Silicic conduits as supersized tuffisites: Clastogenic influences on shifting eruption styles at Cordón Caulle volcano (Chile)

Schipper, C. Ian; Castro, Jonathan M.; Kennedy, Ben; Tuffen, Hugh; Whattam, Jack; Wadsworth, Fabian B.; Paisley, Rebecca; Fitzgerald, Rebecca H.; Rhodes, Emma; Schaefer, Lauren N.; Ashwell, P. A.; Forte, Pablo; Seropian, Gilles; Alloway, Brent V.

doi:10.1007/s00445-020-01432-1

Cited by 23 publications

(67 citation statements)

References 80 publications

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“…If passive outgassing through fractures in the upper conduit and conduit walls occurs then the eruption will be effusive, with the converse of exsolved volatile retention in the magma causing overpressure and an explosive eruption Gonnermann and Manga 2003;Gonnermann 2015;. Therefore, there is the potential that previous outgassing pathways, especially within the central conduit, be filled by impermeable material and cause localised explosive conditions and a hybrid effusive-explosive eruption (Gardner et al 2017;Cassidy et al 2018;Gardner et al 2018;Schipper et al 2021).…”

Section: Figure 12 Schematic Of Typical Effusive Open System (A) and Explosive Closed System (B) Eruptions Adapted Frommentioning

confidence: 99%

“…Current imaging techniques permit investigation of changes in the morphology of rocks. Scanning electron microscopy (SEM), and photomicrography can be used to get high-definition images of polished surfaces, and x-ray computed tomography (XCT) can permit volumes of a sample to be investigated in 3D (Shea et al 2010;Cashman and Sparks 2013;Schipper et al 2021). SEM imagery provides very high resolution surface imagery by scanning the surface of the material with a focused electron beam, these then interact with the surface atoms producing various signals making the image that is produced (Desbois et al 2011).…”

Section: Investigating Internal Texturesmentioning

confidence: 99%

“…This sintering can happen at varying timescales from minutes to tens of hours and change the outgassing capacity of the melt completely. It is one explanation for volcanoes going through effusive-explosive transitions within eruption sequences (Rust and Cashman 2004;Cashman and Sparks 2013;Schipper et al 2021). When these pathways are filled with sintered ash and preserved within a rock they are commonly referred to as tuffisites (Schipper et al 2015;Cassidy et al 2018;Whattam 2019).…”

Section: Sinteringmentioning

confidence: 99%

“…Sintering can even form obsidian if the particles are heated for a long enough time Gardner et al 2017;Gardner et al 2018;Gardner et al 2019;Schipper et al 2021).…”

Section: Sinteringmentioning

confidence: 99%

“…Although sintering can form obsidians, the newly formed obsidians retain distinctive clastogenic textures (Fig. 1.5) unless pressure is high enough to allow compaction and reabsorption of bubbles within the obsidian to form a homogenous texture (Rust and Cashman 2004;Wadsworth et al 2014;Schipper et al 2021). As the material progressively sinters, porosity decreases (Fig.…”

Section: Sinteringmentioning

confidence: 99%

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The good, the bad, and the bubbly: Textural controls on secondary vesiculation of silicic magma through thermal heating

Jones¹

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<p>Volcanic eruptions are driven by magma buoyancy caused by volatiles exsolving to form a separate gas phase. Gas overpressurization within the melt and subsequent fragmentation determines whether an eruption will be explosive (fragmentation) or effusive (no fragmentation). Therefore, a thorough understanding of factors which affect the ability of a melt to exsolve and retain or lose these volatiles effectively is required. Bubble nucleation and subsequent growth are the processes by which volatiles exsolve from the melt into an exsolved gas phase. As continued vesiculation occurs, bubbles may begin to interact and coalesce at a point called the percolation threshold, permeable pathways through the melt will then form until the permeability threshold is reached allowing volatiles to outgas, reducing overpressure. Currently, research has focused on the effects that pressure, temperature, and composition have on volatile solubility and eventual vesiculation. However, erupted bombs consisting of assemblages of heterogenous pyroclasts that were subsequently sintered and welded into a conduit-forming plug during the Cordón Caulle 2011-2012 eruption display vesiculation trends within naturally occurring obsidian pyroclasts formed by sintering of particles or quenched melt that cannot be resolved by volatile solubility effects alone. The erupted products have consistently low volatile contents with little variability present across erupted samples (0.07-0.32 wt. % H2O). Within these pyroclasts, the heterogeneity of internal textures is visible when viewed using backscattered electron (BSE) imaging or X-ray computed tomography (XCT) as clear borders exist between regions that are of a clastogenic (sintered) origin, of a quenched melt origin, or formed by variable forms of vesiculation. The heterogeneity of internal textures present within even a obsidian pyroclastic domain led to the hypothesis that foaming discrepancies observed within individual clasts were due to pre-existing textures promoting or inhibiting secondary vesiculation in the shallow conduit. This secondary vesiculation occurs through near isobaric temperature increases in the shallow conduit, following primary vesiculation and volatile exsolution associated with isothermal decompression from storage at depth. To test this hypothesis, obsidian samples of 1cm x 1-2cm x 1-3cm were heated above their glass transition temperature (Tg), between 850-910°C, to allow obsidians to vesiculate as the melt would have in the conduit. The textures of the samples were characterised before and after heating using x-ray computed tomography. The results show that within the slightly volatile supersaturated samples variable foaming was observed for each independent texture within obsidian pyroclasts, with foaming preferentially occurring within regions that contained pre-existing, isolated bubbles. These experiments show that limited thermally driven in situ foaming of relatively dense clasts containing small isolated bubbles, can increase overpressure if the domain doesn’t expand as bubbles form without increasing permeability leading to gas overpressure within this smaller region and localised explosions in order to clear this blockage, explaining the hybrid effusive-explosive eruptions observed at Cordón Caulle.</p>

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Section: Figure 12 Schematic Of Typical Effusive Open System (A) and Explosive Closed System (B) Eruptions Adapted Frommentioning

confidence: 99%

Section: Investigating Internal Texturesmentioning

confidence: 99%

Section: Sinteringmentioning

confidence: 99%

“…Sintering can even form obsidian if the particles are heated for a long enough time Gardner et al 2017;Gardner et al 2018;Gardner et al 2019;Schipper et al 2021).…”

Section: Sinteringmentioning

confidence: 99%

Section: Sinteringmentioning

confidence: 99%

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The good, the bad, and the bubbly: Textural controls on secondary vesiculation of silicic magma through thermal heating

Jones¹

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Microlite crystallization during eruptions at Mt. Mazama: implications for magma ascent

O’Donnell

Gardner

2022

Contrib Mineral Petrol

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Obsidian pyroclasts in the Yellowstone-Snake River Plain ignimbrites are dominantly juvenile in origin

et al. 2021

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Dense, glassy pyroclasts found in products of explosive eruptions are commonly employed to investigate volcanic conduit processes through measurement of their volatile inventories. This approach rests upon the tacit assumption that the obsidian clasts are juvenile, that is, genetically related to the erupting magma. Pyroclastic deposits within the Yellowstone-Snake River Plain province almost without exception contain dense, glassy clasts, previously interpreted as hyaloclastite, while other lithologies, including crystallised rhyolite, are extremely rare. We investigate the origin of these dense, glassy clasts from a coupled geochemical and textural perspective combining literature data and case studies from Cougar Point Tuff XIII, Wolverine Creek Tuff, and Mesa Falls Tuff spanning 10 My of silicic volcanism. These results indicate that the trace elemental compositions of the dense glasses mostly overlap with the vesiculated component of each deposit, while being distinct from nearby units, thus indicating that dense glasses are juvenile. Textural complexity of the dense clasts varies across our examples. Cougar Point Tuff XIII contains a remarkable diversity of clast appearances with the same glass composition including obsidian-within-obsidian clasts. Mesa Falls Tuff contains clasts with the same glass compositions but with stark variations in phenocryst content (0 to 45%). Cumulatively, our results support a model where most dense, glassy clasts reflect conduit material that passed through multiple cycles of fracturing and sintering with concurrent mixing of glass and various crystal components. This is in contrast to previous interpretations of these clasts as entrained hyaloclastite and relaxes the requirement for water-magma interaction within the eruptive centres of the Yellowstone-Snake River Plain province.

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Silicic conduits as supersized tuffisites: Clastogenic influences on shifting eruption styles at Cordón Caulle volcano (Chile)

Cited by 23 publications

References 80 publications

The good, the bad, and the bubbly: Textural controls on secondary vesiculation of silicic magma through thermal heating

The good, the bad, and the bubbly: Textural controls on secondary vesiculation of silicic magma through thermal heating

Microlite crystallization during eruptions at Mt. Mazama: implications for magma ascent

Obsidian pyroclasts in the Yellowstone-Snake River Plain ignimbrites are dominantly juvenile in origin

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