Tube pumices as strain markers of the ductile–brittle transition during magma fragmentation

Martı́, Joan; Soriano, Carles; Dingwell, Donald B.

doi:10.1038/45219

Cited by 69 publications

(39 citation statements)

References 19 publications

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“…It is thus possible to use observed size distributions to infer the details of the operation of these processes during eruption. In highly energetic silicic eruptions, magma fragmentation (Alidibirov 1994;Alidibirov and Dingwell 1996;Alidibirov and Panov 1998;Zhang 1999) severely alters vesicularity as bubbly liquid converts to gassy spray (Marti et al 1999;Zhang 1999;Sahagian 1999). We limit our discussion to unfragmented lavas that commonly result from effusive, Hawaiiantype eruptions.…”

Section: Introductionmentioning

confidence: 98%

Synchrotron X-ray computed microtomography: studies on vesiculated basaltic rocks

Song

Jones

Lindquist³

et al. 2001

Bull Volcanol

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Synchrotron X-ray computed microtomography (CMT) was applied to five basalt samples from different locations in order to determine the microgeometrical structures and physical properties of vesicles. Two vesiculated basaltic lavas and one calcite-filled vesiculated basaltic lava were collected from the Lesotho Highland, South Africa, and two basaltic scoria tephra were taken from the Lungkuan Volcano Group in northeast China. They were examined with CMT on the X27C beam line of the Brookhaven National Synchrotron Light Source. The voxel size varied from 10 to 20 µm depending on the chosen field of view of the tomographic instrument. A fast-filtered back-transform (FFBT) algorithm was employed in the tomographic reconstruction. A 3D image geometry analysis package was used to measure the vesicularity, specific surface area and interconnectivity of the vesicles. The results of the analyses showed that the bubbles have roughly spheroidal forms of different sizes. Vesicularity ranged from 45% for lavas to 80% for scoria. At least 90% of the vesicles are interconnected. Specific surface area was determined both by counting voxel faces and by use of two-point correlation functions.

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Section: Introductionmentioning

confidence: 98%

Synchrotron X-ray computed microtomography: studies on vesiculated basaltic rocks

Song

Jones

Lindquist³

et al. 2001

Bull Volcanol

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“…The presence of spherical (frothy) and elongated (tube) bubbles in pumices erupted synchronously during magma ascent records zones with respectively low and high strain rates, that develop by simple or pure shear within the conduit during ascent (Marti et al 1999;Polacci et al 2003;Bouvet de Maisonneuve et al 2008). As a result of higher (Darcian and inertial) permeability in the direction of elongation, magma outgassing will be more efficient in strongly sheared areas (Okumura et al 2009).…”

Section: Volcanological Implicationsmentioning

confidence: 99%

“…1d-f and 2). Such types of pumices are frequently observed in deposits of explosive caldera-forming silicic eruptions (Marti et al 1999;Polacci et al 2003;Polacci 2005;Wright et al 2006). …”

Section: Samplesmentioning

confidence: 99%

“…The KPT pumices display macroscopic textures ranging from tubular (i.e., tube pumice) to near-spherical (i.e., frothy pumice) networks of bubbles, suggesting that the magmatic foam in different parts of the conduit was exposed to variable strain (Marti et al 1999;Polacci et al 2003;Rosi et al 2004;Wright et al 2006) during ascent. A previous study on the KPT eruption (Bouvet de Maisonneuve et al 2008) reported highly variable permeabilities (variations over several orders of magnitude) of tube and frothy pumices for given porosities, implying that parameters other than porosity exerts a strong control on magma outgassing.…”

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confidence: 99%

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Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)

Degruyter

Burgisser

2009

Bull Volcanol

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X-ray computed microtomography (µCT) was applied to pumices from the largest Quaternary explosive eruption of the active South Aegean Arc (the Kos Plateau Tuff; KPT) in order to better understand magma permeability within volcanic conduits. Two different types of pumices (one with highly elongated bubbles, tube pumice; and the other with near spherical bubbles, frothy pumice) produced synchronously and with identical chemical composition were selected for µCT imaging to obtain porosity, tortuosity, bubble size and throat size distributions. Tortuosity drops on average from 2.2 in frothy pumice to 1.5 in tube pumice. Bubble size and throat size distributions provide estimates for mean bubble size (~93-98 μm) and mean throat size (~23-29 μm). Using a modified Kozeny-Carman equation, variations in porosity, tortuosity, and throat size observed in KPT pumices explain the spread found in laboratory measurements of the Darcian permeability. Measured difference in inertial permeability between tube and frothy pumices can also be partly explained by the same variables but require an additional parameter related to the internal roughness of the porous medium (friction factor f 0 ). Constitutive equations for both types of permeability allow the quantification of laminar and turbulent gas escape during ascent of rhyolitic magma in volcanic conduits.

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“…At low Ca (bubbles closely spherical), the bubbly fluid or foam viscosity is generally greater than that of the liquid phase, while at high Ca (bubbles highly elongated) the bubbly fluid or foam viscosity is generally less than that of the liquid phase ]. The existence of tube pumice [Marti et al, 1999] suggests that Ca >> 1 for explosive volcanic flows. Microscope observation of fractured surfaces on foam fragments generated during high decompression ratio experiments often shows elongated bubbles, as illustrated by Phillips et al, [1995].…”

Section: Dynamic Similaritymentioning

confidence: 99%

Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system

Lane¹,

Chouet²,

Phillips³

et al. 2001

J. Geophys. Res.

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Abstract. Gas-liquid flows, designed to be analogous to those in volcanic conduits, are generated in the laboratory using organic gas-gum rosin mixtures expanding in a vertically mounted tube. The expanding fluid shows a range of both flow and pressure oscillation behaviors. Weakly supersaturated source liquids produce a low Reynolds number flow with foam expanding from the top surface of a liquid that exhibits zero fluid velocity at the tube wall; i.e., the conventional "no-slip" boundary condition. Pressure oscillations, often with strong long-period characteristics and consistent with longitudinal and radial resonant oscillation modes, are detected in these fluids. Strongly supersaturated source liquids generate more energetic flows that display a number of flow regimes. These regimes include a static liquid source, viscous flow, detached flow (comprising gas-pockets-at-wall and foamin-gas annular flow, therefore demonstrating strong radial heterogeneity), and a fully turbulent transonic fragmented or mist flow. Each of these flow regimes displays characteristic pressure oscillations that can be related to resonance of flow features or wall impact phenomena. The pressure oscillations are produced by the degassing processes without the need of elastic coupling to the confining medium or flow restrictors and valvelike features. The oscillatory behavior of the experimental flows is compared to seismoacoustic data from a range of volcanoes where resonant oscillation of the fluid within the conduit is also often invoked as controlling the observed oscillation frequencies. On the basis of the experimental data we postulate on the nature of seismic signals that may be measured during large-scale explosive activity.

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Tube pumices as strain markers of the ductile–brittle transition during magma fragmentation

Cited by 69 publications

References 19 publications

Synchrotron X-ray computed microtomography: studies on vesiculated basaltic rocks

Synchrotron X-ray computed microtomography: studies on vesiculated basaltic rocks

Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)

Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system

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