Outgassing through magmatic fractures enables effusive eruption of silicic magma

Crozier, Josh; Tramontano, Samantha; Forte, Pablo; Oliva, S. J. C.; Gonnermann, H. M.; Lev, Einat; Manga, M.; Myers, M.; Rader, Erika; Ruprecht, Philipp; Tuffen, Hugh; Paisley, Rebecca; Houghton, B. F.; Shea, Thomas; Schipper, C. Ian; Castro, Jonathan M.

doi:10.1016/j.jvolgeores.2022.107617

Cited by 9 publications

(5 citation statements)

References 91 publications

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“…In contrast, we attribute the present permeability values to primary percolation (linked to direct coalescence processes) and not to posterior percolation resulting of buoyancy, deformation, or fracturing. It could even imply that the gas channels we observed are preferential sites for subsequent fracturing (Crozier et al., 2022). Here we show that those permeability values are also consistent with a deep conduit location at rest, that is, coalescence and channeling related percolation.…”

Section: Conclusion: Implication For Volcanic Outgassingmentioning

confidence: 89%

Experimental Evidence of Primary Permeability at Very Low Gas Content in Crystal‐Rich Silicic Magma

Theurel,

Collombet,

Burgisser

et al. 2024

Geophysical Research Letters

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Eruptive dynamics is influenced by gas escape from the ascending magma. Gas pathways form in the magma via bubble coalescence, leading to gas channeling. Magmatic crystals play a key role in gas channel formation. This work constrains experimentally decompression‐induced coalescence in high‐crystallinity silicic magmas without external deformation, focusing on low gas content and bimodal crystal size (microlites and phenocrysts). All percolating samples have permeabilities of 10−14 m2 at bulk porosities of 7–10 vol% and bulk crystallinities up to 75 vol%. Our results demonstrate the possibility of coalescence‐related outgassing at high pressure (120–350 MPa) and without external strain, which corresponds to magma stagnating deep in a volcanic conduit. Channeling at such low gas content implies that bimodal crystallinity favors effusive over explosive volcanic behavior. It may also be the missing physical mechanism explaining gas transfer across magmatic systems despite high melt viscosity and low or absent magma extrusion.

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Section: Conclusion: Implication For Volcanic Outgassingmentioning

confidence: 89%

Experimental Evidence of Primary Permeability at Very Low Gas Content in Crystal‐Rich Silicic Magma

Theurel,

Collombet,

Burgisser

et al. 2024

Geophysical Research Letters

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“…Such small initial porosity is much lower than that predicted by equilibrium (Collombet et al., 2021) at the depth estimated for these breadcrust bombs (10–20 MPa equivalent to ∼400–800 m using a conduit density of 2,500 kg/m³; Wright et al., 2007), implying some outgassing process that reduced the porosity by gas escape and pore collapse during ascent and/or stalling at shallow levels in the plug. Several studies have shown that outgassing in crystal‐rich magmas can occur deep in the conduit via channeling (e.g., Collombet et al., 2021; Crozier et al., 2022; Parmigiani et al., 2017). Initial (vesicle‐free) phenocryst content in the breadcrust bombs is 40.1–41.5 vol% (Wright et al., 2023), which corresponds to the lower bound of the range favorable for channeling (40–70 vol%; Parmigiani et al., 2017).…”

Section: Discussionmentioning

confidence: 99%

Pre‐Eruptive Outgassing and Pressurization, and Post‐Fragmentation Bubble Nucleation, Recorded by Vesicles in Breadcrust Bombs From Vulcanian Activity at Guagua Pichincha Volcano, Ecuador

Colombier,

Manga,

Wright

et al. 2023

JGR Solid Earth

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Breadcrust bombs formed during Vulcanian eruptions are assumed to originate from the shallow plug or dome. Their rim to core texture reflects the competition between cooling and degassing timescales, which results in a dense crust with isolated vesicles contrasting with a highly vesicular vesicle network in the interior. Due to relatively fast quenching, the crust can shed light on pre‐ and syn‐eruptive conditions prior to or during fragmentation, whereas the interior allows us to explore post‐fragmentation vesiculation. Investigation of pre‐ to post‐fragmentation processes in breadcrust bombs from the 1999 Vulcanian activity at Guagua Pichincha, Ecuador, via 2D and 3D textural analysis reveals a complex vesiculation history, with multiple, spatially localized nucleation and growth events. Large vesicles (Type 1), present in low number density in the crust, are interpreted as pre‐eruptive bubbles formed by outgassing and collapse of a permeable bubble network during ascent or stalling in the plug. Halos of small, syn‐fragmentation vesicles (Type 2), distributed about large vesicles, are formed by pressurization and enrichment of volatiles in these haloes. The nature of the pressurization process in the plug is discussed in light of seismicity and ground deformation signals, and previous textural and chemical studies. A third population (Type 3) of post‐fragmentation small vesicles appears in the interior of the bomb, and growth and coalescence of Type 2 and 3 vesicles causes the transition from isolated to interconnected bubble network in the interior. We model the evolution of viscosity, bubble growth rate, diffusion timescales, bubble radius and porosity during fragmentation and cooling. These models reveal that thermal quenching dominates in the crust whereas the interior undergoes a viscosity quench caused by degassing, and that the transition from crust to interior corresponds to the onset of percolation and development of permeability in the bubble network.

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“…Recent numerical modeling by Crozier et al (2022) has established the importance of magma fracturing to sustaining non-violent effusive behavior and influencing explosive-effusive transitions.…”

Section: Magma Deformation In Response To Gas Expansionmentioning

confidence: 99%

“…Coalescence of microcracks into macroscopic fractures could lead to a system-spanning connected network that would enhance outgassing (Heap et al 2014a(Heap et al , 2015a. Bubble networks and permeable wall rocks are probably not permeable enough to cause effusive eruptions of low porosity silicic lavas, emphasizing the importance that outgassing through magma fracturing may have (Crozier et al 2022). Moreover, because fracturing can facilitate outgassing in crystal-rich systems, which our experiments imply can occur at 𝜙 ≤ 0.1, the concept of a bubble percolation threshold appears to be of limited utility in crystal-rich magmas.…”

Section: Critical Porosity and Permeabilitymentioning

confidence: 99%

Release the crackin': The influence of brittle behavior on gas retention in crystal-rich magma

Herbst,

Whittington,

Pistone

et al. 2024

Bull Volcanol

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Crystal-rich silicic lavas commonly erupt from hazardous lava dome-forming volcanoes, characterized by both effusive and explosive eruptions. Magma explosivity is inherently dependent on its ability to store pressurized gas, which can be released through permeable pathways like fractures or connected bubbles, yet the role crystals play in regulating gas escape is poorly constrained in crystal-rich systems. We explored the gas storage capacity and outgassing efficiency of crystalrich magmas through experimental vesiculation of hydrous dacite samples containing crystal volume fractions (𝜙 𝑥 ) between 0.5 and 0.8. The maximum unconnected gas volume (isolated porosity) decreases exponentially with increasing crystallinity. We quantify the relative outgassing efficiency as a function of 𝜙 𝑥 using changes in isolated melt porosity during open-system degassing (outgassing). Mean isolated porosity, for 𝜙 𝑥 = 0.5, increases from ~0.33 at the start of outgassing to ~0.67 by the end, doubling its trapped bubbles. For 𝜙 𝑥 = 0.7, isolated porosity increases from ~0.1 to ~0.2, implying gas retention and outgassing efficiency are strongly dependent on crystallinity.Outgassing occurs rapidly via fracturing at porosities < 0.1 when 𝜙 𝑥 ≥ 0.7. Fracturing and bubble coalescence are both inefficient outgassing mechanisms at 𝜙 𝑥 = 0.5 due to viscoelastoplastic deformation, which leads to an increase of isolated porosity. Between 𝜙 𝑥 of 0.5 and 0.7, samples sustained a three-fold difference in isolated porosity, implying that gas retention and eruptive behavior of crystal-rich magmas may be controlled by the onset and efficacy of crack-dominated outgassing and can be modulated by relatively small changes in crystallinity.

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Outgassing through magmatic fractures enables effusive eruption of silicic magma

Cited by 9 publications

References 91 publications

Experimental Evidence of Primary Permeability at Very Low Gas Content in Crystal‐Rich Silicic Magma

Experimental Evidence of Primary Permeability at Very Low Gas Content in Crystal‐Rich Silicic Magma

Pre‐Eruptive Outgassing and Pressurization, and Post‐Fragmentation Bubble Nucleation, Recorded by Vesicles in Breadcrust Bombs From Vulcanian Activity at Guagua Pichincha Volcano, Ecuador

Release the crackin': The influence of brittle behavior on gas retention in crystal-rich magma

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