Melt inclusions track melt evolution and degassing of Etnean magmas in the last 15 ka

Gennaro, Emanuela; Iacono-Marziano, Giada; Paonita, Antonio; Rotolo, Silvio G.; Martel, Caroline; Rizzo, Andrea Luca; Pichavant, Michel; Liotta, Marcello

doi:10.1016/j.lithos.2018.11.023

Cited by 23 publications

(49 citation statements)

References 88 publications

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“…FS tephra spreads mostly in the east and north flanks of the Etnean volcano, reaching a maximum thickness of 110 cm 7 km away from the summit craters. This rock (phenocrysts ≤10 vol%) has a picro-basaltic composition (MgO =17 wt%, Gennaro et al, 2019), and contains euhedral Fo 89-91 olivine (up to ~ 5 mm in size), subhedral clinopyroxene and rare Crspinel, as microphenocrysts and/or included in olivine (e.g., Correale et al, 2014;Corsaro and Métrich, 2016;Gennaro et al, 2019;Kamenetsky et al, 2007).…”

Section: Etnean Melt Inclusionsmentioning

confidence: 99%

“…The MIs from FS products have already been characterized for their chemical compositions and volatile contents (Corsaro and Métrich, 2016;Gennaro et al, 2019;Kamenetsky et al, 2007). They are highly primitive (up to 12 wt% MgO) and show particularly high volatile contents, with H 2 O up to 6 wt.%, CO 2 up to > 5000 ppm, S up to 3550 ppm, and Cl up to > 3000 ppm.…”

Section: Etnean Melt Inclusionsmentioning

confidence: 99%

“…They are highly primitive (up to 12 wt% MgO) and show particularly high volatile contents, with H 2 O up to 6 wt.%, CO 2 up to > 5000 ppm, S up to 3550 ppm, and Cl up to > 3000 ppm. Entrapment depths calculated from H 2 O and CO 2 contents range between 2 and 16 km bsl (Gennaro et al, 2019) indicating that FS MIs are probably the most representative samples of the redox state of deep and primitive magmas.…”

Section: Etnean Melt Inclusionsmentioning

confidence: 99%

“…Extremely debated is also the geochemical variability (e.g., increase of alkali, mainly K 2 O, and radiogenic elements) in the recent Etnean magmas, as observed from isotopic and elemental geochemical data on rocks and melt inclusions (e.g., Correale et al, 2014;Corsaro and Métrich, 2016;Di Renzo et al, 2019;Gennaro et al, 2019;Schiavi et al, 2015;and references therein). For example, the post-1971 enrichment in alkalis (K, Rb, Cs) and radiogenic Sr and B elements (e.g., Allard et al, 2006;Armienti et al, 2004;Ferlito and Lanzafame, 2010;Métrich et al, 2004) has been ascribed alternatively to (i) the interaction between an OIB-type (or HIMU-type) mantle source and an enriched component (EM1), corresponding to a slab-modified mantle or to (ii) the mixing between mantle-derived magmas and a K-and Si-enriched melt (Schiano and Clocchiatti, 1994).…”

Section: Introductionmentioning

confidence: 99%

“…For example, the post-1971 enrichment in alkalis (K, Rb, Cs) and radiogenic Sr and B elements (e.g., Allard et al, 2006;Armienti et al, 2004;Ferlito and Lanzafame, 2010;Métrich et al, 2004) has been ascribed alternatively to (i) the interaction between an OIB-type (or HIMU-type) mantle source and an enriched component (EM1), corresponding to a slab-modified mantle or to (ii) the mixing between mantle-derived magmas and a K-and Si-enriched melt (Schiano and Clocchiatti, 1994). On the other hand, Gennaro et al (2019) proposed that part of the variability of major elements and volatiles observed in the Etnean magmas of the last 15 ka could be ascribed to differentiation processes of a primitive FS-type magma, occasionally accompanied by secondary source-related and/or crustal processes.…”

Section: Introductionmentioning

confidence: 99%

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Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Gennaro

Paonita

Iacono-Marziano

et al. 2020

Journal of Petrology

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Sulphur behaviour and variations in redox conditions during magma differentiation and degassing in Mt. Etna (Italy) volcanic system have been explored by integrating the study of olivine-hosted melt inclusions (MIs) with an experimental survey of sulphur solubility in hydrous basaltic magmas. Sulphur solubility experiments were performed at conditions relevant to the Etnean plumbing system (1200 °C, 200 MPa and oxygen fugacity between NNO + 0.2 and NNO + 1.7, with NNO being the Nickel-Nickel Oxide buffer), and their results confirm the important control of oxygen fugacity (fO2) on S abundance in mafic magmas and on S partitioning between fluid and melt phases (DSfluid/melt). The observed DSfluid/melt value increases from 51 ± 4 to 146 ± 6 when fO2 decreases from NNO + 1.7 ± 0.5 to NNO + 0.3. Based on the calculated DSfluid/melt and a careful selection of previously published data, an empirical model is proposed for basaltic magmas in order to predict the variation of DSfluid/melt values upon variations in P (25–300 MPa), T (1030–1200 °C) and fO2 (between NNO-0.8 and NNO + 2.4). Olivine-hosted melt inclusions (Fo89-91) from tephra of the prehistoric (4 ka BP) sub-plinian picritic eruption, named FS (“Fall Stratified”), have been investigated for their major element compositions, volatile contents and iron speciation (expressed as Fe3+/ƩFe ratio). These primitive MIs present S content from 235 ± 77 to 3445 ± 168 ppm, while oxygen fugacity values, estimated from Fe3+/ƩFe ratios, range from NNO + 0.7 ± 0.2 to NNO + 1.6 ± 0.2. Iron speciation has also been investigated in more evolved and volatile-poorer Etnean MIs. The only primitive melt inclusion from Mt. Spagnolo eruption (4–15 ka BP) presents a S content of 1515 ± 49 ppm and an estimated fO2 of NNO + 1.4 ± 0.1. The more evolved MIs (from 2002/2003, 2006, 2008/2009 and 2013 eruptions) have S content lower than 500 ppm, and their Fe3+/ΣFe ratios result in fO2 between NNO-0.9 ± 0.1 and NNO + 0.4 ± 0.1. Redox conditions and S behaviour in Etnean magmas during degassing and fractional crystallization were modelled coupling MELTS code with our empirical DSfluid/melt model. Starting from a FS-type magma composition and upon decrease of T and P, fractional crystallization of olivine, clinopyroxene, spinel and plagioclase causes a significant fO2 decrease. The fO2 reduction, in turn, causes a decrease in sulphur solubility and an increase in DSfluid/melt, promoting S exsolution during magma ascent, which further enhances the reduction of fO2. For the evolved melt inclusions of 2002–2013 eruptions, magma differentiation may therefore have played a crucial role in decreasing redox conditions and favouring efficient S degassing. Differently, during the unusual FS eruption, only limited melt evolution is observed and S exsolution seems to have been triggered by a major pressure decrease accompanied by H2O and CO2 exsolution during fast magmatic ascent.

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Section: Etnean Melt Inclusionsmentioning

confidence: 99%

Section: Etnean Melt Inclusionsmentioning

confidence: 99%

Section: Etnean Melt Inclusionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Gennaro

Paonita

Iacono-Marziano

et al. 2020

Journal of Petrology

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Thermo-barometric constraints on the Mt. Etna 2015 eruptive event

Giacomoni

Casetta

Valenti

et al. 2021

Contrib Mineral Petrol

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The petrological study of volcanic products emitted during the paroxysmal events of December 2015 from the summit craters of Mount Etna allow us to constrain T-P-XH2O phase stability, crystallization conditions, and mixing processes along the main open-conduit feeding system. In this study, we discuss new geochemical, thermo-barometric data and related Rhyolite-MELTS modelling of the eruptive activity that involved the concomitant activation of all summit craters. The results, in comparison with the previous paroxysmal events of the 2011–2012, reinforce the model of a vertically extended feeding system and highlight that the activity at the New South-East Crater was fed by magma residing at a significantly shallower depth with respect to the Central Craters (CC) and North-East Crater (NEC), even if all conduits were fed by a common deep (P = 530–440 MPa) basic magmatic input. Plagioclase dissolution, resorption textures, and the Rhyolite-MELTS stability model corroborate its dependence on H2O content; thus, suggesting that further studies on the effect that flushing from fluids with different H2O/CO2 ratio are needed to understand the eruption-triggering mechanisms for high energetic strombolian paroxysmal episodes.

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Geochemistry and volatile contents of olivine-hosted melt inclusions from Mt. Etna tholeiitic and alkaline magmatism

Giacomoni,

Masotta,

Delpech

et al. 2024

Contrib Mineral Petrol

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The analysis of olivine-hosted melt inclusions (MIs) from the whole sub-alkaline and alkaline magmatic suites of Mt. Etna provides fundamental information about the composition of undifferentiated magmas and their pristine volatile content. Olivine crystals (Fo88-66) were selected for Secondary Ion Mass Spectrometry (SIMS) analysis of volatile species (H2O, CO2, F, Cl and S) contained in their host MIs, after preliminary high-pressure/high-temperature re-homogenization, which allowed to reduce the developing of cracks in the host olivine and diffusion-driven outgassing of volatiles from the melt inclusions. This permitted to explore the compositional variability of volatiles of undifferentiated melts and the degassing behavior through the feeding system. The studied MIs show significant major elements compositional heterogeneities (44.57–52.37 wt% SiO2; 3.60–7.51 wt% Na2O + K2O). Fractionation modelling was performed with Rhyolite-MELTs under variable fO2 regimes (∆FMQ + 1.5 to + 3), starting from the less evolved MIs compositions and ultimately reproducing most of the observed compositional trends. Mantle melting modelling was used to replicate the observed MIs composition, starting from a spinel-lherzolitic source, accounting for the alkalinity and Fe content of reproduced melts by varying the eutectic contribution of Amph/Phlog and Opx/Cpx respectively. Although most of the studied MIs were degassed in an open-conduit regime, the observed range of volatile concentration in MIs (2.42–6.14 wt% H2O; 308–8474 ppm CO2; 132–697 ppm F; 221–1766 ppm Cl and 16–1992 ppm S) is correlated with a slight decrease in the molar H2O/(H2O + CO2) ratio from early tholeiites to the recent 2015 alkaline products. This observation allows to estimate a minimum 12,250 ppm CO2 and a maximum of 6.14 wt% H2O in primary melts of the current activity.

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Melt inclusions track melt evolution and degassing of Etnean magmas in the last 15 ka

Abstract: We present major elements compositions and volatiles contents of olivine-hosted melt inclusions from Etna volcano (Italy), which extend the existing database with the aim of interpreting the chemical variability of Etnean magmas over the last 15 ka. Olivine phenocrysts were selected from

Cited by 23 publications

References 88 publications

Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Thermo-barometric constraints on the Mt. Etna 2015 eruptive event

Geochemistry and volatile contents of olivine-hosted melt inclusions from Mt. Etna tholeiitic and alkaline magmatism

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