Degassing cascades in a shear-thinning viscoelastic fluid

Vidal, Valérie; Soubiran, François; Divoux, Thibaut; Géminard, Jean‐Christophe

doi:10.1103/physreve.84.066302

Cited by 7 publications

(6 citation statements)

References 51 publications

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“…In a magma the CGS would correspond to the free escape of the gas. A similar behaviour is observed in degassing cascades in a shearthinning fluid (Vidal et al, 2011). Interactions between trains of bubbles and the fluid lead to complex interactions between bubbles.…”

Section: Gas Interaction Within a High Crystallinity Mushsupporting

confidence: 53%

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Textures and melt-crystal-gas interactions in granites

Vigneresse¹

2015

Geoscience Frontiers

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a b s t r a c tFelsic intrusions present ubiquitous structures. They result from the differential interactions between the magma components (crystal, melt, gas phase) while it flows or when the flow is perturbed by a new magma injection. The most obvious structure consists in fabrics caused by the interactions of rotating grains in a flowing viscous melt. New magma inputs through dikes affect the buk massif flow, considered as global within each mineral facies. A review of the deformation and flow types developing in a magma chamber identifis the patterns that could be expected. It determines their controlling parameters and summarizes the tools for their quantification. Similarly, a brief review of the rheology of a complex multiphase magma identifies and suggests interactions between the different components. The specific responses each component presents lead to instability development. In particular, the change in vorticity orientation, associated with the switch between monoclinic to triclinic flow is a cause of many instabilities. Those are preferentially local. Illustrations include fabric development, shear zones and flow banding. They depend of the underlying rheology of interacting magmas. Dikes, enclaves, schlieren and ladder dikes result from the interactions between the magma components and changing boundary conditions. Orbicules, pegmatites, unidirectional solidification textures and miarolitic cavities result from the interaction of the melt with a gaseous phase. The illustrations examine what is relevant to the bulk flow, local structures or boundary conditions. In each case a field observation illustrates the instability. The discussion reformulates instability observations, suggesting new trails for ther description and interpretation in terms of local departure to a bulk flow. A brief look at larger structures and at their evolution tries to relate these instabilities on a broader scale. The helical structures of the Rí cany pluton, Czech Republic and by the multiple granitic intrusions of Dolbel, Niger illustrate such events.Ó 2014, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Section: Gas Interaction Within a High Crystallinity Mushsupporting

confidence: 53%

“…A transitional state occurs between the two states. It suggests that the transition is an effect of the fluid rheology (Vidal et al, 2011). The flux of ascending bubbles is intermittent (Divoux et al, 2009).…”

Section: Gas Interaction Within a High Crystallinity Mushmentioning

confidence: 97%

Textures and melt-crystal-gas interactions in granites

Vigneresse¹

2015

Geoscience Frontiers

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“…In this regime, channels formation and collapse are observed intermittently. This dynamics strongly resembles the degassing dynamics, in the same experimental conditions (constant injection flowrate), through a layer of shear-thinning, viscoelastic fluid [50][51][52].…”

Section: Bubbles or Channels?mentioning

confidence: 59%

Flow and fracture in water-saturated, unconstrained granular beds

et al. 2015

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The injection of gas in a liquid-saturated granular bed gives rise to a wide variety of invasion patterns. Many studies have focused on constrained porous media, in which the grains are fixed in the bed and only the interstitial fluid flows when the gas invades the system. With a free upper boundary, however, the grains can be entrained by the ascending gas or fluid motion, and the competition between the upward motion of grains and sedimentation leads to new patterns. We propose a brief review of the experimental investigation of the dynamics of air rising through a water-saturated, unconstrained granular bed, in both two and three dimensions. After describing the invasion pattern at short and long time, a tentative regime-diagram is proposed. We report original results showing a dependence of the fluidized zone shape, at long times, on the injection flow rate and grain size. A method based on image analysis makes it possible to detect not only the fluidized zone profile in the stationary regime, but also to follow the transient dynamics of its formation. Finally, we describe the degassing dynamics inside the fluidized zone, in the stationary regime. Depending on the experimental conditions, regular bubbling, continuous degassing, intermittent regime or even spontaneous flow-to-fracture transition are observed.

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“…A second (and end‐member) option is that gas supply is highly periodic, a possibility proposed by several authors (e.g., Lesage et al, ; Ripepe et al, ) and that generates harmonic tremor in our thin‐caps model through a Dirac comb effect (Figures d, e, and f). Periodic gas supply could be controlled by rectified diffusion (Brodsky et al, ); the flow of bubbles through granular suspensions (i.e., crystal‐rich magma; Barth et al, ); the collapse of critically unstable bubble rafts, foams, or viscoelastic layers formed at the top of magma columns (Ritacco et al, ; Spina et al, ; Vidal et al, ); natural self‐organization of bubbles to produce gas waves (Manga, ; Michaut et al, ); and the coupling between gas exsolution and the pressure changes occurring below the permeable cap, as motivated by experiments performed with slightly open soda bottles (Hellweg, ; Soltzberg et al, ). These mechanisms may play an important role in generating periodic gas emissions in persistently outgassing volcanoes (e.g., Girona, Costa, Taisne, et al, ; Tamburello et al, ), although it is unclear whether they can supply gas at a sufficient degree of periodicity to produce a Dirac comb effect (Hagerty et al, ; Powell & Neuberg, ).…”

Section: Discussionmentioning

confidence: 99%

Origin of Shallow Volcanic Tremor: The Dynamics of Gas Pockets Trapped Beneath Thin Permeable Media

2019

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Linking volcano-seismic signals with subsurface processes is crucial to improve the forecasting of volcanic eruptions. One of the most enigmatic signals is shallow volcanic tremor, a highly periodic ground vibration that is typically sourced beneath the crater of active volcanoes, is long lasting (from minutes to years), appears during unrest periods, and frequently precedes eruptions. In this paper, we demonstrate that shallow tremor can be produced by periodic pressure oscillations emerging spontaneously beneath permeable media (e.g., fractured magma caps). These pressure oscillations are the result of three concurrent processes: (a) the transient porous flow of gases through the permeable cap; (b) the temporary accumulation of these gases beneath the cap, forming a gas pocket; and (c) the random supply of volatiles from deeper levels. For highly permeable media (≥10 −12 m 2 ; realistic for shallow volcanic edifices), the pressure in subsurface gas pockets is governed by the equation of a linear oscillator; hence, under proper conditions, periodic pressure oscillations emerge during the transfer of gases from the Earth's interior to the surface. Our model is consistent with geophysical data showing that the tremor source is localized at a fixed region and can explain the main characteristics of ground vibrations, including frequency gliding, variations of seismic amplitude prior to eruptions, and the different types of tremor observed. For thin permeable caps (<100 m), we find that different eruption mechanisms (e.g., magma ascent vs. cap sealing) leave distinct footprints in the tremor properties, thus opening new perspectives to forecast the type and style of impending eruptions.

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Degassing cascades in a shear-thinning viscoelastic fluid

Cited by 7 publications

References 51 publications

Textures and melt-crystal-gas interactions in granites

Textures and melt-crystal-gas interactions in granites

Flow and fracture in water-saturated, unconstrained granular beds

Origin of Shallow Volcanic Tremor: The Dynamics of Gas Pockets Trapped Beneath Thin Permeable Media

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