Magma storage and mixing conditions for the 1953–1974 eruptions of Southwest Trident volcano, Katmai National Park, Alaska

Coombs, Michelle L.; Eichelberger, J. C.; Rutherford, M. J.

doi:10.1007/s004100000166

Cited by 111 publications

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“…These enclaves represent a pre-eruptive recharge event, where hot, basaltic andesite intruded into the base of the cooler, dacitic magma chamber (1). As the basaltic andesite chilled, volatile saturation occurred, and the andesite overturned, rapidly distributing enclaves and heat into the overlying dacite, triggering eruption in a manner analogous to that proposed for eruptions at Thera and elsewhere (2,3).…”

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confidence: 92%

Bang! Month-Scale Eruption Triggering at Santorini Volcano

Martin

Morgan

Jerram

et al. 2008

Science

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The time lag between intrusion of fresh, hot magma and an ensuing eruption is of critical importance in both understanding the triggering and mitigating the consequences of volcanic eruptions. This work looks at material erupted during 1925‐28 at the Nea Kameni volcanic center in Santorini, Greece, to determine this time scale. By exploiting Fe-Mg diffusion in olivine crystals, we constrained the intrusion-to-eruption time lag to between 3 and 10 weeks. These techniques have potential application at many volcanic centers; previously erupted material can be used to calibrate records of the short‐time scale processes common to many volcanic centers.

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confidence: 92%

Bang! Month-Scale Eruption Triggering at Santorini Volcano

Martin

Morgan

Jerram

et al. 2008

Science

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“…Mandeville et al 1996;Wolf and Eichelberger 1997;Coombs et al 2000;Cole et al 2001) suggest that andesitic magmas commonly involve mixing of acid and mafic melts. This mixing can lead to magmatic volatile saturation, which can potentially trigger volcanic eruptions (Hattori 1993) and may play a decisive role in the formation of magmatichydrothermal ore deposits (Dietrich et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Laser-ablation ICP-MS analysis of silicate and sulfide melt inclusions in an andesitic complex II: evidence for magma mixing and magma chamber evolution

Halter

Heinrich

Pettke

2004

Contrib Mineral Petrol

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Laser-ablation microanalysis of a large suite of silicate and sulfide melt inclusions from the deeply eroded, Cu-Au-mineralizing Farallo´n Negro Volcanic Complex (NW Argentina) shows that most phenocrysts in a given rock sample were not formed in equilibrium with each other. Phenocrysts in the andesitic volcano were brought together in dominantly andesitic-dacitic extrusive and intrusive rocks by intense magma mixing. This hybridization process is not apparent from macroscopic mingling textures, but is clearly recorded by systematically contrasting melt inclusions in different minerals from a given sample. Amphibole (and rare pyroxene) phenocrysts consistently contain inclusions of a mafic melt from which they crystallized before and during magma mixing. Most plagioclase and quartz phenocrysts contain melt inclusions of more felsic composition than the host rock. The endmember components of this mixing process are a rhyodacite magma with a likely crustal component, and a very mafic mantle-derived magma similar in composition to lamprophyre dykes emplaced early in the evolution of the complex. The resulting magmas are dominantly andesitic, in sharp contrast to the prominently bimodal distribution of mafic and felsic melts recorded by the inclusions. These results severely limit the use of mineral assemblages to derive information on the conditions of magma formation. Observed mineral associations are primarily the result of the mixing of partially crystallized magmas. The most mafic melt is trapped only in amphibole, suggesting pressures exceeding 350 MPa, temperatures of around 1,000°C and water contents in excess on 6 wt%. Upon mixing, amphibole crystallized with plagioclase from andesitic magma in the source region of porphyry intrusions at 250 MPa, 950°C and water contents of 5.5 wt%. During ascent of the extrusive magmas, pyroxene and plagioclase crystallized together, as a result of magma degassing at low pressures (150 MPa). Protracted extrusive activity built a large stratovolcano over the total lifetime of the magmatic complex (>3 m.y.). The mixing process probably triggered eruptions as a result of volatile exsolution.

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“…This is particularly interesting when one considers the undoubtedly frequent occurrence of recharge events and magma mixing as evidenced by hybrid magmas and phenocryst textures (e.g., Gardner et al 1995;Pallister et al 1996;Venezky and Rutherford 1997;Devine et al 1998;Clynne 1999;Tepley et al 1999Tepley et al , 2000Coombs et al 2000Coombs et al , 2003Izbekov et al 2004;Humphreys et al 2006;Andrews et al 2008;Waythomas et al 2010). This leads to the question of why banded pumice uncommonly erupts.…”

Section: Discussionmentioning

confidence: 99%

Thermal and rheological controls on the formation of mafic enclaves or banded pumice

Andrews

Manga

2014

Contrib Mineral Petrol

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Magma mixing can occur in a fluid manner to produce banded pumice or in a brittle manner to form enclaves. We propose that the critical control on mixing style is a competition between developing networks of crystals in the intruding magma that impart a strength to the magma and melting and disrupting those networks in the host. X-ray computed tomography analysis demonstrates that banded pumice from the 1915 Mt. Lassen eruption lacks crystal networks. In contrast, rhyodacite hosts with mafic enclaves from Chaos Crags contain welldeveloped networks of large crystals. We present a onedimensional conductive cooling model that predicts mixing style, either ductile or brittle, as a function of magma compositions, temperatures, and the size of the intruding dike. Our model relies on three assumptions: (1) Mixing is initiated by the injection of a hot dike into a cooler magma body with a yield strength; (2) when magma crystallinity exceeds a critical value, 13 vol% plagioclase, the magma develops a yield strength; and (3) when total crystallinity exceeds 40 vol%, the magma has a penetrative crystal network and is effectively solid. Importantly, because the two magmas are of different compositions, their crystallinities and viscosities do not have the same variations with temperature. As the intruding magma cools, it crystallizes from the outside in, while simultaneously, host magma temperature near the intruder rises. Mixing of the two magmas begins when the host magma is heated sufficiently to (1) disrupt the crystal network and (2) initiate convection. If the shear stress exerted by the convecting host magma on the dike is greater than the yield strength of the dike margin (and dike crystallinity does not exceed 40 %), then fluid mixing occurs, otherwise enclaves form by brittle deformation of the dike. Application of the model to magma compositions representative of Lassen and Chaos Crags shows that emplacement of dikes \1 m thick should produce enclaves, whereas thicker dikes should generate fluid mixing and form banded pumice within days to weeks of emplacement. Similar relationships apply to other modeled magmatic systems, including Pinatubo, Unzen, and Ksudach/Shtuybel' volcanoes. For all studied systems, the absolute size of the intruding dike, not just its proportion relative to the host, influences mixing style.

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Magma storage and mixing conditions for the 1953–1974 eruptions of Southwest Trident volcano, Katmai National Park, Alaska

Cited by 111 publications

References 0 publications

Bang! Month-Scale Eruption Triggering at Santorini Volcano

Bang! Month-Scale Eruption Triggering at Santorini Volcano

Laser-ablation ICP-MS analysis of silicate and sulfide melt inclusions in an andesitic complex II: evidence for magma mixing and magma chamber evolution

Thermal and rheological controls on the formation of mafic enclaves or banded pumice

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