Mantle plumes are oxidised

Moussallam, Yves; Longpré, Marc‐Antoine; McCammon, Catherine; Gómez-Ulla, Alejandra; Rose-Koga, Estelle; Scaillet, Bruno; Peters, Nial; Gennaro, Emanuela; Paris, Raphaël; Oppenheimer, Clive

doi:10.1016/j.epsl.2019.115798

Cited by 98 publications

(106 citation statements)

References 89 publications

(148 reference statements)

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“…Considering that Fe 3+ /Fe tot of 0.46 seems rather oxidized, we suggest that an oxygen fugacity of NNO+1.1 provides an upper bound for the phonotephrites. The calculated melt H 2 O contents are above those found in olivine-hosted melt inclusions from Fogo (up to 2.6 wt%; Moussallam et al, 2019), but appear plausible considering the differentiated nature of the phonotephrites compared to the mafic tephras investigated by these authors.…”

Section: Amphibole Thermobarometry and Hygrometrymentioning

confidence: 53%

“…Petrological studies of Fogo provided detailed data for the magma plumbing systems of the 1951, 1995, and 2014-2015 eruptions (Munhá et al, 1997;Hildner et al, 2011Hildner et al, , 2012Mata et al, 2017), thermobarometric data for earlier eruptions (Hildner et al, 2012), and analyses of some melt inclusions (Moussallam et al, 2019). These studies showed that the erupted magmas were stored before eruption within the uppermost mantle between 15 and 30 km depth, and stalled during ascent within the lower crust at 8-13 km depth.…”

Section: Geological Overview Of Fogomentioning

confidence: 99%

“…For comparison, we applied Equations ( 33) and (30) of Putirka (2008) to the same data assuming a H 2 O content of 2.5 wt% based on results for olivine-hosted melt inclusions (Moussallam et al, 2019). By using filter 1, average temperatures are 1135 ± 15 • C for tephrites and 1079 ± 13 • C for phonotephrites; corresponding pressures are 825 ± 115 and 701 ± 145 MPa, respectively (±1 σ indicated).…”

Section: Thermobarometry Of Clinopyroxene Rimsmentioning

confidence: 99%

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Magma Plumbing During the 2014–2015 Eruption of Fogo (Cape Verde Islands)

et al. 2020

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Phenocrysts in volcanic rocks are recorders of magmatic processes that have occurred at depth before and during a volcanic eruption. Our petrological investigations of stratigraphically controlled tephrite and phonotephrite samples from the latest eruption of Fogo (Cape Verde Islands) aimed to reconstructing magma storage and transport. The dates of sample emplacement have been determined using satellite instrumentderived high resolution thermal infrared maps. All samples are strongly phyric and commonly contain complexly zoned clinopyroxene crystals and cumulate fragments. Clinopyroxenes from all samples exhibit 10-50 µm wide rim zones, inferred to have grown in a few days to weeks during the ongoing eruption as a consequence of H 2 O loss from the melt. Clinopyroxene-melt thermobarometry using tephrite groundmass compositions suggests that the rims formed at upper mantle pressures of around 600 MPa (21 km depth). This level is interpreted to reflect temporary reduction in magma ascent velocity by near-isobaric movement through a complex storage system. Previously, the tephrite magma had accumulated at a deeper level, possibly between 700 and 900 MPa as indicated by clinopyroxene cores (Mata et al., 2017). The cause for H 2 O loss initiating rim growth could be degassing after rise of the magma from the deeper level, or CO 2 flushing by a carbonic fluid phase released at depth. Corresponding data from phonotephrites indicate last equilibration at around 440 MPa (16 km); the phonotephrite magma is inferred to be a residuum from an earlier magmatic event that was entrained by advancing tephrite. Microthermometry of CO 2 -dominated fluid inclusions in tephrite clinopyroxenes results in pressures of around 330 MPa (12 km), indicating another short pause in magma ascent in the lowermost crust. Rim zonations of olivine phenocrysts indicate that after leaving this final stalling zone, the magma ascended to the surface in less than half a day. In strong contrast to these petrological equilibration depths, seismic events precursory to the eruption were located at < 5 km below sea level, with only two exceptions at 17 and 21 km depth consistent with our barometry. Our results enhance the understanding of this potentially dangerous volcano, which helps to interpret future pre-eruptive unrest.

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Section: Amphibole Thermobarometry and Hygrometrymentioning

confidence: 53%

Section: Geological Overview Of Fogomentioning

confidence: 99%

Section: Thermobarometry Of Clinopyroxene Rimsmentioning

confidence: 99%

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Magma Plumbing During the 2014–2015 Eruption of Fogo (Cape Verde Islands)

et al. 2020

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“…Such a scenario might occur during graphite-saturated melting (e.g., Eguchi and Dasgupta, 2018b). However, the Fe 3+ /Fe 2+ ratios of basalts and melt inclusions from MORB and ocean islands indicate the mantle is not sufficiently reduced for graphite-present melting to occur ubiquitously (Bézos and Humler, 2005;Cottrell and Kelley, 2011;Shorttle et al, 2015;Berry et al, 2018;Moussallam et al, 2019).…”

Section: A Global Array Controlled By the Melting Process?mentioning

confidence: 99%

The global melt inclusion C/Ba array: mantle variability, melting process, or degassing?

Matthews¹,

Shorttle²,

Maclennan³

et al. 2022

Preprint

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“…In a second session (in 2018), XANES spectra were collected for the 6 experimental glasses and the 11 MIs from FS tephra characterized in this study, along with 3 MIs from (1 MI from 2002/2003, 1 from 2013 and 1 MI from FS eruptions) following the methodology described in Moussallam et al, (2019). The X-rays were focused with Kirkpatrick-Baez mirrors down to 2 µm (horizontal) × 1.2 µm (vertical) beam size.…”

Section: Xanes Fe 3+ /ʃFe Investigationmentioning

confidence: 99%

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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Mantle plumes are oxidised

Cited by 98 publications

References 89 publications

Magma Plumbing During the 2014–2015 Eruption of Fogo (Cape Verde Islands)

Magma Plumbing During the 2014–2015 Eruption of Fogo (Cape Verde Islands)

The global melt inclusion C/Ba array: mantle variability, melting process, or degassing?

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

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