Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica
TL;DR: In this paper, the authors examined the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake.
About: This article is published in Earth and Planetary Science Letters.The article was published on 2011-06-15 and is currently open access. It has received 126 citations till now. The article focuses on the topics: Erebus & Strombolian eruption.
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TL;DR: In this paper, the authors show that the CO 2 and S concentrations within an included melt decrease with progressive diffusive H 2 O loss, and propose that this occurs due to dehydration-induced changes to the internal pressure of the inclusion.
192 citations
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...(Oppenheimer et al., 2011), Iceland (Nichols and Wysoczanski, 2007)....
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TL;DR: This paper reviewed the causes of variability in sulfur abundance and speciation in different geodynamic contexts; the measurement of sulfur emissions from volcanoes; links between subsurface processes and surface observations; sulfur chemistry in volcanic plumes; and the consequences of sulfur degassing for climate and the environment.
Abstract: Despite its relatively minor abundance in magmas (compared with H2O and CO2), sulfur degassing from volcanoes is of tremendous significance. It can exert substantial influence on magmatic evolution (potentially capable of triggering eruptions); represents one of the most convenient opportunities for volcano monitoring and hazard assessment; and can result in major impacts on the atmosphere, climate and terrestrial ecosystems at a range of spatial and temporal scales. The complex behavior of sulfur in magmas owes much to its multiple valence states (−II, 0, IV, VI), speciation (e.g., S2, H2S, SO2, OCS and SO3 in the gas phase; S2−, SO42− and SO32− in the melt; and non-volatile solid phases such as pyrrhotite and anhydrite), and variation in stable isotopic composition (32S, 33S, 34S and 36S; e.g., Metrich and Mandeville 2010). Sulfur chemistry in the atmosphere is similarly rich involving gaseous and condensed phases and invoking complex homogeneous and heterogeneous chemical reactions. Sulfur degassing from volcanoes and geothermal areas is also important since a variety of microorganisms thrive based on the redox chemistry of sulfur: by reducing sulfur, thiosulfate, sulfite and sulfate to H2S, or oxidizing sulfur and H2S to sulfate (e.g., Takano et al. 1997; Amend and Shock 2001; Shock et al. 2010). Understanding volcanic sulfur degassing thus provides vital insights into magmatic, volcanic and hydrothermal processes; the impacts of volcanism on the Earth system; and biogeochemical cycles. Here, we review the causes of variability in sulfur abundance and speciation in different geodynamic contexts; the measurement of sulfur emissions from volcanoes; links between subsurface processes and surface observations; sulfur chemistry in volcanic plumes; and the consequences of sulfur degassing for climate and the environment.
### Geodynamics and the geochemical behavior of sulfur
The …
172 citations
Cites background from "Mantle to surface degassing of alka..."
...This provides significant insights into the dynamics of magma transport and degassing of magma (e.g., Allard et al. 2005; Burton et al. 2007b; Oppenheimer et al. 2009, 2011)....
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TL;DR: In this paper, the authors track the redox evolution of an alkaline magmatic suite at Erebus volcano, Antarctica, from the mantle to the surface, using X-ray absorption near-edge structure (XANES) spectroscopy at the iron and sulphur K-edges.
112 citations
Cites background or methods or result from "Mantle to surface degassing of alka..."
...Plot of H2O concentration (in wt%; determined by FTIR (Oppenheimer et al., 2011)) compared to Fe 3+ /Fe ratio determined by Fe K-edge XANES....
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...The red star represents the lava lake conditions as determined by surface gas measurements (Oppenheimer et al., 2011; Moussallam et al., 2012)....
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...In an earlier study of Erebus (Oppenheimer et al., 2011), a linear decrease of FeO/Fe2O3 with decreasing pressure (from NNO+0....
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...This results in slightly shallower estimates of entrapment depths for evolved compositions than previously reported (Oppenheimer et al., 2011) (Figure 3C)....
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...Figure 6: Plot of Fe 3+ /Fe ratio determined by Fe K-edge XANES compared to measured sulphur contents (Oppenheimer et al., 2011) for each melt inclusion....
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01 Jan 2014
TL;DR: 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 as mentioned in this paper.
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.
105 citations
TL;DR: High‐frequency gas monitoring is used to track the behavior of the Turrialba Volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions, showing a remarkable shift to purely magmatic composition during the second eruptive period.
Abstract: Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San Jose. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/S-total>4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is similar to 8-10km deep, whereas the shallow magmatic gas source is at similar to 3-5km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000T/d SO2 and H2S/SO2>1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2<0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.
97 citations
Cites background from "Mantle to surface degassing of alka..."
...…monitoring of volcanic gas compositions allowed by technological advances in the last decade is repeatedly showing the value of these measurements in forecasting and understanding volcanic eruptions [Aiuppa et al., 2007; Burton et al., 2007; de Moor et al., 2016; Oppenheimer et al., 2011]....
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References
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TL;DR: Papale et al. as mentioned in this paper applied thermodynamic equilibrium between gaseous and liquid volatile components to model the volatile saturation surface in H 2 O−CO 2 -silicate melt systems.
491 citations
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...Papale et al. (2006) showed that H2O–CO2 saturation modelling in melts produces uncertainties in pressure (P) retrieval of up to 20% at 20 kbar, pertaining to the solubility database over which the model was calibrated....
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...S system, and incorporated: (i) a regular mixture approach to H2O–CO2–melt saturation (Papale et al., 2006); (ii) polymeric treatment of silicate melts for computation of sulphur solubility and speciation ( [Moretti and Ottonello, 2005] and [Moretti and Papale, 2004]), and compatible oxidation…...
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...Geol., 174 (2001), pp. 157–179 Papale et al., 2006 P. Papale, R. Moretti, D. Barbato The compositional dependence of the saturation surface of H2O + CO2 fluids in silicate melts Chem....
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...Application of the multi-component H2O–CO2 saturation model of Papale et al. (2006) to each sample yields saturation pressures up to 8 kbar for DVDP basanites, corresponding to depths of ~ 25–30 km and therefore in the mantle....
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TL;DR: In this article, the authors decipher the origin and mechanisms of the second eruption from the composition and volatile (H2O, CO2, S, Cl) content of olivine-hosted melt inclusions in explosive products from its south flank vents.
Abstract: [1] Two unusual, highly explosive flank eruptions succeeded on Mount Etna in July August 2001 and in October 2002 to January 2003, raising the possibility of changing magmatic conditions. Here we decipher the origin and mechanisms of the second eruption from the composition and volatile (H2O, CO2, S, Cl) content of olivine-hosted melt inclusions in explosive products from its south flank vents. Our results demonstrate that powerful lava fountains and ash columns at the eruption onset were sustained by closed system ascent of a batch of primitive, volatile-rich (≥4 wt %) basaltic magma that rose from ≥10 km depth below sea level (bsl) and suddenly extruded through 2001 fractures maintained opened by eastward flank spreading. This magma, the most primitive for 240 years, probably represents the alkali-rich parental end-member responsible for Etna lavas' evolution since the early 1970s. Few of it was directly extruded at the eruption onset, but its input likely pressurized the shallow plumbing system several weeks before the eruption. This latter was subsequently fed by the extrusion and degassing of larger amounts of the same, but slightly more evolved, magma that were ponding at 6–4 km bsl, in agreement with seismic data and with the lack of preeruptive SO2 accumulation above the initial depth of sulphur exsolution (∼3 km bsl). We find that while ponding, this magma was flushed and dehydrated by a CO2-rich gas phase of deeper derivation, a process that may commonly affect the plumbing system of Etna and other alkali basaltic volcanoes.
310 citations
TL;DR: In this article, the authors present some of the current petrological techniques that can be used for studying eruptive products and for constraining key magmatic variables such as pressure, temperature, and volatile content.
Abstract: Explosive volcanic eruptions constitute a major class of natural hazard with potentially profound economic and societal consequences. Although such eruptions cannot be prevented and only rarely may be anticipated with any degree of accuracy, better understanding of how explosive volcanoes work will lead to improved volcano monitoring and disaster mitigation. A major goal of modern volcanology is linking of surface-monitored signals from active volcanoes, such as seismicity, ground deformation and gas chemistry, to the subterranean processes that generate them. Because sub-volcanic systems cannot be accessed directly, most of what we know about these systems comes from studies of erupted products. Such studies shed light on what happens underground prior to and during eruptions, thereby providing an interpretative framework for post hoc evaluation of monitoring data. The aim of this review is to present some of the current petrological techniques that can be used for studying eruptive products and for constraining key magmatic variables such as pressure, temperature, and volatile content. We first review analytical techniques, paying particular attention to pitfalls and strategies for analyzing volcanic samples. We then examine commonly used geothermometry schemes, evaluating each by comparison with experimental data not used in the original geothermometer calibrations. As there are few mineral-based geobarometers applicable to magma storage regions, we review other methods used to determine pre-eruptive magma equilibration pressures. We then demonstrate how petrologically-constrained parameters can be compared to the contemporaneous monitoring record. These examples are drawn largely from Mount St. Helens volcano, for which there are abundant petrological and monitoring data. However, we emphasize that our approaches can be applied to any number of active volcanoes worldwide. Finally, we illustrate the application of these techniques to two different types of magmatic systems—large silicic magma chambers and small intermediate-composition magma storage regions—with particular focus on the combined evolution of melt …
301 citations
TL;DR: In this article, the results of two years of real-time observation of H2O, CO2, and SO2 in volcanic gases from Mount Etna volcano were unambiguously demonstrated that increasing CO2/SO2 ratios can allow detection of pre-eruptive degassing of rising magmas.
Abstract: It is generally accepted, but not experimentally proven, that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data. By discussing the results of two years of real-time observation of H2O, CO2, and SO2 in volcanic gases from Mount Etna volcano, we unambiguously demonstrate that increasing CO2/SO2 ratios can allow detection of the pre-eruptive degassing of rising magmas. Quantitative modeling by the use of a saturation model allows us to relate the pre-eruptive increases of the CO2/SO2 ratio to the refilling of Etna's shallow conduits with CO2-rich deep-reservoir magmas, leading to pressurization and triggering of eruption. The advent of real-time observations of H2O, CO2, and SO2, combined with well-constrained models of degassing, represents a step forward in eruption forecasting.
287 citations
"Mantle to surface degassing of alka..." refers background in this paper
...The first scenario is reminiscent of trends observed at open-conduit volcanoes such as Stromboli and Etna ( [Aiuppa et al., 2007], [Aiuppa et al., 2010] and [Shinohara et al., 2008]); in the Erebus case, the explosive gas composition can be manufactured with ~ 50 wt.% of the deep, almost CO2-pure,…...
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TL;DR: In this paper, an extensive dataset on major elements and volatiles (CO2, H2O, S and Cl) in olivine-hosted melt inclusions and embayments from pyroclasts emplaced during explosive eruptions of variable magnitude is presented.
Abstract: Stromboli is known for its persistent degassing and rhythmic strombolian activity occasionally punctuated by paroxysmal eruptions. The basaltic pumice and scoria emitted during paroxysms and strombolian activity, respectively, differ in their textures, crystal contents and glass matrix compositions, which testify to distinct conditions of crystallization, degassing and magma ascent. We present here an extensive dataset on major elements and volatiles (CO2, H2O, S and Cl) in olivine-hosted melt inclusions and embayments from pyroclasts emplaced during explosive eruptions of variable magnitude. Magma saturation pressures were assessed from the dissolved amounts of H2 Oa nd CO2 taking into account the melt composition evolution. Both pressures and melt inclusion compositions indicate that (1) Ca-basaltic melts entrapped in high-Mg olivines (Fo89^90) generate Stromboli basalts through crystal fractionation, and (2) the Stromboli plumbing system can be imaged as a succession of magma ponding zones connected by dikes. The 7^10 km interval, where magmas are stored and differentiate, is periodically recharged by new magma batches, possibly ranging from Ca-basalts to basalts, with a CO2-rich gas phase.These deep recharges promote the formation of bubbly basalt blobs, which are able to intrude the shallow plumbing system (2^4 km), where CO2 gas fluxing enhances H2O loss, crystallization and generation of crystal-rich, dense, degassed magma. Chlorine partitioning into the H2O^CO2-bearing gas phase accounts for its efficient degassing (� 69%) under the open-system conditions of strombolian activity. Paroxysms, however, are generated through predominantly closed-system ascent of basaltic magma batches from the deep storage zone. In this situation crystallization is negligible and sulfur exsolution starts at � 170 MPa. Chlorine remains dissolved in the melt until lower pressures, only 16% being lost upon eruption. Finally, we propose a continuum in explosive eruption energy, from strombolian activity to large paroxysmal events, ultimately controlled by variable pressurization of the deep feeding system associated with magma and gas recharges.
206 citations