Evidence for deep gas loss in open volcanic systems

Collombet, Marielle; Burgisser, Alain; Colombier, Mathieu; Gaunt, Elizabeth

doi:10.1007/s00445-020-01433-0

Cited by 12 publications

(15 citation statements)

References 80 publications

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“…Experimental data suggest that efficient, channelised gas flow may occur at depths of a few kilometres through rhyolite melt containing 5 wt% H 2 O when subject to a shear strain > 8 (Okumura et al 2008). The addition of crystals may substantially reduce the percolation threshold for system-scale connectivity during vesiculation and may promote efficient gas loss from conduits even at low gas fractions (Colombier et al 2020;Collombet et al 2021;deGraffenried et al 2019;Lindoo et al 2017;Fig. 3b).…”

Section: Degassing In the Volcanic Conduitmentioning

confidence: 99%

Open-vent volcanoes fuelled by depth-integrated magma degassing

2022

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Open-vent, persistently degassing volcanoes—such as Stromboli and Etna (Italy), Villarrica (Chile), Bagana and Manam (Papua New Guinea), Fuego and Pacaya (Guatemala) volcanoes—produce high gas fluxes and infrequent violent strombolian or ‘paroxysmal’ eruptions that erupt very little magma. Here we draw on examples of open-vent volcanic systems to highlight the principal characteristics of their degassing regimes and develop a generic model to explain open-vent degassing in both high and low viscosity magmas and across a range of tectonic settings. Importantly, gas fluxes from open-vent volcanoes are far higher than can be supplied by erupting magma and independent migration of exsolved volatiles is integral to the dynamics of such systems. The composition of volcanic gases emitted from open-vent volcanoes is consistent with its derivation from magma stored over a range of crustal depths that in general requires contributions from both magma decompression (magma ascent and/or convection) and iso- and polybaric second boiling processes. Prolonged crystallisation of water-rich basalts in crustal reservoirs produces a segregated exsolved hydrous volatile phase that may flux through overlying shallow magma reservoirs, modulating heat flux and generating overpressure in the shallow conduit. Small fraction water-rich melts generated in the lower and mid-crust may play an important role in advecting volatiles to subvolcanic reservoirs. Excessive gas fluxes at the surface are linked to extensive intrusive magmatic activity and endogenous crustal growth, aided in many cases by extensional tectonics in the crust, which may control the longevity and activity of open-vent volcanoes. There is emerging abundant geophysical evidence for the existence of a segregated exsolved magmatic volatile phase in magma storage regions in the crust. Here we provide a conceptual picture of gas-dominated volcanoes driven by magmatic intrusion and degassing throughout the crust.

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Section: Degassing In the Volcanic Conduitmentioning

confidence: 99%

Open-vent volcanoes fuelled by depth-integrated magma degassing

2022

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“…In addition to their rheological effect discussed above, crystals strongly affect degassing processes such as bubble nucleation and coalescence and thereby influence permeability development. The effect of crystals is complex and includes several processes that together may reduce the percolation threshold and enhance outgassing at low porosity and possibly deep in the conduit, including bubble deformation (Shields et al 2014;Oppenheimer et al 2015;Lindoo et al 2017), channelling and gas migration (Oppenheimer et al 2015;Parmigiani et al 2017;Collombet et al 2021), brittle-viscous coalescence (Colombier et al 2020), porosity redistribution via strain-localization (Laumonier et al 2011;deGraffenried et al 2019), heterogenous bubble nucleation and an increase in the bubble number density (Hurwitz and Navon 1994;Burgisser et al 2017Burgisser et al , 2020Cáceres et al 2020), and simply enhanced bubble coalescence (Blower, 2001;Cáceres et al 2022).…”

Section: Effect Of Crystals On Degassing In the Dacitic Magmamentioning

confidence: 99%

“…This implies either that (i) heterogenous nucleation initiated early around these phenocrysts in the conduit (Gardner and Denis, 2004), allowing for more time for growth and coalescence or (ii) nucleation occurred in a single and/or continuous event but growth and coalescence were favoured around crystal phases (Cáceres et al 2022). Irrespective of these two hypotheses, crystals likely promote early development of system-spanning coalescence in the conduit of Guagua Pichincha and possibly deep outgassing via a range of processes (Collombet et al 2021).…”

Section: Pore Connectivity and Percolation Modelsmentioning

confidence: 99%

“…However, these pumice clasts measured for permeability correspond to coarse lapilli (> 32 mm in diameter) or bombs and therefore likely experienced some post-fragmentation vesiculation (Mitchell et al 2018;Trafton and Giachetti, 2021). In addition, final porosities observed in vesicular clasts generally do not reflect pre-explosive (lower) porosities of magma in the conduit (Burgisser et al 2019;Collombet et al 2021).…”

Section: The Evolution Of Permeability In the Vesicular Magmamentioning

confidence: 99%

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Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador

et al. 2022

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Stratovolcanoes are commonly characterised by cyclic eruptive activity marked by transitions between dome-forming, Vulcanian, Subplinian and Plinian eruptions. Guagua Pichincha volcano (Ecuador) has been a location of such cyclicity for the past ~ 2000 years, with Plinian eruptions in the first and tenth centuries AD (Anno Domini/after Christ), and CE (Common Era) 1660, which were separated by dome-forming to Subplinian eruptions, such as the recent 1999–2001 eruption. These cycles are therefore a prominent example of effusive-explosive transitions at varying timescales. Here, we investigate the reasons for such shifts in activity by focusing on degassing and outgassing processes within the conduit. We have coupled a petrophysical and textural analysis of dacites from the CE 1660 Plinian eruption and the 1999–2001 dome-forming/Vulcanian eruption, with different percolation models in order to better understand the role of degassing on eruptive style. We demonstrate that the transition from dome-forming to Plinian activity is correlated with differences in phenocryst content and consequently in bulk viscosity. A lower initial phenocryst content and viscosity is inferred for the Plinian case, which promotes faster ascent, closed-system degassing, fragmentation and explosive activity. In contrast, dome-forming phases are promoted by a higher magma viscosity due to higher phenocryst content, with slower ascent enhancing gas escape and microlite crystallization, decreasing explosivity and yielding effusive activity. Resumen Los estratovolcanes se caracterizan comúnmente por presentar actividad eruptiva cíclica, marcada por transiciones entre erupciones formadoras de domos y erupciones de tipo Vulcanianas, Subplinianas y Plinianas. El volcán Guagua Pichincha (Ecuador) ha dado lugar a tal ciclicidad durante los últimos ~ 2000 años, con erupciones Plinianas tanto en los siglos Primero y Décimo, como en el año 1660, las cuales estuvieron intercaladas por erupciones formadoras de domos y de tipo Subplinianas, tal como ocurrió durante la erupción reciente de 1999–2001. Estos ciclos son, por lo tanto, ejemplos destacados de transiciones eruptivas de tipo efusiva-explosiva a escalas de tiempo variadas. En este trabajo, investigamos las razones de tales cambios de actividad enfocándonos en procesos de exsolución y pérdida de gases del magma en el conducto (desgasificación en sistemas cerrado y abierto). Hemos acoplado análisis petrofísicos y texturales tanto de dacitas de la erupción Pliniana de 1660, como de la erupción formadora de domos/Vulcaniana de 1999–2001, junto con diferentes modelos de percolación, para así comprender mejor el rol de la exsolución de volátiles en el estilo eruptivo. Demostramos que la transición desde una actividad efusiva formadora de domos a una Pliniana está correlacionada con diferencias en el contenido de fenocristales y, subsecuentemente, con la viscosidad total del magma. Un contenido inicial menor de fenocristales y una menor viscosidad se infiere para el caso Pliniano, lo que promueve un ascenso más rápido, desgasificación en sistema cerrado, fragmentación y finalmente actividad explosiva. Por el contrario, las fases formadoras de domos son promovidas por una viscosidad mayor debido a un contenido mayor de fenocristales, con ascenso más lento promoviendo a su vez el escape de gases y la cristalización de microlitos, disminuyendo la explosividad y produciendo actividad efusiva.

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“…Petrological analysis of melt inclusions and modeling support this possibility, and such fluid addition from depth can also account for the permanent volcanic plumes of many mafic volcanoes. Given the dependency of different volatile elements on pressure, the deeper parts of the system are typically CO2-rich, because CO2 is much less soluble than water and SO2 with decreasing pressure, and can thus degas earlier and flux through the upper parts of the system, with mechanisms that may include channeling Collombet et al, 2021;Spilliaert et al, 2006). CO2 fluxing can have widespread effects on a shallow magmatic system that vary depending on the pressure, but include the crystallization of high-Mg, high-Ca pyroxene rims .…”

Section: Fluid Fluxing From Depth and Creation Of An Exsolved Volatile Phasementioning

confidence: 99%

Petrological and monitoring insights into the mechanisms driving eruptions of Kelud volcano, Indonesia

Utami¹

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Our capacity to anticipate volcanic eruptions depends on accurate interpretation of unrest signals coupled with understanding of the magmatic system and processes. This is challenging for most volcanoes, including Kelud (Indonesia), that erupts effusively and explosively. In this thesis, I address some unknowns to this topic by quantitatively determining the magmatic processes, storage conditions, timescales, and ascent rates of three eruptions at Kelud (1990Kelud ( , 2007Kelud ( , 2014. I relate these variables to the time series of monitoring data for the same events. I show that explosive eruptions are likely driven by fluid accumulation and degassing that began months before eruption. I performed experiments to find that magma storage conditions for explosive and effusive eruptions were similar, and I demonstrate that ascent rates and viscosity vary with eruption style. These results can be used to improve volcanic hazard assessment and monitoring through robust petrology-based conceptual frameworks for different eruption styles.

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Evidence for deep gas loss in open volcanic systems

Cited by 12 publications

References 80 publications

Open-vent volcanoes fuelled by depth-integrated magma degassing

Open-vent volcanoes fuelled by depth-integrated magma degassing

Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador

Petrological and monitoring insights into the mechanisms driving eruptions of Kelud volcano, Indonesia

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