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Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

Pleše Pia, Higgins Michael D., Mancini L., Lanzafame G., Brun F., Fife J. L., Casselman J. et Baker Don R.. (2018). Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas. Lithos, 296-299, p. 532-546.

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URL officielle: https://doi.org/10.1016/j.lithos.2017.11.024

Résumé

Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a timeevolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, realtime 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

Type de document:Article publié dans une revue avec comité d'évaluation
Volume:296-299
Pages:p. 532-546
Version évaluée par les pairs:Oui
Date:Janvier 2018
Sujets:Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Mots-clés:heterogeneous bubble nucleation, volcanic degassing, 4D in situ tomography, 3D tomography, silicate crystals, nucléation hétérogène des bulles, dégazage volcanique, tomographie in situ 4D, tomographie 3D, cristaux de silicate
Déposé le:17 juill. 2018 18:42
Dernière modification:17 juill. 2018 18:42
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