thus, geothermal and volcanic gases present a cocktail of different contributions from the mantle, crustal fluids, rocks, and the atmosphere (Mason et al., 2017;Oppenheimer et al., 2014). solubility of common geothermal gases in water is NH 3 >H 2 S>CO 2 >CH 4 >H 2 >O 2 >N 2 with ammonia dissolving first and nitrogen last (D'Amore and H Nicholson, 1993). ...
... indicative for upper mantle values (Marty and Zimmermann, 1999;Oppenheimer et al., 2014). ...
Thesis
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Major challenges during geothermal exploration and exploitation include the structural-geological characterization of the geothermal system and the application of sustainable monitoring concepts to explain changes in a geothermal reservoir during production and/or reinjection of fluids. In the absence of sufficiently permeable reservoir rocks, faults and fracture networks are preferred drilling targets because they can facilitate the migration of hot and/or cold fluids. In volcanic-geothermal systems considerable amounts of gas emissions can be released at the earth surface, often related to these fluid-releasing structures. In this thesis, I developed and evaluated different methodological approaches and measurement concepts to determine the spatial and temporal variation of several soil gas parameters to understand the structural control on fluid flow. In order to validate their potential as innovative geothermal exploration and monitoring tools, these methodological approaches were applied to three different volcanic-geothermal systems. At each site an individual survey design was developed regarding the site-specific questions. The first study presents results of the combined measurement of CO2 flux, ground temperatures, and the analysis of isotope ratios (δ13CCO2, 3He/4He) across the main production area of the Los Humeros geothermal field, to identify locations with a connection to its supercritical (T > 374◦C and P > 221 bar) geothermal reservoir. The results of the systematic and large-scale (25 x 200 m) CO2 flux scouting survey proved to be a fast and flexible way to identify areas of anomalous degassing. Subsequent sampling with high resolution surveys revealed the actual extent and heterogenous pattern of anomalous degassing areas. They have been related to the internal fault hydraulic architecture and allowed to assess favourable structural settings for fluid flow such as fault intersections. Finally, areas of unknown structurally controlled permeability with a connection to the superhot geothermal reservoir have been determined, which represent promising targets for future geothermal exploration and development. In the second study, I introduce a novel monitoring approach by examining the variation of CO2 flux to monitor changes in the reservoir induced by fluid reinjection. For that reason, an automated, multi-chamber CO2 flux system was deployed across the damage zone of a major normal fault crossing the Los Humeros geothermal field. Based on the results of the CO2 flux scouting survey, a suitable site was selected that had a connection to the geothermal reservoir, as identified by hydrothermal CO2 degassing and hot ground temperatures (> 50 °C). The results revealed a response of gas emissions to changes in reinjection rates within 24 h, proving an active hydraulic communication between the geothermal reservoir and the earth surface. This is a promising monitoring strategy that provides nearly real-time and in-situ data about changes in the reservoir and allows to timely react to unwanted changes (e.g., pressure decline, seismicity). The third study presents results from the Aluto geothermal field in Ethiopia where an area-wide and multi-parameter analysis, consisting of measurements of CO2 flux, 222Rn, and 220Rn activity concentrations and ground temperatures was conducted to detect hidden permeable structures. 222Rn and 220Rn activity concentrations are evaluated as a complementary soil gas parameter to CO2 flux, to investigate their potential to understand tectono-volcanic degassing. The combined measurement of all parameters enabled to develop soil gas fingerprints, a novel visualization approach. Depending on the magnitude of gas emissions and their migration velocities the study area was divided in volcanic (heat), tectonic (structures), and volcano-tectonic dominated areas. Based on these concepts, volcano-tectonic dominated areas, where hot hydrothermal fluids migrate along permeable faults, present the most promising targets for future geothermal exploration and development in this geothermal field. Two of these areas have been identified in the south and south-east which have not yet been targeted for geothermal exploitation. Furthermore, two unknown areas of structural related permeability could be identified by 222Rn and 220Rn activity concentrations. Eventually, the fourth study presents a novel measurement approach to detect structural controlled CO2 degassing, in Ngapouri geothermal area, New Zealand. For the first time, the tunable diode laser (TDL) method was applied in a low-degassing geothermal area, to evaluate its potential as a geothermal exploration method. Although the sampling approach is based on profile measurements, which leads to low spatial resolution, the results showed a link between known/inferred faults and increased CO2 concentrations. Thus, the TDL method proved to be a successful in the determination of structural related permeability, also in areas where no obvious geothermal activity is present. Once an area of anomalous CO2 concentrations has been identified, it can be easily complemented by CO2 flux grid measurements to determine the extent and orientation of the degassing segment. With the results of this work, I was able to demonstrate the applicability of systematic and area-wide soil gas measurements for geothermal exploration and monitoring purposes. In particular, the combination of different soil gases using different measurement networks enables the identification and characterization of fluid-bearing structures and has not yet been used and/or tested as standard practice. The different studies present efficient and cost-effective workflows and demonstrate a hands-on approach to a successful and sustainable exploration and monitoring of geothermal resources. This minimizes the resource risk during geothermal project development. Finally, to advance the understanding of the complex structure and dynamics of geothermal systems, a combination of comprehensive and cutting-edge geological, geochemical, and geophysical exploration methods is essential.
... Les émissions de gaz sont souvent associées à des zones volcaniques actives ou en sommeil et à des régions affectées par la tectonique extensive (par exemple, O'Nions et Oppenheimer et al., 2014). La surveillance des fluides (compositions chimiques et isotopiques et propriétés physiques) dans les régions volcaniques fournit des informations importantes sur les processus intervenant en profondeur (par exemple, Agusto et al., 2013;Barry et al., 2013Barry et al., , 2014Caliro et al., 2015;Christopher et al., 2010;Edmonds, 2008;Fischer, 2008;Mazot et al., 2011;Roulleau et al., 2016;Ruzié et al., 2012;Tassi et al., 2010, Wei et al. ., 2016. ...
... D'autre part, le changement de composition des fluides peut également être corrélé avec la sismicité à l'échelle régionale (par exemple, Bräuer et al., 2008Bräuer et al., , 2018Cardellini et al., 2017;Chiodini et al., 2004;Melián et al., 2012). La compréhension des facteurs de contrôle des émissions de gaz dans les zones volcaniques actives et dormantes a beaucoup progressé au cours des deux dernières décennies (Aiuppa et al., 2007;Edmonds, 2008;Moussallam et al., 2018;Oppenheimer et al., 2014); cependant, beaucoup moins d'attention a été accordée aux zones volcaniques apparemment inactives . Ce sont des volcans dont l'éruption s'est déroulée il y a au moins 10 ka et qui, à la surface, ne montrent aucun signe de réveil. ...
... Ainsi, une source de magma avec une valeur relativement faible en isotope de He (3.10 Ra), similaire à celle proposée pour les systèmes volcaniques du centre de l'Italie, semble être viable sous Ciomadul. Ceci diffère de la valeur de SCLM détectée sur le champ volcanique de Persani (Althaust et al., 1998; cette étude) à proximité ainsi que dans le bassin de Pannonian Cornides, 1993;Palcsu et al., 2014) Oppenheimer et al., 2014). Monitoring of fluids (chemical and isotopic compositions and physical properties) in volcanic regions provides important information concerning the processes occurring at depth (e.g., Agusto et al., 2013;Barry et al., 2013Barry et al., , 2014Caliro et al., 2015;Christopher et al., 2010;Edmonds, 2008;Fischer, 2008;Mazot et al., 2011;Roulleau et al., 2016;Ruzié et al., 2012;Tassi et al., 2010Tassi et al., , 2011Tassi et al., , 2016Wei et al., 2016). ...
Thesis
Dans mon projet, j'ai utilisé les gaz nobles (He, Ne, Ar, Kr et Xe) pour étudier les processus naturels se déroulant dans différents contextes géodynamiques (c.-à-d. subduction, collision continentale, rifting), montrant ainsi comment l'utilisation des gaz rares est fondamentale pour contraindre l'origine des substances volatiles et comment ils permettent une évaluation qualitative et quantitative des processus (interaction eau-gaz-roche) qui se produisent pendant la remontée des fluides de l'intérieur de la Terre vers l'atmosphère. Les résultats de mon projet peuvent être résumés en cinq thèmes principaux : 1) Aperçu de l’histoire du dégazage du manteau terrestre à partir d'analyses de haute précision des gaz rares du gaz magmatique ; 2) Systématique des gaz nobles et des isotopes du carbone sur le volcan Ciomadul, apparemment inactif (Roumanie): Preuve du dégazage volcanique ; 3) Fluides dérivés du manteau dans le bassin sédimentaire de Java oriental, Indonésie ; 4) Dégazage des volatiles du manteau dans un régime tectonique de compression hors du volcanisme: rôle de la délamination continentale ; 5) Dégazage continental de l'hélium dans un contexte tectonique actif (nord de l'Italie) : le rôle de la sismicité.
... Reproducibility of δ 18 O and δD measurements is typically ±0.2‰ and ± 3‰, respectively (1σ). Sisotope ratios were determined (on splits of the same whole-rock samples) at the G.G. Hatch Stable Isotope Laboratory of the Also shown are the fields of hightemperature volcanic gases and "volcanic arc andesitic waters" (box A), deep brines from a geothermal well at Sulphur Springs (box B), deep steam condensates from the geothermal well (box C), and fumarolic steam from Sulphur Springs (X symbols in box C) (comparative data from Bath, 1977;Goff and Vuataz, 1984;Mizutani et al., 1986, Taran et al., 1997, 2002Oppenheimer et al., 2014). ...
... In regard to the third possibility -that of progressive isotopic enrichment in both 18 O and D due to non-equilibrium surface evaporation -the resulting slopes should in theory lie in the 3-5 range, depending on air humidity (cf. Oppenheimer et al., 2014). Many thermal pools in geothermal systems do in fact show slopes between 3 and 5 (e.g., Delmelle et al., 2000;Tassi et al., 2005;González-Partida et al., 2005;Rouwet et al., 2008), although processes other than evaporation, e.g., mixing with magmatic waters, have commonly been invoked. ...
... Such trends may in fact be a common feature of low-latitude regions where meteoric waters have high δD values (−20 to +10‰) and therefore the evaporated end-member will have an even higher value. This raises the possibility that some of the isotopic trends shown by geothermal waters at mid-latitudes are not necessarily the result of mixing between meteoric and andesitic-magmatic waters, as is commonly inferred, but could be the result of evaporative surface processes, a point also made by Oppenheimer et al. (2014). ...
Article
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Sulphur Springs is a vigorous geothermal field associated with the Soufrière Volcanic Centre in southern Saint Lucia. Intensely altered rocks occur over an area of at least 200×400 m, together with bubbling hot pools and fumaroles. The pools are sodium‑calcium-sulphate type, with pHs of 3–7 and temperatures of 41–97 °C. Fumaroles have temperatures up to, and at times above 100 °C. Gases collected from both fumaroles and bubbling pools have high contents of CO2 (601–993 mmol/mol) and commonly high H2S (3–190 mmol/mol). Least-altered host rocks surrounding Sulphur Springs comprise calc-alkaline, feldspar-quartz-porphyritic dacites of near-uniform chemical composition. These rocks, which form massive domes and volcaniclastic units, were emplaced 13–30 ka ago (Lindsay et al., 2013). Within the geothermal field, the dacites have been moderately to highly altered to acid-sulphate assemblages of kaolinite, illite, smectite, alunite, natroalunite, cristobalite, opaline silica, native sulphur, jarosite and amorphous compounds. Muddy sediments from grey to blackish thermal pools additionally contain iron sulphides. Despite intense alteration of the volcanic rocks (and derived volcaniclastic sediments), Zr and Ti have remained essentially immobile, which allows identification of the precursors (dacites) and calculation of mass changes. Many of the altered rocks and sediments show major depletions of Fe, Mg, Ca, Na. Extremely altered samples additionally show notable losses of Al, P, K, REE and Y, implying leaching by highly acidic waters. A few of the highly altered rocks, however, have gained Al, together with P, presumably due to neutralization or evaporation of acidic thermal waters. Also present within the geothermal field are metre-scale zones with very high contents of silica and native sulphur, and <1% Al2O3. Based on mass change results, the silica in the silica-sulphur zones, although recrystallized, was mainly inherited from the precursor dacites, rather than added as new hydrothermal precipitates. Surface thermal waters define a linear trend in a plot of δ18O vs. δD, and reach high levels of isotopic enrichment. The enrichment trend is ascribed to progressive evaporation in the thermal pools. The low slope of the isotopic trend (1.4) is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 °C from the deep brine that underlies the geothermal field. The whole-rock O-H-isotopic composition of four highly altered samples (kaolinite-smectite-opal-sulphates) can be accounted for if the alteration fluid was a 50:50 mixture of steam and meteoric water, and alteration occurred at 50–125 °C. Whole-rock δ34S values of samples containing variable amounts of sulphates, sulphides and native S are all notably negative (−5 to −16‰), consistent with derivation of sulphur from volcanic gases such as SO2 and H2S. Altered rocks and thermal pool sediments in the geothermal field are commonly enriched in Hg and Se (up to 50 mg/kg). At Sulphur Springs, primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters. In many cases, this has led to substantial mass losses or gains in Al, P and REEs. Regardless of the degree of alteration, however, the precursor rocks can still be identified using Ti-Zr relations.
... It is therefore necessary to distinguish between hazards on a global scale, which are likely to modify climatic and environmental conditions and disrupt ecosystems in the long term, and hazards on a local scale, which have more limited and often shorter-lived effects, but which are potentially dramatic for the populations exposed. Wallace (2005) and Oppenheimer et al. (2014)) and related volcanic gas composition (from Symonds et al. (1994) and Oppenheimer et al. (2014)). The abbreviation <d.l. ...
... It is therefore necessary to distinguish between hazards on a global scale, which are likely to modify climatic and environmental conditions and disrupt ecosystems in the long term, and hazards on a local scale, which have more limited and often shorter-lived effects, but which are potentially dramatic for the populations exposed. Wallace (2005) and Oppenheimer et al. (2014)) and related volcanic gas composition (from Symonds et al. (1994) and Oppenheimer et al. (2014)). The abbreviation <d.l. ...
Chapter
The complexity of understanding volcanic risk is partly due to the fact that it is the result of different hazards, some of which are directly linked to the eruptive activity, such as, gas, lava flows, pyroclastic flows and ash fallout, and others which are directly or indirectly induced by these hazards, such as, debris avalanches, tsunamis, mudflows or lahars. A wide range of seismic phenomena is associated with volcanic activity. The main sources of seismic signals are: magma transfers; hydrothermal activity; and volcano‐tectonic phenomena. Understanding the hazard associated with volcanic gases means first of all understanding the physico‐chemistry of the outgassing process. Volcanic explosions produce and eject tephra of various sizes and gases. Tephra are classified into three main classes: bombs, lapilli and ash. Lahars are part of a continuum of water‐rich flows, but sediment concentration, particle size distribution and density help distinguish the following two categories: hyperconcentrated flows and debris flows.
... Volcanic gases are emitted to the atmosphere both as diffuse degassing (Chiodini et al., 1996;Hernández et al., 2001;Pérez et al., 2011;Melián et al., 2014Melián et al., , 2019Cardellini et al., 2017;Padrón et al., 2021) and visible emanations (e.g., fumaroles, plumes; Giggenbach, 1975;Fisher et al., 1996;Hilton et al., 2002;Melián et al., 2012;Gresse et al., 2018). The composition of the fluids discharged by volcanoes are a reflection of 1) deep processes such as the injection of new magma, degassing of deep mafic magma in the lower crust etc. and 2) secondary processes, as for example gas re-equilibrium, interaction with meteoric water-fed, water-rock interaction etc. (Giggenbach, 1980(Giggenbach, , 1984(Giggenbach, , 1987(Giggenbach, , 1993Chiodini and Marini 1998;Taran and Giggenbach, 2003;Oppenheimer et al., 2012). Increases of the volatile content in magma plays a fundamental role in pre-eruptive pressurization of volcanic systems (Wallace, 2001). ...
... H 2 is a well-known geochemical tracer in volcanic systems. H 2 plays a role in key redox reactions that occur in magmatic gases, because of its relationship to fO 2 via the water dissociation reaction (e.g., Giggenbach 1987;Oppenheimer et al., 2012). Time series of He/ CO 2 and H 2 /CO 2 for the Pico do Fogo fumaroles are given in Figures 10B,C. ...
Article
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We report the results of the geochemical monitoring of the fumarolic discharges at the Pico do Fogo volcano in Cape Verde from 2007 to 2016. During this period Pico do Fogo experienced a volcanic eruption (November 23, 2014) that lasted 77 days, from a new vent ∼2.5 km from the fumaroles. Two fumaroles were sampled, a low (F1∼100°C) and a medium (F2∼300°C) temperature. The variations observed in the δ18O and δ2H in F1 and F2 suggest different fluid source contributions and/or fractionation processes. Although no significant changes were observed in the outlet fumarole temperatures, two clear increases were observed in the vapor fraction of fumarolic discharges during the periods November 2008–2010 and 2013–2014. Also, two sharp peaks were observed in CO2/CH4 ratios at both fumaroles, in November 2008 and November 2013. This confirms that gases with a strong magmatic component rose towards the surface within the Pico do Fogo system during 2008 and 2013. Further, F2 showed two CO2/Stotal peaks, the first in late 2010 and the second after eruption onset, suggesting the occurrence of magmatic pulses into the volcanic system. Time series of He/CO2, H2/CO2 and CO/CO2 ratios are low in 2008–2009, and high in 2013–2014 period, supporting the hypothesis of fluid input from a deeper magmatic source. Regarding to the isotopic composition, increases in air-corrected 3He/4He ratios are observed in both fumaroles; F1 showed a peak in 2010 from a minimum in 2009 during the first magmatic reactivation onset and another in late 2013, while F2 displayed a slower rise to its maximum in late 2013. The suite of geochemical species analyzed have considerably different reactivities, hence these integrated geochemical time-series can be used to detect the timing of magmatic arrivals to the base of the system, and importantly, indicate the typical time lags between gas release periods at depth and their arrival at the surface. The high 3He/4He ratios in both fumaroles in the range observed for mid-ocean ridge basalts, indicating that He is predominantly of upper mantle origin. This work supports that monitoring of the chemical and isotopic composition of the fumaroles of the Pico do Fogo volcano is a very important tool to understand the processes that take place in the magmatic-hydrothermal system and to be able to predict future episodes of volcanic unrest and to mitigate volcanic risk.
... Because of spatial/temporal variability, and due to the fact that some arc volcanoes remain unsampled to date, mostly due to their remoteness and inaccessibility, arc-scale noble gas compositional catalogues (Hilton et al., 2002;Sano and Fischer, 2013) remain biased by the incomplete and heterogeneous data set available. Nonetheless, global reviews [Hilton et al., 2002;Sano and Fischer, 2013;Oppenheimer et al., 2014;Mason et al., 2017] provide convincing evidence for arc-scale correlations between isotope tracers and slab/crustal processes. ...
... 2002; Sano and Fischer, 2013;Oppenheimer et al., 2014;Mason et al., 2017) reported 3 He/ 4 He averages of 3.2 ± 1.0 R A and 5.7 ± 2.4 R A (<< MORB-range of 8 ± 1 R A ) for Ecuador and Colombia, respectively (e.g., Hilton et al., 2002). These may in large reflect significant extents of mixing between mantle-derived and radiogenic helium produced in the crust. ...
Article
Trace volatile elements like He are key for understanding the mantle source signature of magmas and to better constrain the relative roles of subduction and crustal processes to the variability of along-arc chemical and isotopic signatures of magmatic fluids. Here we report on noble gas abundances and isotopic data of Fluid Inclusions (FIs) in eruptive products and/or fumarolic gases from the Colombia-Ecuador segment of Andean Northern Volcanic Zone (NVZ). FIs in olivine phenocrysts from Ecuador (El Reventador, Cotopaxi and Tungurahua) yield air-normalized corrected ³He/⁴He ratios of 7.0–7.4 RA, within the MORB range (8 ± 1 RA). With exception of the Cotopaxi lavas (opx < <oliv.), these are indistinguishable of those obtained for their cogenetic orthopyroxene pairs and of gas emissions previously reported in literature. Olivine phenocrysts from Nevado del Ruiz fissure lavas also yield the highest ³He/⁴He (8.5 ± 0.3 RA) for this volcanic system, which is in the range of fumarolic gases for Galeras (previously reported as high as 8.8 RA and here measured to a maximum of 8.3 ± 0.1 RA). Our dataset highlights disparities between isotope signatures of eruptive products from Ecuador (avg. ~7.2 RA) and those reported for the Colombian portion of the NVZ (avg. ~8.5 RA). Previous studies on the geochemistry of erupted products put in evidence significant along-arc variations ascribed either to the involvement of different slab components, or to variable depths of evolution of arc magmas within the continental crust. However, the same variation is not discernible in the signature of noble gases, especially helium, from FIs and gas emissions analyzed in this study, with little inter-variation between Cotopaxi, Reventador and Tungurahua (all within 0.2 RA from the Ecuador average of 7.2) and Galeras and Nevado del Ruiz, whose maximum values differ by ~0.3 RA. We therefore suggest a homogenous MORB-like ³He/⁴He signature for the mantle wedge beneath this arc segment, whereby along-arc variations in crustal thickness (from <35 km at the northernmost part of the segment to ≥50 km at the Ecuadorian arc segment) may factor largely into the variability recorded on our data set. The first CO2/³He ratios obtained in FIs from Andean rocks support the hypothesis of increasing crustal contamination from Colombia to Ecuador, concomitant with increasing crustal thicknesses under the respective arc regions.
... Gases and other materials emitted from volcanic systems are originally sourced in variable proportions from mantle-generated magmas, crustal rocks and fluids, and the mantle wedge and subducting slab in the case of volcanic arc systems (Oppenheimer et al., 2014). Their release to the Earth's surface occurs through a number of physical features including gas vents (fumaroles) and lava lakes within summit craters, subsidiary fumaroles and diffuse degassing zones on volcano flanks, as well as hot springs, volcanic lakes, mud pots, and fumaroles rooted in volcano-hosted hydrothermal aquifers ( Fig. 1; Fischer and Chiodini, 2015;Gresse et al., 2018). ...
... sulfide (H 2 S), and hydrogen halides such as HF and HCl (Delmelle, 2003;Oppenheimer et al., 2014). They also contain a range of metals such As, Hg, Pb, Sb, Se, and Tl (Buat-Menard and Arnold, 1978;Bernard and Le Guern, 1986;Mather et al., 2012;Moune et al., 2010). ...
Article
Volcanism is a potentially important natural source of mercury (Hg) to the environment. However, its impact on the global Hg cycle remains poorly understood despite advances over the last five decades. This represents a major uncertainty in our understanding of the relative contributions of natural and anthropogenic Hg sources to the global atmosphere. This uncertainty, in turn, impacts evaluation of the effectiveness of policies to mitigate the impact of anthropogenic Hg on the environment. Here we critically review recent progress in volcanic Hg emission research, including advances in sampling methods and understanding of the post-emission behavior of Hg in the atmosphere. Our statistical analysis of the limited available data shows that the plumes of non-arc volcanoes exhibit significantly higher Hg concentrations than arc volcanoes, yet the latter emit 3-fold higher Hg fluxes on average. Arc volcanism also dominates volcanic gas emissions globally, indicating that arc volcanoes should be a priority for future Hg emission research. We explore several methodological challenges that continue to hinder progress in quantifying global volcanic Hg emissions, and discuss the importance of longer time-frame data collection to capture temporal variations in emissions. Recommendations are proposed for working toward a more accurate assessment of the global volcanic Hg flux. A detailed summary of all published volcanic Hg emissions data worldwide is also presented as a reference tool for future work.
... [3], [4], [5], [6], and references therein). 25 The gas composition of the emission plumes can, inter alia, be studied using ground-based passive remote sensing techniques. ...
... Table A1. Pyplis example scripts, sub-categorised into introductory scripts (0.1-0.7) and scripts related to the emission-rate analysis of the Etna test data (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) In order to use all features of Pyplis (e.g. automatic file separation, automatic dark and offset 510 correction, geometrical calculations), certain camera characteristics need to be provided by the user. ...
Preprint
UV SO2 cameras have become a common tool to measure and monitor SO2-emission-rates, mostly from volcanoes but also from anthropogenic sources (e.g. power plants or ships). In the past years, the analysis of UV SO2 camera data has seen many improvements. As a result, for many of the required analysis steps, several alternatives exist today. This inspired the development of Pyplis, an open-source software toolbox written in Python 2.7, which aims to unify the most prevalent methods from literature within a single, cross-platform analysis framework. Pyplis comprises a vast collection of algorithms relevant for the analysis of UV SO2 camera data. These include several routines to retrieve plume background radiances as well as routines for cell and DOAS based camera calibration. The latter includes two independent methods to identify the DOAS field-of-view within the camera images. Plume velocities can be retrieved using an optical flow algorithm as well as signal cross-correlation. Furthermore, Pyplis includes a routine to perform a first order correction of the signal dilution effect. All required geometrical calculations are performed within a 3D model environment allowing for distance retrievals to plume and local terrain features on a pixel basis. SO2-emission-rates can be retrieved simultaneously for an arbitrary number of plume intersections. Pyplis has been extensively and successfully tested using data from several field campaigns. Here, the main features are introduced using a dataset obtained at Mt. Etna, Italy on 16 September 2015.
... Volcanic plumes, fumaroles, and degassing grounds release incessantly magmatic volatiles (e.g., H 2 O, SO 2 , and CO 2 ) [7], representing the external appearance of deep magma degassing [8,9]. These volatiles are a source of priceless data for forecasting the likelihood of a volcanic eruption. ...
... 2020, 10, 6402 3 of 23 they can perform measurements from a safe area, while also allowing (semi)-continuous operation during eruptions. Moreover, gas amounts can be retrieved non-invasively in near real-time, obviating the need for successive laboratory analysis, thus avoiding possible sample contamination, and-unlike in situ sampling-standoff sensing techniques measure integrated or range-resolved gas concentrations through cross-sections of the plume, thus providing a more informative characterization of composition and flux of the volcanic plume [8]. ...
Article
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Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. Abstract: Volcanologists have demonstrated that carbon dioxide (CO 2) fluxes are precursors of volcanic eruptions. Controlling volcanic gases and, in particular, the CO 2 flux, is technically challenging, but we can retrieve useful information from magmatic/geological process studies for the mitigation of volcanic hazards including air traffic security. Existing techniques used to probe volcanic gas fluxes have severe limitations such as the requirement of near-vent in situ measurements, which is unsafe for operators and deleterious for equipment. In order to overcome these limitations, a novel range-resolved DIAL-Lidar (Differential Absorption Light Detection and Ranging) has been developed as part of the ERC (European Research Council) Project "BRIDGE", for sensitive, remote, and safe real-time CO 2 observations. Here, we report on data collection, processing techniques, and the most significant findings of the experimental campaigns carried out at the most hazardous volcanic areas in Italy: Pozzuoli Solfatara (Phlegraen Fields), Stromboli, and Mt. Etna. The BrIdge voLcanic LIdar-BILLI has successfully obtained accurate measurements of in-plume CO 2 concentration and flux. In addition, wind velocity has also been retrieved. It has been shown that the measurements of CO 2 concentration performed by BILLI are comparable to those carried out by volcanologists with other standard techniques, heralding a new era in the observation of long-term volcanic gases.
... The accurate retrieval of the source location and mass loading of volcanic plumes is essential to study volcanic processes and mitigate the associated hazards. In particular, Sulfur Dioxide (SO 2 ) gas emissions are a key parameter informing on the eruptive activity of volcanoes (Oppenheimer et al., 2014). An increase in SO 2 flux is for instance often considered as a precursor to volcanic eruptions. ...
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Volcanic sulfur dioxide (SO2) satellite observations are key for monitoring volcanic activity, and for mitigation of the associated risks on both human health and aviation safety. Automatic analysis of this data source, including robust source emission retrieval, is in turn essential for near real-time monitoring applications. We have developed fast and accurate SO2 plume classifier and segmentation algorithms using classic clustering, segmentation and image processing techniques. These algorithms, applied to measurements from the TROPOMI instrument onboard the Sentinel-5 Precursor platform, can help in the accurate source estimation of volcanic SO2 plumes originating from various volcanoes. In this paper, we demonstrate the ability of different pixel classification methodologies to retrieve SO2 source emission with a good accuracy. We compare the algorithms, their strengths and shortcomings, and present plume classification results for various active volcanoes throughout the year 2021, including examples from Etna (Italy), Sangay and Reventador (Ecuador), Sabancaya and Ubinas (Peru), Scheveluch and Klyuchevskoy (Russia), as well as Ibu and Dukono (Indonesia). The developed algorithms, shared as open-source code, contribute to improving analysis and monitoring of volcanic emissions from space.
... Les éruptions volcaniques sont une source majeure d'éléments traces (e.g., As, Cd, Cu, Pb, and Se) (Nriagu, 1989 ;Oppenheimer et al., 2003). En effet les particules et les gaz injectés dans l'atmosphère peuvent être une source naturelle d'éléments traces dans la troposphère, la stratosphère et la surface terrestre (Nho et al., 1996 ;Dams et al., 1973 (Symonds and Reed, 1993;Zreda-Gostynska et al., 1997). ...
... One recurrent sign of dormant volcanoes becoming restless is an escalation in surface degassing activity 13,14 , typically manifesting as accelerating outgassing rates 2,15 , increasing fumarole temperatures and/or extension of degassing areas 16,17 , and increasingly magmatic (and less hydrothermal) chemical characteristics of the emitted gases [18][19][20][21][22][23] . As not all degassing unrests ultimately culminate into eruption 8 , the fundamental challenge is to distinguish, from data streamed by monitoring networks, between pre-eruption magmatic unrests (those driven by magma ascent, and that will culminate into an eruption 24,25 ), failed/ aborted magmatic unrests (in which degassing magma is involved that will not ultimately erupt 26 ), and hydrothermal unrests (in which no magma is involved but hydrothermal/phreatic explosions are still possible 27 ). ...
Article
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The benign fuming activity of dormant volcanoes is punctuated by phases of escalating degassing activity that, on some occasions, ultimately prelude to eruption. However, understanding the drivers of such unrest is complicated by complex interplay between magmatic and hydrothermal processes. Some of the most comprehensively characterised degassing unrest have recently been observed at La Fossa cone on Vulcano Island, but whether or not these episodes involve new, volatile-rich ascending magma remains debated. Here, we use volcanic gas measurements, in combination with melt inclusion information, to propose that heightened sulphur dioxide flux during the intense fall 2021 La Fossa unrest is sourced by degassing of volatile-rich mafic magma. Calculations using a numerical model indicate observations are consistent with the unrest being triggered by the emplacement of ∼3·10⁶ m³ of mafic magma at ∼4–5 km depth. Degassing of mafic magma is argued as a recurrent driver of unrest at dormant volcanoes worldwide.
... Magmatic gases are the drivers for explosive volcanic eruptions, making their sensing and quantification of prime importance for characterizing volcano behavior (Oppenheimer et al., 2014;Vergniolle and Métrich, 2022). The advent of the SO 2 camera technique (see reviews in Kern et al., 2010a, Burton et al., 2015McGonigle et al., 2017) has paved the way to monitoring SO 2 flux emissions at Stromboli (and elsewhere) with finer temporal and spatial resolution (Tamburello et al., 2012;Delle Donne et al., 2017;Aiuppa et al., 2021) than before (Allard et al., 2008). ...
Article
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Improving volcanic gas monitoring techniques is central to better understanding open-vent, persistently degassing volcanoes. SO2 cameras are increasingly used in volcanic gas studies, but observations are commonly limited to one single camera alone viewing the volcanic plume from a specific viewing direction. Here, we report on high frequency (0.5 Hz) systematic measurements of the SO2 flux at Stromboli, covering a 1-year long observation period (June 2017-June 2018), obtained from two permanent SO2 cameras using the same automated algorithm, but imaging the plume from two different viewing directions. Our aim is to experimentally validate the robustness of automatic SO2 camera for volcano monitoring and to demonstrate the advantage of using two co-exposed SO2 camera stations to better capturing degassing dynamics at open-vent volcanoes. The SO2 flux time-series derived from the two SO2 camera stations exhibit good match, demonstrating the robustness of the automatic SO2 camera method. Our high-temporal resolution SO2 records resolve individual Strombolian explosions as transient, repetitive gas bursts produced by the sudden release of over pressurized gas pockets and scoriae. Calculations show that explosive degassing activity accounts for ∼10% of the total SO2 emission budget (dominated by passive degassing) during mild regular open-vent activity. We show that the temporal variations of the explosive SO2 flux go in tandem with changes in total SO2 flux and VLP seismicity, implicating some commonality in the source processes controlling passive degassing and explosive activity. We exploited the spatial resolution of SO2 camera to discriminate degassing at two distinct regions of the crater area, and to minimize biases due by the station position respect to the target plume. We find that the SO2 fluxes from southwest-central (SWCC) and northeast (NEC) crater areas oscillate coherently but those from the NEC are more sensitive to the changes in the volcanic intensity. We interpret this as due to preferential gas/magma channeling into the structurally weaker north-eastern portion of the crater terrace in response to increasing supply rate of buoyant, bubble-rich magma in the shallow plumbing system.
... The composition of the acidic-rain reactant was derived from dissolution of one mole of Erte Ale volcanic gas (Oppenheimer et al., 2014), with an added 1% O 2 (Lu et al., 2014) in 1 kg of water, then equilibrated with a CO 2 partial pressure of 0.05 MPa, as described in Schieber et al. (2017) and tabulated in Appendix S14. An atmospheric CO 2 buffer for both weathering and diagenetic settings limits the model's application to shallow diagenesis and avoids the need to turn off the buffer at an arbitrarily chosen reaction point. ...
Article
Mudstone‐dominated lacustrine strata in the Pahrump Hills area of Gale Crater, Mars, have the most extensive data set of physical and geochemical observations yet collected. Although sparse by Earth standards, a source‐to‐sink portrayal of the sedimentary system that differs substantially from previous work has been extracted by integrating sedimentology, stratigraphy, mineral and elemental analyses, geochemical modelling, laboratory experiments and Earth analogues in a sequence‐stratigraphic and palaeogeographic framework. Approximately 3.5 Ga, these 15 m thick strata contain five facies that range from fine to coarse detrital mudstone with abundant sediment‐incorporative evaporite pseudomorphs. The section is dominated by first‐cycle grains of minimally weathered primary igneous minerals but with four distinct compositions. Bedding in the mudstones comprises planar‐parallel beds, current ripples and wave‐induced structures, with common and widespread truncation. The absence of primary desiccation and synaeresis cracks is probably due to minimal clay‐mineral content, as supported by lab experiments. Evaporite minerals formed on and within detrital muds shortly after accumulation by evapoconcentration and cooling. The succession contains 16 parasequences in five depositional sequences with all the sequence‐stratigraphic elements known from terrestrial strata. Two of the sequence boundaries are unconformities that record significant shifts in the behaviour and palaeogeographic configuration of the fluvio‐lacustrine system. This contrasts with the previous view that all facies are genetically related. Most of the variability in rock composition can be attributed to stratigraphic changes in provenance that integrate changing drainage basin configurations, type of exposed bedrock and changes in weathering regime. These strata are interpreted as evaporative lake deposits that accumulated in an underfilled lake basin with closed surface hydrography but through‐flowing groundwater. Lake waters were saline to hypersaline, and lake levels, shorelines and salinities fluctuated greatly at various temporal scales.
... In subduction-related settings, the 3 He/ 4 He ratio of the mantle wedge, and thus of magmatic/volcanic gases, is normally expected within the MORB range (8 ± 1 Ra) [87], due to the fact that the oceanic crust originally has a MORB-like signature and early models of noble gases hypothesised a subduction barrier for their recycling into the mantle [101]. However, this is not always observed in arc volcanoes on Earth, where 3 He/ 4 He values lower than 7.0 Ra are often found [70,[102][103][104]. Nevertheless, it must be noted that it is only at volcanic arcs, where continental crust is involved in the subduction, that slab fluids are likely to significantly play a game in determining 3 He/ 4 He values of <<7.0 Ra (e.g., Italy, [47,105]). ...
Article
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Constraining the magmatic 3He/4He signature of fluids degassed from a magmatic system is crucial for making inferences on its mantle source. This is especially important in arc volcanism, where variations in the composition of the wedge potentially induced by slab sediment fluids must be distinguished from the effects of magma differentiation, degassing, and crustal contamination. The study of fluid inclusions (FIs) trapped in minerals of volcanic rocks is becoming an increasingly used methodology in geochemical studies that integrates the classical study of volcanic and geothermal fluids. Here, we report on the first noble gas (He, Ne, Ar) concentrations and isotopic ratios of FI in olivine (Ol) and pyroxene (Px) crystals separated from eruptive products of the Telica and Baru volcanoes, belonging to the Nicaraguan and Panamanian arc-segments of Central America Volcanic arc (CAVA). FIs from Telica yield air corrected 3He/4He (Rc/Ra) of 7.2–7.4 Ra in Ol and 6.1–7.3 in Px, while those from Baru give 7.1–8.0 Ra in Ol and 4.2–5.8 Ra in Px. After a data quality check and a comparison with previous 3He/4He measurements carried out on the same volcanoes and along CAVA, we constrained a magmatic Rc/Ra signature of 7.5 Ra for Telica and of 8.0 Ra for Baru, both within the MORB range (8 � 1 Ra). These 3He/4He differences also reflect variations in the respective arc-segments, which cannot be explained by radiogenic 4He addition due to variable crust thickness, as the mantle beneath Nicaragua and Panama is at about 35 and 30 km, respectively. We instead highlight that the lowest 3He/4He signature observed in the Nicaraguan arc segment reflects a contamination of the underlying wedge by slab sediment fluids. Rc/Ra values up to 9.0 Ra are found at Pacaya volcano in Guatemala, where the crust is 45 km thick, while a 3He/4He signature of about 8.0 Ra was measured at Turrialba volcano in Costa Rica, which is similar to that of Baru, and reflects possible influence of slab melting, triggered by a change in subduction conditions and the contemporary subduction of the Galapagos hot-spot track below southern Costa Rica and western Panama.
... However, the constituents may be also affected by differential fluid delivery from the sea-floor vents (Grenne and Slack, 2005;German and Von Damm, 2006;Fig. 12), and by eruptive gaseous emissions (Oppenheimer, 2014;Yudovich and Ketris, 2015). Several geochemical proxies, such as moderate iron and manganese values (Fe 2 O 3 < 5.3%, MnO 2 < 0.4%; Fig. 10; Table 2), relatively high values of the Al/(Al + Fe + Mn) ratio (>0.6; ...
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A tephra-rich cherty-clayey Famennian succession within the major Brzeźnica olistostrome in the Bardo Mountains, Central Sudetes, SW Poland, preserves a record of the lost ocean later incorporated into the Variscan orogenic belt. Fluctuating but mostly oligotrophic regimes and low primary production levels were influenced by weak upwelling below the perennial oxygen minimum zone, which controlled the interplay between biosiliceous and siliciclastic deposition in the oceanic basin, with episodic oxygen deficiency. The Hangenberg Black Shale has been identified in this oceanic setting based on its characteristics described worldwide (including mercury enrichments). A tectonic uplift of the sediment source area near the Devonian-Carboniferous boundary, recorded in the distinguishing provenance signal of old continental crust, was paired with a global transgression, anoxia, and volcanic episode in an interglacial interval. Assuming paleogeographic affinity with the Bavarian facies of the Saxothuringian terrane, we interpret the allochthonous sediments as part of an accretionary prism that was gravitationally redeposited into the late orogenic basin in front of advancing Variscan nappes. The oceanic basin parental to the Bardo pelagic succession is therefore thought to represent a tract of the waning Saxothuringian Ocean in the Peri-Gondwanan paleogeographic domain that was eventually subducted beneath the Brunovistulian margin of Laurussia. The sediments of the Bardo Ocean basin also include a distal record of Famennian explosive volcanic activity that was likely related to a continental magmatic arc whose remnants are preserved as the Vrbno Group of the East Sudetes.
... Además, la composición varía entre volcanes que tienen diferente origen y por lo tanto diferente tipo de magma. Un panorama más complicado se presenta si las emisiones volcánicas provienen de fumarolas, es decir, fracturas asociadas al edificio volcánico, donde podrían interactuar con aguas subterráneas o marinas, y así modificar la composición química y la concentración de los gases [7]. El H2O(g), independientemente del origen, composición y concentración de los gases, contribuye entre el 50 y 90% del volumen total (% vol.) y es considerado el compuesto gaseoso más abundante en la Figura 2: Simple descripción de la estructura interna (conducto y cámara magmática) y externa (pluma volcánica) de un volcán. ...
Article
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El estudio de los gases volcánicos abarca diferentes procesos que van desde escalas regionales a globales, y que acontecen en una larga escala de tiempo. Las emisiones de gases volcánicos contribuyeron a la creación de la primera atmósfera primordial y actualmente contribuyen a la regulación de los procesos superficiales, como el clima, los procesos biogeoquímicos y la química de aguas superficiales. En la historia de la Tierra, grandes emisiones de gases perturbaron el equilibrio climático y fueron responsables de extinciones masivas. Erupciones catastróficas también emitieron grandes cantidades de gases reactivos, perturbando la química atmosférica generando efectos climáticos importantes e inmediatos. El monitoreo de las emisiones volcánicas constituye un campo muy activo en la investigación de los gases y su interacción con la atmósfera.
... Understanding magmatic volatiles behaviour in terms of the maximum amount that can be dissolved in a silicate melt under a given set of conditions (pressure, temperature, melt composition, and redox state) is crucial for improving the knowledge of magmatic processes and degassing mechanisms involved in volcanic eruptions [Moore, 2008, Oppenheimer et al., 2014. ...
Article
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We present new H2O and CO2 solubility data in mafic to intermediate alkaline magmas from Fasnia and Garachico volcanoes, Tenerife. H2O- and CO2-saturated experiments were conducted at 50–400 MPa, 1200 °C, and O2 from 2 log units below the NiNiO solid buffer to 3.2 log units above it. Although existing solubility models for alkali-rich mafic magmas broadly describe H2O and CO2 behaviour, associated errors are worthy of consideration since they usually exceed 15–20%. For this reason, we have determined the specific solubility laws of basanitic and phonotephritic melts from the Canary Islands. Results show similar H2O solubilities for both compositions, whereas the basanite can dissolve an average of 45% more CO2 than the phonotephrite. By combining these data, we have established a simple empirical model that allows us to calculate melt inclusion entrapment pressures accurately and, therefore, better understand the inner workings of volcanic oceanic islands. Application to El Hierro 2011–2012 and young (20 ka) basanites from this location shows that previous barometric estimates were, on average, overestimated by 15–28%. Our results suggest that magmas rising from depth experienced a first but short episode of equilibration at 8–10 km, whereas the bulk of the crystallization occurred during the subsequent dyke injection, ascent, and degassing at (6–1.5 km).
... Such efforts can be coupled with high-resolution analysis of deep low-frequency earthquakes (DLFEs) 17,18,68,69 to unravel deep magma transport. Improved knowledge of external loading/unloading conditions 67 , continuous monitoring of degassing rate 70 , and the permeability/ rheology of shallow conduit 32,67 can facilitate diagnosing shortterm eruption potential. ...
Article
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Magma ascent, storage, and discharge in the trans-crustal magmatic system are keys to long-term volcanic output and short-term eruption dynamics. How a distinct magma batch transports from a deep reservoir(s) to a pre-eruptive storage pool with eruptible magma remains elusive. Here we show that repetitive very-long-period signals (VLPs) beneath the Aso volcano are preceded by a short-lived (~50-100 s), synchronous deformation event 3 km apart from the VLP source. Source mechanism of a major volumetric component (~50-440 m 3 per event) and a minor low-angle normal-fault component, together with petrological evidence, suggests episodic transport of discrete magma batches from an over-pressured chamber roof to a pre-eruptive storage pool near the brittle-ductile transition regime. Magma ascent velocity, decompression rate, and cumulative magma output deduced from recurrent deformation events before recent 2014 and 2016 eruptions reconcile retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real-time evaluation of upcoming eruptions.
... Sulfur can also be introduced by metamorphic fluids from wall rocks [63,64] or from the deep crust during amphibolite-grade and granulite-grade metamorphism [65]. The δ 34 S values from the Anatahan eruptions showed a range between −0.5‰ and + 2.5‰ [66]. These authors also indicated δ 34 S values from the melts varying from 0 ‰ to + 2‰; however, the δ 34 S values from the sulfates contained in the ash range between + 2.5‰ and + 3‰. ...
Article
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Major trace element analyses, including pyrite chemistry of pyritic mudstones of shallow-marine Singa Formation of Pennsylvanian–Early Permian age have been carried out to assess gold potential, the source of sulfur and organic matter. Regionally, Singa Formation spatially correlates with the Bohorok Formation (Sumatra, Indonesia), the Kaeng Krachang group (Thailand), and the Lebyin group (Burma or Myanmar). In Southeast Asia, this formation is important because it has a record of glacial processes that occurred along the northern margin of Gondwana in the Late Paleozoic age. This study has revealed that mudstones of the Singa Formation, which contain lonestones of glacial origin, deposited under suboxic–oxic conditions in shallow marine environment during Pennsylvanian–Early Permian time. The black mudstones contain total organic carbon which ranges from 0.1 to 0.7 wt.%, and gold content varying from 40 to 62 ppb, making them gold source rocks. This study has revealed diagenetic gold presence in the early pyrite generations (pyrites 1, 2, and 3) in these mudstones with gold content ranging up to 1.6 ppm Au which is indicative of early enrichment of gold. Conversely, late generations of pyrite (pyrites 4, 5, and 6) in these mudstones record low gold content up to 0.5 ppm Au. The δ34S values for pyrite grains range from −24.6‰ to + 6.2‰ likely indicate a combination of magmatic and biogenic source of sulfur. Organic carbon isotope composition of the pebbly mudstone samples shows a wide range from −23.9‰ to −5.8‰ indicating a mixed terrestrial and marine source.
... Such efforts can be coupled with high-resolution analysis of deep low-frequency earthquakes (DLFEs) 17,18,68,69 to unravel deep magma transport. Improved knowledge of external loading/unloading conditions 67 , continuous monitoring of degassing rate 70 , and the permeability/ rheology of shallow conduit 32,67 can facilitate diagnosing shortterm eruption potential. ...
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Magma ascent, storage, and discharge in the trans-crustal magma plumbing system are key to long-term volcanic output and short-term eruption dynamics. Petrological analytics, geodetic deformations and mechanical modeling have shaped the current understanding of magma transport. However, due to the lack of observations, how a distinct magma batch transports from a crystal-rich mush region to a crystal-poor pool with eruptible magma remains enigmatic. Through stacking of tilt and seismic waveform data, we find that episodic long-period tremors (LPTs) located near sea level beneath the Aso volcano are accompanied by a synchronous deformation event, which initiates ~50 seconds before individual LPT event and concludes seconds after. The episodic deformation source corresponds to either an inflation or a deflation event located ~3 km below sea level, with a major volumetric component (50-440 cubic meters per event) and a minor high-angle normal-fault component. We suggest that these deformation events likely represent short-lived, episodic upward transport of discrete magma batches accompanied by high-angle shear failure near the roof of the inferred magma chamber at relatively high temperature, whereas their recurrences, potentially composition dependent, are regulated by the brittle-to-ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long-term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real-time evaluation of upcoming eruptions.
... The filtered dataset is used below to infer volatile sources ad processes deep in the mantle. (Matsumoto et al., 2001;Gurenko et al., 2006;Hopp et al., 2004Hopp et al., , 2007aHopp et al., , 2007bNuccio et al., 2008;Martelli et al., 2014;Oppenheimer et al., 2014;Rizzo et al., 2018). He, Ne and Ar systematics suggest the existence of an atmospheric component in our samples (especially in nodule V -I). ...
Article
We present the first isotopic (noble gases and CO 2) characterization of fluid inclusions coupled to Raman microspectroscopy analyses in mantle xenoliths from Central Mexico, a geodynamically complex area where the Basin and Range extension was superimposed on the Farallon subduction (terminated at 28 Ma). To characterize the isotopic signature of the Central Mexican lithospheric mantle, we focus on fluid inclusions entrapped in mantle xenoliths found in deposits of the Joya Honda maar (JH), a Quaternary monogenetic volcano belonging to the Ventura Espiritu Santo Volcanic Field (VESVF) in the state of San Luis Potosí (central Mexico). Thirteen ultramafic plagioclase-free xenoliths were selected, all exhibiting a paragenesis Ol > Opx > Cpx > > Sp, and being classified as spinel-lherzolites and harzburgites. All xenoliths bring textural evidence of interstitial glass veins bearing dendritic trails of secondary melt and fluid inclusions (composed of silicate glass ± CO 2 ± Mg-Ca carbonates ± pyrite). These are related to pervasive mantle metasomatism driven by carbonate-rich silicate melt. The Ar and Ne systematics reflect mixing between MORB-like upper mantle and atmospheric fluids, the latter interpreted as reflecting a recycled air component possibly inherited from the Farallon plate subduction. The 3 He/ 4 He ratios vary between 7.13 and 7.68 Ra, within the MORB range (7-9 Ra), and the 4 He/ 40 Ar* ratios (0.4-3.11) are similarly close to the expected range of the fertile mantle (1-5). Taken together, these pieces of evidence suggest that (i) either the mantle He budget was scarcely modified by the Farallon plate subduction, and/or (ii) that any (large) crustal contribution was masked by a later metasomatism/refertilization episode, possibly during the subsequent Basin and Range extension. A silicate melt-driven metasomatism/refertilization (revealed by the association between glass veins and fluid inclusions) is consistent with calculated helium residence time for the Mexican lithospheric mantle (20 to 60 Ma) that overlaps the timing of the above geo-dynamic events. We propose that, after the refertilization event (e.g., over the last ~20 Ma), the lithospheric mantle has evolved in a steady-state, becoming slightly more radiogenic. We also estimated 3 He fluxes (0.027-0.080 mol/g), 4 He production rates (340-1000 mol/yr), and mantle CO 2 fluxes (3.93 × 10 7 mol/yr to 1.18 × 10 8 mol/yr) using the helium isotopic values measured in JH mantle xenoliths. Finally, the JH xenoliths exhibit CO 2 / 3 He ratios comparable to those of the upper mantle (from 3.38 × 10 8 to 3.82 × 10 9) but more positive δ 13 C values (between − 1.0 and − 2.7‰), supporting the involvement of a crustal carbonate component. We propose that the metasomatic silicate melts recycled a crustal carbonate component, inherited by the Farallon plate subduction.
... H 2 is one of the most abundant trace species in volcanic emissions and is an essential participant in key redox reactions that take place in magmatic gases since it is intimately interconnected to fO 2 via the water dissociation reaction (e.g. Giggenbach, 1987;Oppenheimer et al., 2014). While CO 2 transport through the hydrothermal system is affected by the occurrence of secondary processes (gas scrubbing by ground-waters and interaction with rocks, decarbonatation processes, biogenic production, etc.), ...
Article
Significant changes in the chemical and isotopic composition of Taal fumarolic gas have been recorded observed before the January 2020 eruption, during the periods 2011 and 2016–2018. Increasing CO2/St, He/CO2, CO/CO2 and CO2/CH4 ratios were recorded during 2011 whereas increasing SO2/H2S, H2/CO2 ratios were recorded during the period 2017–2018. A decreasing on the CO2/CH4 and CO2/St ratios was observed for 2017–2018. These changes are attributed to an increased contribution of magmatic fluids to the hydrothermal system in both periods. Observed changes in H2 and CO contents suggest increases in temperature and pressure in the upper parts of the hydrothermal system of Taal volcano. The ³He/⁴He ratios corrected (Rc/Ra), and δ¹³C of fumarolic gases also increased during the periods 2010–2011 and 2017–2018 before the eruption onset. These variations were produced by two episodes of magmatic intrusion which favored degassing of a gas-rich magma at depth. During the 2010–2011 the magmatic intrusion of volatile-rich magma might have occurred from the mid-crustal storage region at shallower depths producing important he observed changes in pressure and temperature conditions, whereas a new injection of more degassed magma into the deepest zone of the hydrothermal system occurring in 2017–2018 might have favored the accumulation of gases in the subsurface, promoting conditions leading to a phreatic eruption.
... According to Fig. 4, the mineral clarkes of Cl and F are higher and the mineral clarke of S is lower in the Tolbachik fumarole deposits compared to Vulcano. This information is in good agreement with compositions of high-temperature gas emissions of these volcanoes reported in (Oppenheimer et al., 2014) and also with the data on concentrations of rare elements in gaseous samples taken from the Vulcano fumaroles (Cheynet et al., 2000). The authors of the latter paper consider Pb, Bi, As and also Zn, Tl, Cd as the most character-Tol Vul ...
... In addition to their great potential in eruption forecasting, these portable units have revolutionized our understanding of along-arc chemistry of volcanic gases at different regions of the world. Moreover, when combined with remotely sensed SO 2 fluxes, these measurements provide a means to constrain volcanic gas fluxes, especially CO 2 [17][18][19][20][21][26][27][28][29]. ...
Article
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Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005–2015) averaged SO2 flux of ~434 t d−1 for Mt. Garet, we estimate a total volatile output of about 6482 t d−1 (CO2 ~259 t d−1; H2O ~5758 t d−1; H2S ~30 t d−1; H2 ~0.5 t d−1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009–2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes.
... Volcanic and geothermal areas represent the result of the dynamics involving the deeper layers of the earth and resulting in the emission of several gases from volcanic soils. In general, geothermal gases are mainly composed of H 2 O and CO 2 as the most dominant species, and other minor species as the more reduced gases H 2 S, CH 4 , H 2 , CO, and NH 3 (Oppenheimer et al., 2014). The abundance of the latter gases, and consequently their impact to the atmosphere, is strictly related to the energy of the system, the water-rock interactions, gasgas interactions and also to the gas-biota interactions. ...
Article
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Volcanic and geothermal areas are hot and often acidic environments that emit geothermal gasses, including H2, CO and CO2. Geothermal gasses mix with air, creating conditions where thermoacidophilic aerobic H2- and CO-oxidizing microorganisms could thrive. Here, we describe the isolation of two Kyrpidia spormannii strains, which can grow autotrophically by oxidizing H2 and CO with oxygen. These strains, FAVT5 and COOX1, were isolated from the geothermal soils of the Favara Grande on Pantelleria Island, Italy. Extended physiology studies were performed with K. spormannii FAVT5, and showed that this strain grows optimally at 55°C and pH 5.0. The highest growth rate is obtained using H2 as energy source (μmax 0.19 ± 0.02 h–1, doubling time 3.6 h). K. spormannii FAVT5 can additionally grow on a variety of organic substrates, including some alcohols, volatile fatty acids and amino acids. The genome of each strain encodes for two O2-tolerant hydrogenases belonging to [NiFe] group 2a hydrogenases and transcriptome studies using K. spormannii FAVT5 showed that both hydrogenases are expressed under H2 limiting conditions. So far no Firmicutes except K. spormannii FAVT5 have been reported to exhibit a high affinity for H2, with a Ks of 327 ± 24 nM. The genomes of each strain encode for one putative CO dehydrogenase, belonging to Form II aerobic CO dehydrogenases. The genomic potential and physiological properties of these Kyrpidia strains seem to be quite well adapted to thrive in the harsh environmental volcanic conditions.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
Chapter
Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.
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The study of the chemical composition of volcanic emissions is an important method for obtaining information about volcanic systems and providing indirect and unique insights into magmatic processes. However, there is a non-negligible risk associated with sampling directly at volcanic craters or maintaining geochemical monitoring stations at such locations. Spectroscopic remote sensing methods, in turn, can measure only a few species. Here, drones offer the opportunity to bring measurement systems to the scene. Standard parameters that are commonly measured are SO 2 and CO 2 concentrations, as well as a number of meteorological parameters. The in-flight transmission of data by radio telemetry plays an important role, since visual localization of the volcanic plume from a distance of several kilometers is practically impossible. Until now, larger and quite cost-intensive drones have been used for this purpose, which must first be transported to the site of operation at great expense. Here, we present the development and successful deployment of a very small drone system (empty weight < 0.9 kg) for chemical characterization of volcanic plumes that can be easily transported on foot to difficult-to-access terrain and, moreover, requires only minimal flight and administrative preparations for operation as an aerial observation platform.
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This chapter provides an overview of the usefulness of in situ measurements of volcanic gases as a tool for volcanological monitoring. It describes ground and satellite remote sensing techniques for gas monitoring. The chapter provides to basic concepts, the in situ techniques used to monitor the composition and fluxes of the main types of volcanic fluids. It presents an example of a volcanic fluid study that has contributed to a better understanding of degassing processes and volcano behavior. The chemical composition of volcanic gases shows significant variability. Melt inclusions (MIs) allow a study of the volatile phases associated with silicate fluid. By comparing the concentrations of volatiles in MIs and matrix glass, and knowing the volume of magma emitted, it is possible to estimate the amount of each volatile species degassed.
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This chapter describes how volcanic emissions into the troposphere and stratosphere affect aerosol properties, radiation, and climate. It begins by describing aerosol and precursor gas emissions from passive degassing and volcanic eruptions, including a time history of emissions over the satellite era since 1978. It describes how records of volcanism and volcanic effects on climate can be reconstructed from ice cores, tree rings, and written historical records. It then describes how volcanic emissions affect aerosol physical and optical properties and how these alter atmospheric radiation and global temperature. The chapter concludes by outlining the status of models and the challenges in using them to quantitatively link volcanic sulfate deposition records in ice cores to their climatic effects.
Article
The Multi-GAS, a robust and low-cost instrument for real-time in-situ gas measurements, has previously been used mainly for compositional measurements of active volcanic plumes. Here we demonstrate novel use of a specially designed Multi-GAS instrument adapted to low temperature degassing areas. We performed compositional measurements in the Eastern Carpathians on dry and bubbling gas emissions using a sensor kit that allows measurement of CO2, CH4 and H2S (three major components of low-temperature hydrothermal/volcanic manifestations). Our results demonstrate good agreement between Multi-GAS measurements and independently obtained CO2 concentrations from gas chromatography. We also provide some novel H2S information for some anomalous sites, which we relate to possible alteration processes of sulphide minerals. The use of Multi-GAS in such environments could open new possibilities for data collection at non-volcanic areas and exploration of mineral resources. Moreover, it can also be a useful tool in exploration surveys to select the best sampling sites for more detailed laboratory measurements.
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The Early Cretaceous Jehol Biota evolution has remarkable spatiotemporal correlation with the destruction of the North China craton though the coupling mechanism remains enigmatic. The craton destruction was accompanied by intense magmatic activity and the released volatiles and nutrients might have had climatic and environmental impacts on the biotic evolution. In this study, we investigated the mentioned hypothetical causal link by determining concentrations and total emissions of volatile elements (S, F, Cl) and bulk‐rock P contents of volcanic rocks that were erupted during the pre‐flourishing, flourishing and post‐flourishing stages of the Jehol Biota. Our results show that the volcanism near the flourishing stage has lower S (1,083–2,370 ppm), Cl (1,277–5,608 ppm) and higher P2O5 contents (0.48–0.84 wt.%) than that in the non‐flourishing stages with S of 1,991–3,288 ppm, Cl of 7,915–12,315 ppm and P2O5 of 0.17–0.23 wt.%. Fluorine contents in the three stages vary from 893 to 3,746 ppm. The total volatile emissions are minor in the flourishing stage (1–14 Gt S, 0.6–10 Gt Cl, 0.6–9 Gt F) but elevated in the non‐flourishing stages (2–766 Gt S, 4–1,168 Gt Cl, 1–175 Gt F). Our data suggest that regional climatic and environmental impacts of volcanism in the non‐flourishing stages probably hindered the species diversification. The high P flux released from lithospheric mantle‐derived lavas during the peak time of craton destruction might have enhanced primary productivity and contributed to the flourishing of the Jehol Biota. Our study provides insights into the relationship between the biosphere and deep geodynamic processes driven by volcanism.
Article
The exsolution, rise, expansion, and separation of volatiles from magma provide the driving force behind both effusive and explosive volcanic eruptions. The field of volcanic gas geochemistry therefore plays a key role in understanding volcanism. In this article, we summarize the most important findings of the past few decades and how these shape today’s understanding of volcanic degassing. We argue that the recent advent of automated, continuous geochemical monitoring at volcanoes now allows us to track activity from unrest to eruption, thus providing valuable insights into the behavior of volatiles throughout the entire sequence. In the next 10 years, the volcanological community stands to benefit from the expansion of geochemical monitoring networks to many more active volcanoes. This, along with technical advances in instrumentation and in particular the increasing role that unoccupied aircraft systems (UAS) and satellite-based observations are likely to play in collecting volcanic gas measurements, will provide a rich dataset for testing hypotheses and developing diagnostic tools for eruption forecasts. The use of consistent, well-documented analytical methods and ensuring free, public access to the collected data with few restrictions will be most beneficial to the advancement of volcanic gas science. © 2022, This is a U.S. government work and not under copyright protection in the U.S.; foreign
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Plain Language Summary Understanding volcanoes dynamics is critical in evaluating volcanic risks and fundamental for the Earth system comprehension. The behavior of trace elements and their isotopes in fumaroles can be explored for evaluating imminent volcanic actions. Because of large crystal‐chemical similarities of Zr and Hf in rocks and minerals, the Zr‐Hf ratio is nearly constant to 36.6 ± 2.9 in meteorites and primitive rocks (“chondritic” reference.) We found that fumarole fluids at 1060°C–1084°C have sub‐chondritic Zr/Hf signature (Zr/Hf between 24 and 29) when fast degassing of magma occurs while, fumarole fluids of lower temperature have super‐chondritic or chondritic Zr/Hf values according to the intensity of rock‐fluid interaction processes. The Zr/Hf ratio of fumarole fluids can be used as a new tool for volcanic risk evaluation as possible tracer of fast magmatic arriving.
Article
The sulfur cycle at convergent margins remains poorly constrained yet is fundamentally important for understanding the redox state of Earth's reservoirs and the formation of ore deposits. In this study we investigate the sulfur isotope composition of high temperature volcanic gases emitted from the Nicaraguan (average of +4.8 ± 1.3‰) and Costa Rican (average of +2.3 ± 1.3‰) arc segments contributing to emissions from the Southern Central American Volcanic Arc (SCAVA; average of +3.8 ± 1.7‰). Along-arc variations in geochemical tracers at SCAVA are widely accepted to reflect variations in subduction parameters and deep fluid sources and correlations between these parameters and gas S isotope compositions are observed. These correlations suggest that gas emissions are sourced from a mixture of mantle S with δ³⁴S ~ 0‰ and isotopically heavy slab-derived sulfur with δ³⁴S ~ +8‰. We employ Monte Carlo mass balance modeling to constrain S inputs to the subduction zone and relative contributions from mantle and slab to arc gas emissions. The models indicate that bulk subduction input in Nicaragua has a S isotope composition of +1.4 ± 0.5‰ compared to −0.2 ± 0.4‰ in Costa Rica, requiring preferential release of isotopically heavy oxidized S from the slab to explain the relatively high δ³⁴S observed in arc outputs. We show that the flux of S from the slab is sufficient to oxidize the entire mantle wedge within the lifetime of the arc, indicating that S is a primary oxidizing agent in subduction zones. Furthermore, the preferential removal of heavy S from the slab requires retention of isotopically light S in the residual slab. Subduction-scale fractionation of S isotopes is fundamentally important in explaining why Earth's bulk surface reservoirs are isotopically positive.
Article
The balance between the amount of gas coexisting with mantle-derived magmas at depth and that emitted during intereruptive phases may play a key role in the eruptive potential of volcanoes. Taking the December 2018 eruption at Mt. Etna volcano as a case study, we discuss the geochemical data streams observed. The signals indicate a long-lasting prelude stage to eruption, starting in 2017 and involving magma-fluid accumulation in the deep (>7 km bsl) reservoir, followed by pressure buildup in the system at intermediate depth (5 to 2 km bsl), 6 to 7 months before the eruption. A brief preeruptive phase marks the pressurization at 2 to 3 km below the craters. By comparing the magma and fluid recharge at depth to the measured volcanic degassing from the plume, we provide evidence that Mt. Etna was in a state of extreme overpressurization in the weeks before the onset of the eruption.
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Carbon in the upper mantle controls incipient melting of carbonated peridotite and so acts as a critical driver of plate tectonics. The carbon-rich melts that form control the rate of volatile outflux from the Earth’s interior, contributing to climate evolution over geological times. However, attempts to constrain the carbon concentrations of the mantle source beneath oceanic islands and continental rifts is complicated by pre-eruptive volatile loss from magmas. Here, we compile literature data on magmatic gases, as a surface expression of the pre-eruptive volatile loss, from 12 oceanic island and continental rift volcanoes. We find that the levels of carbon enrichment in magmatic gases correlate with the trace element signatures of the corresponding volcanic rocks, implying a mantle source control. We use this global association to estimate that the mean carbon concentration in the upper mantle, down to 200 km depth, is approximately 350 ppm (range 117–669 ppm). We interpret carbon mantle heterogeneities to reflect variable extents of mantle metasomatism from carbonated silicate melts. Finally, we find that the extent of carbon enrichment in the upper mantle positively correlates with the depth at which melting starts. Our results imply a major role of carbon in driving melt formation in the upper mantle. The carbon concentration of Earth’s upper mantle increases with depth, indicating a role for carbon in melt formation, according to data on magmatic gases and volcanic rocks from ocean island and continental rift settings around the world.
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Masaya (Nicaragua, 12.0∘ N, 86.2∘ W; 635 m a.s.l.) is one of the few volcanoes hosting a lava lake, today. This study has two foci: (1) discussing the state of the art of long-term SO2 emission flux monitoring with the example of Masaya and (2) the provision and discussion of a continuous data set on volcanic gas data with a large temporal coverage, which is a major extension of the empirical database for studies in volcanology as well as atmospheric bromine chemistry. We present time series of SO2 emission fluxes and BrO/SO2 molar ratios in the gas plume of Masaya from March 2014 to March 2020 – covering the three time periods (1) before the lava lake appearance, (2) a period of high lava lake activity (November 2015 to May 2018), and (3) after the period of high lava lake activity. For these three time periods, we report average SO2 emission fluxes of (1000±200), (1000±300), and (700±200) t d−1 and average BrO/SO2 molar ratios of (2.9±1.5)×10-5, (4.8±1.9)×10-5, and (5.5±2.6)×10-5. Our SO2 emission flux retrieval is based on a comprehensive investigation of various aspects of spectroscopic retrievals, the wind conditions, and the plume height. We observed a correlation between the SO2 emission fluxes and the wind speed in the raw data. We present a partial correction of this artefact by applying dynamic estimates for the plume height as a function of the wind speed. Our retrieved SO2 emission fluxes are on average a factor of 1.4 larger than former estimates based on the same data. Further, we observed different patterns in the BrO/SO2 time series: (1) an annual cyclicity with amplitudes between 1.4 and 2.5×10-5 and a weak semi-annual modulation, (2) a step increase by 0.7×10-5 in late 2015, (3) a linear trend of 1.4×10-5 per year from November 2015 to March 2018, and (4) a linear trend of -0.8×10-5 per year from June 2018 to March 2020. The step increase in 2015 coincided with the lava lake appearance and was thus most likely caused by a change in the magmatic system. We suggest that the cyclicity might be a manifestation of meteorological cycles. We found an anti-correlation between the BrO/SO2 molar ratios and the atmospheric water concentration (correlation coefficient of −0.47) but, in contrast to that, neither a correlation with the ozone mixing ratio (+0.21) nor systematic dependencies between the BrO/SO2 molar ratios and the atmospheric plume age for an age range of 2–20 min after the release from the volcanic edifice. The two latter observations indicate an early stop of the autocatalytic transformation of bromide Br− solved in aerosol particles to atmospheric BrO.
Conference Paper
Volcanoes are one of the great forces of the natural world. The gases they release can reveal information about the world below us, from the structure of the planet, to the risk of an imminent eruption. Sampling these gases however is often difficult and extremely dangerous - high temperatures, hazardous gases, steep terrain and remoteness all make collecting samples a challenging endeavour. Unoccupied Aerial Vehicles (UAVs) can help reduce the risks and difficulties of measuring and sampling these gases, enabling studies of volcanic systems that were otherwise inaccessible. This paper presents the first known effort to design, develop and field test a UAV-borne Gas Capture System (UGCS) for volcanic fumarole sampling. This work includes the development of a sampling probe deployment mechanism, sample canister selection, payload-to-UAV interfacing, and a light-weight visual/thermal camera package. Operationally, the intricacies of placing a sample probe into a small fumarole opening are examined, as are the hazards of flying a UAV with a suspended load.
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Mass-independent fractionation of sulfur isotopes (MIF-S)—as recorded primarily in pre-2.5 billion years ago (Ga) sedimentary rocks—has been interpreted as evidence of photolysis of volcanic SO2 in an anoxic troposphere. Here, I present thermodynamic and kinetic calculations, combined with data on the geology, mineralogy and chemical and isotopic compositions of modern and Archaean (3.8–2.5 Ga) aged volcanic samples from different tectonic settings, to examine early Earth’s sulfur cycle. Based partly on the similarities between submarine hydrothermal deposits and arc volcanic rocks in pyrite (FeS2) abundances and sulfur isotopic compositions (for example, the presence of both positive and negative δ34S values), I conclude that degassing of sulfur (mostly as SO2) into the atmosphere has been carried out primarily by subaerial eruptions of oxidized, arc-like magmas since at least 3.5 Ga. The generation of volcanic SO2 requires plate tectonics and the involvement of sulfate-rich seawater, which requires large exposed lands and an oxygenated atmosphere. I propose that the MIF-S signatures in sedimentary rocks were created by ultraviolet photochemical reactions between SO2 from explosive volcanic eruptions and O2 in the stratosphere, above an oxygen-rich troposphere, or by high-temperature reactions between organic compounds and sulfate in the oceans. Formation of mass-independent isotope fractionation of sulfur signatures recorded in Archaean sedimentary rocks could have occurred in an oxygen-rich atmosphere, according to thermodynamic and kinetic calculations and analysis of Earth’s early sulfur cycle.
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Volcanic degassing of planetary interiors has important implications for their corresponding atmospheres. The oxidation state of rocky interiors affects the volatile partitioning during mantle melting and subsequent volatile speciation near the surface. Here we show that the mantle redox state is central to the chemical composition of atmospheres while factors such as planetary mass, thermal state, and age mainly affect the degassing rate. We further demonstrate that mantle oxygen fugacity has an effect on atmospheric thickness and that volcanic degassing is most efficient for planets between 2 and 4 Earth masses. We show that outgassing of reduced systems is dominated by strongly reduced gases such as \(\text {H}_{2}\), with only smaller fractions of moderately reduced/oxidised gases (\(\text {CO}\), \(\text {H}_{2}\text {O}\)). Overall, a reducing scenario leads to a lower atmospheric pressure at the surface and to a larger atmospheric thickness compared to an oxidised system. Atmosphere predictions based on interior redox scenarios can be compared to observations of atmospheres of rocky exoplanets, potentially broadening our knowledge on the diversity of exoplanetary redox states.
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The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm<sup>−3</sup> at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions.
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We investigate the roles of climate forcings and chaos (unforced variability) in climate change via ensembles of climate simulations in which we add forcings one by one. The experiments suggest that most interannual climate variability in the period 1979-1996 at middle and high latitudes is chaotic. But observed SST anomalies, which themselves are partly forced and partly chaotic, account for much of the climate variability at low latitudes and a small portion of the variability at high latitudes. Both a natural radiative forcing (volcanic aerosols) and an anthropogenic forcing (ozone depletion) leave clear signatures in the simulated climate change that are identified in observations. Pinatubo aerosols warm the stratosphere and cool the surface globally, causing a tendency for regional surface cooling. Ozone depletion cools the lower stratosphere, troposphere and surface, steepening the temperature lapse rate in the troposphere. Solar irradiance effects are small, but our model is inadequate to fully explore this forcing. Well-mixed anthropogenic greenhouse gases cause a large surface warming that, over the 17 years, approximately offsets cooling by the other three mechanisms. Thus the net calculated effect of all measured radiative forcings is approximately zero surface temperature trend and zero heat storage in the ocean for the period 1979-1996. Finally, in addition to the four measured radiative forcings, we add an initial (1979) disequilibrium forcing of+0.65 W/m2. This forcing yields a global surface warming of about 0.2°C over 1979-1996, close to observations, and measurable heat storage in the ocean. We argue that the results represent evidence of a planetary radiative imbalance of at least 0.5 W/m2; this disequilibrium presumably represents unrealized warming due to changes of atmospheric composition prior to 1979. One implication of the disequilibrium forcing is an expectation of new record global temperatures in the next few years. The best opportunity for observational confirmation of the disequilibrium is measurement of ocean temperatures adequate to define heat storage.
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This review gives an overview of the estimates of volatile emissions from arc and mid-ocean ridge volcanoes to the atmosphere and hydrosphere with particular focus on H 2 O, CO 2 , N 2 , Cl and F. The gas compositions of high temperature (>500°C) fumaroles are compiled and used to derive magmatic H 2 O/SO 2 , CO 2 /SO 2 , HCl/SO 2 and HF/SO 2 ratios on an arc-by-arc basis to obtain new estimates of major volatile fluxes from arcs globally. The estimate of F flux from arcs is two orders of magnitude smaller than the amount of F released from mid ocean ridges whereas the arc Cl flux exceeds the ridge flux. An important observation is that globally the water budget of subduction zones seems to be balanced and the amount of water degassed through arc volcanism is within the estimates of the amount of water released from the slab below the volcanic front. Recent work that focused on the Central American arc shows that detailed knowledge of the subduction input compositions, coupled with gas emission studies is critical to further constrain the fate of volatiles during the subduction processes.
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Experiments were conducted to determine the solubilities of H 2O and CO 2 and the nature of their mixing behavior in basaltic liquid at pressures and temperature relevant to seqfloor eruption. Mid-ocean ridge basaltic (MORB) liquid was equilibrated at 1200°C with pure H 2O at pressures of 176-717 bar and H 2O-CO 2 vapor at pressures up to 980 bar. Concentrations and speciation of H 2O and CO 2 dissolved in the quenched glasses were measured using IR spectroscopy. Molar absorptivities for the 4500 cm -1 band of hydroxyl groups and the 5200 and 1630 cm -1 bands of molecular water are 0{dot operator}67±0{dot operator}03, 0{dot operator}62±0{dot operator}07, and 25±3 l/mol-cm, respectively. These and previously determined molar absorptivities for a range of silicate melt compositions correlate positively and linearly with the concentration of tetrahedral cations (Si+Al).The speciation of water in glass quenched from vapor-saturated basaltic melt is similar to that determined by Silver & Stolper (Journal of Petrology 30, 667-709, 1989) in albitic glass and can be fitted by their regular ternary solution model using the coefficients for albitic glasses. Concentrations of molecular water measured in the quenched basaltic glasses are proportional to f H 2O in all samples regardless of the composition of the vapor, demonstrating that the activity of molecular water in basaltic melts follows Henry's law at these pressures. A best fit to our data and existing higher-pressure water solubility data (Khitarov et al., Geochemistry 5, 479-492, 1959; Hamilton et al., Journal of Petrology 5, 21-39, 1964), assuming Henrian behavior for molecular water and that the dependence of molecular water content on total water content can be described by the regular solution model, gives estimates for the V o,mH2O of 12±1 cm 3/mol and for the 1-bar water solubility of 0{dot operator}11 wt%.Concentrations of CO 2 dissolved as carbonate in the melt for pure CO 2-saturated and mixed H 2O-CO 2-saturated experiments are a simple function of f CO2 These results suggest Henrian behavior for the activity of carbonate in basaltic melt and do not support the widely held view that water significantly enhances the solution of carbon dioxide in basaltic melts. Using a ΔV o,mr of 23 cm 3/mol (Pan et al., Geochimica et Cosmochimica Acta 55, 1587-1595, 1991), the solubility of carbonate in the melt at 1 bar and 1200°C is 0{dot operator}5 p.p.m. Our revised determination of CO 2 solubility is ∼20% higher than that reported by Stolper & Holloway (Earth and Planetary Science Letters 87, 397-408, 1988).
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An extensive electron microprobe survey of amphibole compositions in the Fish Canyon magma (2146 analyses), more than 80% of which are from high-resolution (<10 μm steps) core-to-rim traverses across large euhedral phenocrysts, provides: (1) temporal constraints on the immediately pre-eruptive P-T-fH2O evolution of the magma, and (2) a means of evaluating recent calibrations of the Al-in-hornblende barometer (Anderson and Smith 1995; hereafter AS 1995) and thermometers (Blundy and Holland 1990: thermometers A and B of Holland and Blundy 1994: hereafter BH 1990, HB 1994TA, and HB 1994TB). Hornblende phenocrysts are variable for most major elements (e.g., 5-9 wt% Al2O3 and 44-50 wt% SiO2). This compositional range is controlled by two major temperature-sensitive coupled substitutions. Approximately 50% of the total Al variation (∼0.8 atoms per formula unit = apfu) is due to the edenite exchange [TSi + A□ = TAl + A(Na + K)] and another 25-30% is the consequence of a Ti-Tschermak exchange (TSi + M1-M3 Mn = TAl + AM1-M3Ti). In contrast, the pressure-sensitive Al-Tschermak substitution (TSi + M1-M3 Mg = TAl + M1-M3Al) did not play a significant role, as M1-M3Al does not correlate with TAl and is always <0.2 apfu. In order to constrain the ranges of absolute P and T over which these hornblendes crystallized and to assess the sensitivity of the recent thermo-barometric algorithms of BH1990, HB1994TA (requiring silica saturation), HB 1994TB (not requiring silica saturation) and AS 1995, we have calculated pressures and temperatures for two selected populations of analyses wherein Al2O3 contents are within analytical error (5.95 to 6.05 wt% Al2O3, N = 78 and 7.7 to 7.8 wt% Al2O3, N = 40). The barometric formulation of AS 1995 gives a mean pressure of 2.24 ± 0.05 for the high-Al population at 760 °C. which is indistinguishable from the 2.4 ± 0.5 kbar estimate of Johnson and Rutherford (1989a). A high sensitivity to temperature at low P is suggested by the geologically implausibly shallow depths calculated for the low-Al population (<1 kbar at 760 °C). The three thermometric formulations give reasonable results between 706 and 814 °C, but the HB 1994TA calibration gives a mean temperature higher by ~50 °C and is more sensitive to small analytical differences (~100 °C spread for each population). HB 1994TB is considered the most reliable calibration of the Al-in-hornblende thermometer as it most precisely reproduces T estimates determined by independent methods. Nine out of 14 traverses across large phenocrysts from the Fish Canyon magma display rimward increases in TAl, A(Na + K), and M1-M3Ti, compensated by decreases in TSi, and M1-M3Mn. Using the HB 1994TB algorithm, the low-Al population, typical of near-core compositions, gives a mean temperature of ~0715 °C, which is ~35-45 °C above the water-saturated granite solidus at 2-2.5 kbar. The high-Al population, representing the average rim composition, gives a value around 760 °C, which is indistinguishable from independent T determinations using coexisting Fe-Ti oxides and Qtz-Mag oxygen isotope thermometry. These profiles suggest that Fish Canyon hornblendes crystallized during near- isobaric reheating over a temperature range of ~40 °C, which is consistent with our model of rejuvenation and remobilization of a pre-existing near-solidus crystal mush of batholithic dimensions via shallow intrusion of more mafic magma (Bachmann et al. 2002). Crystallization of hornblende from a high-SiO2, low-MgO melt during reheating requires an open system, in which both heat and mass, in particular volatiles, are transferred from the underlying mafic magma.
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Solubility experiments were conducted with forty-one aluminosilicate rock compositions to determine how extensively Cl dissolves in hydrous chloride melt- ± vapor-saturated silicate melts containing low to moderate water contents at 2000 bars. Chlorine solubility in most silicate melts is dominated by the abundances of Mg ≈ Ca > Fe > Na > K > network-forming Al > Li ≈ Rb ≈ Cs. but Ti, F, and P also have strong influences. The relationship of composition to Cl solubility is more complex in peraluminous and peralkaline felsic melts, because network-modifying Al, Na, and K have a greater influence than their network-forming counterparts. Also, the effects of Ca, Mg, and Al in mafic melts characterized by high (Ca + Mg + Al)/(Na + K + Li) are much greater than their effects in silica-enriched melts. Association coefficients that express the influence of each ion on Cl solubility were determined, and the solubility data and coefficients were coefficients were employed to develop a model that predicts Cl solubility at 2000 bars for water-undersaturated melts ranging from rhyolite to basalt. The coefficients were also used to investigate the predominant chloride complexes in melt, and the bulk of the solubility data are consistent with the interaction of Cl with alkaline-earth metals that provide charge balance for network-forming Al. The Cl solubility model is applied to Mt. Somma-Vesuvius magmas as they evolved from phonotephrite to phonolitic compositions, via fractional crystallization, to investigate the role of Cl in magmatic degassing. The results clearly demonstrate that Cl solubility was dramatically reduced by subtle changes in melt composition. Decreasing abundances of Ca, Mg, and Fe in the residual melt induced a dramatic reduction in Cl solubility that occured simultaneously with gradual increases in the abundance of volatiles in melt due to crystallization of volatile-free minerals. The increasing abundance of volatiles and concurrent reduction in Cl solubility may have forced the exsolution of a hydrous chloride melt directly from the Cl-enriched mafic magmas. It is likely that the exsolution of hydrous chloride melt may occur in other Cl-enriched magmas, because Cl solubility depends so strongly on melt composition.
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The Evolution of the Igneous Rocks, by N. L. Bowen, appeared in 1928 and had a profound influence on later generations of petrologists. Drawing on his series of lectures at Princeton University in the spring of 1927, Dr. Bowen identified, outlined, and applied the principles of physical chemistry relevant to petrological processes. Whereas the major petrochemical questions he discussed are still relevant today, the answers appear to change with time. The purpose of the present volume is to provide an updated view of those questions, in the light of almost fifty years of accumulated observations, using the principles Bowen set forth.
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We present solution models for the rhyolite–H_2O–CO_2 and basalt–H_2O–CO_2 systems at magmatic temperatures and pressures below ∼5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within Microsoft® Excel (Office’98 and 2000). The series of macros, entitled VolatileCalc, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H_2O and CO_2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H_2O and CO_2 vapors at magmatic temperatures. The basalt–H_2O–CO_2 macros in VolatileCalc are capable of calculating melt–vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt–vapor systems for pressures below 5000 bar.
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