Melt inclusion record of the conditions of ascent, degassing, and extrusion of volatile‐rich alkali basalt during the powerful 2002 flank eruption of Mount Etna (Italy)

Spilliaert, N.; Allard, P.; Métrich, Nicole; Sobolev, Alexander V.

doi:10.1029/2005jb003934

Cited by 291 publications

(327 citation statements)

References 71 publications

(126 reference statements)

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“…This indicates pre-eruptive storage at 40 MPa (~1.5 km of lithostatic pressure). The presence of a significant mass of exsolved volatiles, presumably derived either from volatile exsolution within a deeper part of the volcanic system or by vapor/fluid accumulation via closed system exsolution in crustal chambers, is often proposed to play a significant role in basaltic eruptions (Allard et al, 2005;La Spina et al, 2015;Spilliaert et al, 2006;Vergniolle and Jaupart, 1986). Geochemical evidence for this can theoretically be found in melt inclusions (e.g.…”

Section: Decompression Model Resultsmentioning

confidence: 99%

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

et al. 2016

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The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behaviour. In this study we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawai'i. Incomplete exsolution of H 2 O, CO 2 and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modelled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s -1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 minutes from depths of ~2 to ~4 km respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied this varies from 0.1-3.2 wt%, but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather they suggest that for these eruptions decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

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Section: Decompression Model Resultsmentioning

confidence: 99%

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

et al. 2016

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“…It is thought that the separation of gas from melt plays an important role in influencing both the compositions of volcanic aerosol and of the residual melts (e.g. Aiuppa et al, 2004;Spilliaert et al, 2006). Other studies have focused on Etna's influence on metals in groundwater (e.g., Giammanco et al, 1998;Aiuppa et al, 2000), rainwater (e.g., Aiuppa et al, 2006), and biological systems (e.g., Barghigiani et al, 1988;Notcutt and Davies, 1989;Monna et al, 1999;Watt et al, 2007;Martin et al, 2009a;Quayle et al, 2010).…”

Section: Mt Etna (Sicily)mentioning

confidence: 99%

Rapid oxidation of mercury (Hg) at volcanic vents: Insights from high temperature thermodynamic models of Mt Etna's emissions

et al. 2011

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A major uncertainty regarding the environmental impacts of volcanic Hg is the extent to which Hg is deposited locally or transported globally. An important control on dispersion and deposition is the oxidation state of Hg compounds: Hg(0) is an inert, insoluble gas, while Hg(II) occurs as reactive gases or in particles, which deposit rapidly and proximally, near the volcanic vent. Using a new high temperature thermodynamic model, we show that although Hg in Etna's magmatic gases is almost entirely Hg(0) (i.e., gaseous elemental mercury), significant quantities of Hg(II) are likely formed at Etna's vents as gaseous HgCl 2 , when magmatic gases are cooled and oxidised by atmospheric gases. These results contrast with an earlier model study and allow us to explain recent measurements of Hg speciation at the crater rim of Etna without invoking rapid (b 1 min) low temperature oxidation processes. We further model Hg speciation for a series of additional magmatic gas compositions. Compared to Etna, Hg(II) production (i.e., Hg(II)/Hg tot ) is enhanced in more HCl-rich magmatic gases, but is independent of the Hg, HBr and HI content of the magmatic gases. Hg(II) production is not strongly influenced by the initial oxidation state of magmatic gases above NNO, although production is hindered in more reduced magmatic gases. The model and results are widely applicable to other open-vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature Hg speciation in volcanic plumes.

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“…(i) first, de-hydration of a magma can be caused by fluxing with deep-rising CO 2 -rich gas (Spilliaert et al, 2006), a fact which is suggestive of the presence of a magma ponding zone at 2-4 km bsv, where CO 2 -rich gas bubbles accumulate to contents N5 wt. % (Métrich et al, 2010).…”

Section: Melt Inclusion Record Of Magma Ascent and Degassingmentioning

confidence: 99%

A model of degassing for Stromboli volcano

Aiuppa¹,

Bertagnini²,

Métrich³

et al. 2010

Earth and Planetary Science Letters

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153

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A better understanding of degassing processes at open-vent basaltic volcanoes requires collection of new datasets of H 2 O-CO 2 -SO 2 volcanic gas plume compositions, which acquisition has long been hampered by technical limitations. Here, we use the MultiGAS technique to provide the best-documented record of gas plume discharges from Stromboli volcano to date. We show that Stromboli's gases are dominated by H 2 O (48-98 mol%; mean, 80%), and by CO 2 (2-50 mol%; mean, 17%) and SO 2 (0.2-14 mol%; mean, 3%). The significant temporal variability in our dataset reflects the dynamic nature of degassing process during Strombolian activity; which we explore by interpreting our gas measurements in tandem with the melt inclusion record of pre-eruptive dissolved volatile abundances, and with the results of an equilibrium saturation model. Comparison between natural (volcanic gas and melt inclusion) and modelled compositions is used to propose a degassing mechanism for Stromboli volcano, which suggests surface gas discharges are mixtures of CO 2 -rich gas bubbles supplied from the deep (N4 km) plumbing system, and gases released from degassing of dissolved volatiles in the magma filling the upper conduits. The proposed mixing mechanism offers a viable and general model to account for composition of gas discharges at all volcanoes for which petrologic evidence of CO 2 fluxing exists. A combined volcanic gas-melt inclusion-modelling approach, as used in this paper, provides key constraints on degassing processes, and should thus be pursued further.

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Melt inclusion record of the conditions of ascent, degassing, and extrusion of volatile‐rich alkali basalt during the powerful 2002 flank eruption of Mount Etna (Italy)

Cited by 291 publications

References 71 publications

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

Rapid oxidation of mercury (Hg) at volcanic vents: Insights from high temperature thermodynamic models of Mt Etna's emissions

A model of degassing for Stromboli volcano

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