Mantle to surface degassing of carbon- and sulphur-rich alkaline magma at El Hierro, Canary Islands

Longpré, Marc‐Antoine; Stix, John; Klügel, Andreas; Shimizu, Nobumichi

doi:10.1016/j.epsl.2016.11.043

Cited by 66 publications

(92 citation statements)

References 78 publications

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“…2-5 times less than our estimation (3.5 ± 1.4 wt%). Our study fully supports similar recent revaluations of mantle CO 2 like (i) at Kilauea by coupling volcanic CO 2 emission rates with probabilistic magma supply rates (Anderson and Poland, 2017) and, (ii) at El Hierro based on the highest CO 2 contents ever measured in melt inclusions from ocean island volcano (Longpré et al, 2017). Note that at El Hierro, these authors have estimated a primitive dissolved CO 2 content in the range 2.5-5.0 wt% (by extrapolation to undegassed CO 2 /Nb), thus overlapping our estimation for PdF melts (3.5 ± 1.4 wt%).…”

Section: Comparison With Other Ocean Basaltic Volcanoes and Involvemesupporting

confidence: 88%

“…8) might be a classical model for numerous other ocean basaltic volcanoes, where barometric estimations evidence the presence of multiple deep magma ponding zones playing a major role in melt differentiation as e.g. Azores, Cape Verde, Canaries Islands (Zanon and Frezzotti, 2013;Klü gel et al, 2015;Longpré et al, 2017), (2) the low d 13 C signature inferred for mantle reservoirs (À6‰; Loihi, Pitcairn; down to À8‰ in MORB mantle, e.g., Sano and Marty, 1995;Deines, 2002;Aubaud et al, 2004 and references therein) could already reflect an early stage of degassing in the upper mantle rather than a contribution of recycled carbon (Exley et al, 1986;Aubaud et al, 2006), or a mantle heterogeneity.…”

Section: Comparison With Other Ocean Basaltic Volcanoes and Involvemementioning

confidence: 99%

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Extensive CO2 degassing in the upper mantle beneath oceanic basaltic volcanoes: First insights from Piton de la Fournaise volcano (La Réunion Island)

Boudoire

Rizzo

Muro

et al. 2018

Geochimica et Cosmochimica Acta

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In spite of its major role on the atmospheric volatile budget, climate, and tracking magmatic transfers, mantle (CO 2 ) degassing below volcanoes is still poorly understood. Most of the studies on this scientific topic lack constraint on the CO 2 concentration of primary melts, the depth at which it starts degassing, and the extent of this process in the mantle. In this study of Piton de la Fournaise (PdF) volcano, we couple geochemistry of low solubility gases (He, Ar, CO 2 , d 13 C) in fluid inclusions (FIs) and petro-chemistry of magmatic inclusions on a set of olivine and clinopyroxene crystals from basalts and ultramafic enclaves.We constrain basaltic melt degassing at PdF over a large pressure range (from 4 GPa up to the surface). Based on CO 2 -He-Ar systematics, we infer that extensive degassing occurs already in the upper mantle (4-1 GPa) and it is favored by multiple steps of magma ponding and differentiation up to the mantle-crust underplating depth (0.4 GPa). Thus, we calculate that basaltic melts injected at crustal depth (<0.4 GPa) have already exsolved $94 ± 5 wt% of their primary CO 2 content in accordance with (1) the evolved and degassed signature of erupted lavas and (2) the weakness of inter-eruptive gas emissions in the active area bearing low-temperature vapor-dominated fumaroles. Our results at PdF strongly contrast with previous findings on other ocean island volcanoes having a higher magma production rate and faster magma ascent, like Kilauea (Hawaii), whose basalts experience only limited extent of differentiation and degassing. We propose that extensive degassing already in the upper mantle can be a common process for many volcanoes of the Earth and is tightly dependent on the dynamics of magma ascent and differentiation across multiple ponding zones.Based on the modeling developed in this study, we propose a new estimation of the CO 2 content (up to 3.5 ± 1.4 wt%) in primary basaltic melts at PdF leading to a carbon content in the mantle source of 716 ± 525 ppm. This new estimation is considerably higher than the few previous calculations performed for Ocean Island Basalts (OIB) systems. Another implication of this work involves the possible bias between the d 13 C measured in volcanic gas emissions (<À6‰) and that of primary vapour phase (À0.5 ± 0.5‰) constrained in this work. This bias would confirm the early step of extensive CO 2 degassing within the upper mantle and could represent an alternative for the hypotheses of carbon recycling or mantle heterogeneity in support of the low d 13 C signature of some mantle reservoirs. This study bears significant implications on the global budget of volcanic ⇑ Corresponding author at: Observatoire Volcanologique du Piton de la Fournaise ((G. Boudoire). volatile emissions, chiefly regarding the contribution of past and future emissions of volcanic CO 2 to climate dynamics, and on volcanic gas monitoring.

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Section: Comparison With Other Ocean Basaltic Volcanoes and Involvemesupporting

confidence: 88%

Section: Comparison With Other Ocean Basaltic Volcanoes and Involvemementioning

confidence: 99%

Extensive CO2 degassing in the upper mantle beneath oceanic basaltic volcanoes: First insights from Piton de la Fournaise volcano (La Réunion Island)

Boudoire

Rizzo

Muro

et al. 2018

Geochimica et Cosmochimica Acta

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“…10), and, therefore, not suitable for the calculation of saturation pressures. However, we note that the high values of incompatible elements (particularly Nb and Ba), and correspondingly low values of CO 2 /Nb and CO 2 /Ba, are at odds with studies on other volatile-undersaturated basaltic samples (Hudgins et al 2015;Le Voyer et al 2017;Longpré et al 2017;Rosenthal et al 2015). We make two comments about this.…”

Section: Volatile-trace Element Systematicsmentioning

confidence: 46%

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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“…The clear-cut variation of the chemistry of Type II inclusions, which consist of pure CO2, suggests a different fluid origin, probably by degassing of magmas. Canary alkaline mafic magmas are carbon-rich and thus can begin to exsolve CO2-rich fluids at great pressures (> 1 GPa; Longpré et al 2017) in the oceanic lithospheric mantle.…”

Section: Discussionmentioning

confidence: 99%

Lithospheric magma dynamics beneath the El Hierro Volcano, Canary Islands: insights from fluid inclusions

et al. 2017

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In active volcanoes, petrological studies have been proven to represent a reliable approach to defining the depth conditions of magma transport and storage in the mantle and the crust. Based on fluid inclusion mineral geothermobarometry in mantle xenoliths, we propose a model for the recent magma plumbing system of the Island of El Hierro (Canary Islands). Studied peridotites are entrained in a lava flow from El Yulan Valley, which is part of the Rift volcanism activity at approximately 40-30 ka. Peridotites are spinel lherzolites, harzburgites and dunites equilibrated in the shallow mantle at pressures from 1.5 to 2 GPa. 800 to 950°C (LT peridotites). Manuscript Click here to download Manuscript Oglialoro et al revised.docx Click here to view linked References 2 and higher equilibration temperatures from 900 to 1100°C (HT peridotites). Microthermometry and Raman analyses of fluid inclusions show trapping of two distinct fluid phases: early Type I metasomatic CO2-N2 fluids (d = 1.19 g/cm 3), coexisting with silicate-carbonate melts, in LT peridotites; and late Type II pure CO2 fluids (d = 0.99 to 1.11 and 0.65-0.75 g/cm 3) in both LT and HT peridotites. Type I fluids represent metasomatic phases in the deep oceanic lithosphere (60-65 km) before the onset of magmatic activity, whereas Type II CO2 fluids testify for fluid trapping episodes during the ascent of xenoliths in host mafic magmas. Identification of magma accumulation zones through interpretation of Type II CO2 fluid inclusions and mineral geothermobarometry indicate the presence of a vertically stacked system of interconnected small magma reservoirs in the shallow lithospheric mantle from 22 to 36 km depth (or 0.67 to 1 GPa). This deeper magma accumulation region fed a short-lived magma storage region located in the lower oceanic crust at 10-12 km depth (or 0.26-0.34 GPa). According to our model, the 40-30 ka old volcanic activity of El Hierro is related to mantle magma dynamics, as also proposed for the 2011-2012 eruption. developed on the margin of the African Plate (Fig. 1a) (Robertson and Stillman 1979;

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Mantle to surface degassing of carbon- and sulphur-rich alkaline magma at El Hierro, Canary Islands

Cited by 66 publications

References 78 publications

Extensive CO2 degassing in the upper mantle beneath oceanic basaltic volcanoes: First insights from Piton de la Fournaise volcano (La Réunion Island)

Extensive CO2 degassing in the upper mantle beneath oceanic basaltic volcanoes: First insights from Piton de la Fournaise volcano (La Réunion Island)

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Lithospheric magma dynamics beneath the El Hierro Volcano, Canary Islands: insights from fluid inclusions

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