Vibro-agitation of chambered magma

Davis, Matthew H.; Koenders, M. A.; Petford, Nick

doi:10.1016/j.jvolgeores.2007.07.012

Cited by 35 publications

(21 citation statements)

References 46 publications

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“…Instabilities propagating into the crust from the top down have been invoked for Icelandic volcanic systems, with progressive magma flow at depth responding to pressure changes in the shallow system [Tarasewicz et al, 2012]. The role of tectonics in enhancing, or even triggering, destabilization [e.g., Davis et al, 2007;Gottsmann et al, 2009] would benefit from closer study.…”

Section: Discussionmentioning

confidence: 99%

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Christopher

Blundy

Cashman

et al. 2015

Geochem Geophys Geosyst

125

107

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Activity since 1995 at Soufrière Hills Volcano (SHV), Montserrat has alternated between andesite lava extrusion and quiescence, which are well correlated with seismicity and ground deformation cycles. Large variations in SO 2 flux do not correlate with these alternations, but high and low HCl/SO 2 characterize lava dome extrusion and quiescent periods respectively. Since lava extrusion ceased (February 2010) steady SO 2 emissions have continued at an average rate of 374 tonnes/day (6 140 t/d), and incandescent fumaroles (temperatures up to 610 o C) on the dome have not changed position or cooled. Occasional short bursts (over several hours) of higher ( 10x) SO 2 flux have been accompanied by swarms of volcano-tectonic earthquakes. Strain data from these bursts indicate activation of the magma system to depths up to 10 km. SO 2 emissions since 1995 greatly exceed the amounts that could be derived from 1.1 km 3 of erupted andesite, and indicating extensive partitioning of sulfur into a vapour phase, as well as efficient decoupling and outgassing of sulfur-rich gases from the magma. These observations are consistent with a vertically extensive, crustal magmatic mush beneath SHV. Three states of the magmatic system are postulated to control degassing. During dormant periods (10 3 to 10 4 years) magmatic vapour and melts separate as layers from the mush and decouple from each other. In periods of unrest (years) without eruption, melt and fluid layers become unstable, ascend and can amalgamate. Major destabilization of the mush system leads to eruption, characterized by magma mixing and release of volatiles with different ages, compositions and sources.

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Section: Discussionmentioning

confidence: 99%

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Christopher

Blundy

Cashman

et al. 2015

Geochem Geophys Geosyst

125

107

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“…Although Jousset et al (2013) stress that the main factor causing over-pressurisation at Merapi in 2010 was related to magmatic influx and ascent, it is possible that with the magmatic system already at a critical pressurised stage, a small external force can affect the gas phase, promoting rapid degassing, fragmentation and eruption of an already unstable system (e.g. Brodsky et al 1998;Davis et al 2007;Walter et al, 2007). The melt inclusions and clinopyroxene hosts shed light on the magmatic plumbing system prior to the two most recent eruptions of Merapi and reveal an influx of deeper magma during the 2010 eruption, which was a key factor in determining the eruptive dynamics of the cataclysmic 2010 eruption.…”

Section: Clinopyroxene Crystallisation and Melt Inclusion Entrapmentmentioning

confidence: 99%

Pre- and syn-eruptive degassing and crystallisation processes of the 2010 and 2006 eruptions of Merapi volcano, Indonesia

Preece

Gertisser

Barclay

et al. 2014

Contrib Mineral Petrol

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clasts resulting from sub-plinian convective column collapse. This paper presents geochemical data for melt inclusions and their clinopyroxene hosts extracted from dense dome lava, grey scoria and white pumice generated during the peak of the 2010 eruption. These are compared with clinopyroxenehosted melt inclusions from scoriaceous dome fragments from the prolonged dome-forming 2006 eruption, to elucidate any relationship between pre-eruptive degassing and crystallisation processes and eruptive style. Secondary ion mass spectrometry analysis of volatiles (H 2 O, CO 2 ) and light lithophile elements (Li, B, Be) is augmented by electron microprobe analysis of major elements and volatiles (Cl, S, F) in melt inclusions and groundmass glass. Geobarometric analysis shows that the clinopyroxene phenocrysts crystallised at depths of up to 20 km, with the greatest calculated depths associated with phenocrysts from the white pumice. Based on their volatile contents, melt inclusions have reequilibrated during shallower storage and/or ascent, at depths of ~0.6-9.7 km, where the Merapi magma system is interpreted to be highly interconnected and not formed of discrete magma reservoirs. Melt inclusions enriched in Li show uniform "buffered" Cl concentrations, indicating the presence of an exsolved brine phase. Boron-enriched inclusions also support the presence of a brine phase, which helped to stabilise B in the melt. Calculations based on S concentrations in melt inclusions and groundmass glass require a degassing melt volume of 0.36 km 3 in order to produce the mass of SO 2 emitted during the 2010 eruption. This volume is approximately an order of magnitude higher than the erupted magma (DRE) volume. The transition between the contrasting eruptive styles in 2010 and 2006 is linked to changes in magmatic flux and changes in degassing style, with the explosive activity in 2010 driven by an influx of deep magma, which overwhelmed the shallower magma system and ascended rapidly, accompanied by closed-system degassing. AbstractThe 2010 eruption of Merapi (VEI 4) was the volcano's largest since 1872. In contrast to the prolonged and effusive dome-forming eruptions typical of Merapi's recent activity, the 2010 eruption began explosively, before a new dome was rapidly emplaced. This new dome was subsequently destroyed by explosions, generating pyroclastic density currents (PDCs), predominantly consisting of dark coloured, dense blocks of basaltic andesite dome lava. A shift towards open-vent conditions in the later stages of the eruption culminated in multiple explosions and the generation of PDCs with conspicuous grey scoria and white pumice Communicated by O. Müntener. Electronic supplementary materialThe online version of this article

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“…Mechanisms by which crystals may segregate from viscous silicic melt can include (1) compaction, most important at high crystallinities (>~70 vol% crystals; McKenzie, 1985;Philpotts et al, 1996), and (2) hindered/micro settling, most effi cient at intermediate crystallinities (~50-70 vol% crystals; Miller et al, 1988;Dufek and Bachmann, 2010). Such processes are typically slow (albeit poorly constrained) in high-viscosity magmas, but can be aided by external stresses (tectonic stresses, earthquakeinduced shaking; e.g., Davis et al, 2007) and/ or by volatiles injected or nucleating within the pore space of the crystal framework (Sisson and Bacon, 1999;Bachmann and Bergantz, 2006).…”

Section: Physical Mechanisms Of Crystal-melt Segregationmentioning

confidence: 99%

Cumulate fragments in silicic ignimbrites: The case of the Snake River Plain

Ellis

Bachmann

Wolff

2014

Geology

107

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Large silicic ignimbrites commonly erupt from compositionally variable reservoirs. Although ignimbrite compositional architecture is often consistent with evacuation of a single zoned magma body, other examples are better interpreted as the products of amalgamation of multiple discrete subvolcanic melt-rich lenses. For example, multiple populations of pyroxene crystals and glass fragments within single ignimbrites from the central Snake River Plain (Idaho, USA) support the multibatch model. This presents a conundrum in terms of magma generation and storage; if the crystal-poor silicic magma batches are not generated nearly in situ in the upper crust, they must traverse, and reside within, a thermally hostile environment with large temperature gradients, resulting in low survivability in their shallow magmatic hearths. Ubiquitous crystal aggregates in central Snake River Plain rhyolites hint at another model. These aggregates contain the same plagioclase, pyroxene, and oxide mineral compositions as single phenocrysts of the same minerals in their host rocks, but they have signifi cantly less silicic bulk compositions and lack quartz and sanidine, which occur as single phenocrysts in the deposits. These observations imply signifi cant crystallization followed by melt extraction from mushy margins of the magma reservoirs. The extracted melt then pools and continues to evolve (crystallizing sanidine and quartz) while the melt-depleted walls and/or fl oors provide an increasingly rigid and refractory network segregating the crystal-poor batches of magma. Such hot refractory margins insulate the crystal-poor lenses, allowing (1) extended residence in the upper crust, and (2) preservation of chemical heterogeneities among batches. In contrast, systems that produce cumulates richer in low-temperature phases (quartz, K-feldspars, and/or biotite) can melt extensively upon recharge, leading to less segregation of eruptible melt pockets and the formation of gradationally zoned ignimbrites.

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Vibro-agitation of chambered magma

Cited by 35 publications

References 46 publications

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Pre- and syn-eruptive degassing and crystallisation processes of the 2010 and 2006 eruptions of Merapi volcano, Indonesia

Cumulate fragments in silicic ignimbrites: The case of the Snake River Plain

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