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Université d'Orléans |  |
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Université d'Orléans | |
| HAL: insu-00597327, version 1 |
| DOI: 10.1007/s00445-011-0472-1 |
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| Bulletin of Volcanology / Bull Volcanic Eruptions 73, 9 (2011) 1295-1309 |
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| Quantitative textural analysis of Vulcanian pyroclasts (Montserrat) using multi-scale X-ray computed microtomography: comparison with results from 2D image analysis |
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| Thomas Giachetti 1, 2Alain Burgisser 3 |
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| (2011) |
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| X-ray computed microtomography (μCT) was carried out on four pyroclasts from the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat. Three-dimensional data from multiple image stacks with different spatial resolutions (0.37, 4-8, and 17.4 μm px−1) were combined to generate size distributions of vesicles, inter-vesicle throats, crystals, and Fe-Ti oxides over a 3.4-860-μm size range, and to compare the results with those obtained by 2D image analysis on the same samples. Qualitative textural observations are in good agreement with those made in 2D, but μCT provides better resolution of textural features and spatial relationships. Calculation of size distributions requires automated decoalescence of the connected vesicle network. Problems related to this process, in part due to the high porosity of pumice, result in potential artefacts in the calculated size distributions, which are discussed in detail. The main modes of the 3D vesicle volume distributions are systematically shifted to larger sizes compared with those of the 2D distributions. Sample total vesicularities obtained in 3D are within 13 vol.% of those found in 2D, and within 10 vol.% of those measured by He-pycnometry. Total number densities of vesicles and Fe-Ti oxides from the two methods are consistent only to the first order, 3D values ranging from 37% to 309% of those in 2D. Vesicle coalescence, investigated by examining inter-vesicle throat size distributions, occurred in all pyroclasts between neighbouring vesicles of many sizes. The larger the vesicle, the more connected it is. |
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| 1: | Laboratoire Magmas et Volcans (LMV) |
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CNRS : UMR6524 – Institut de recherche pour le développement [IRD] – INSU – Université Blaise Pascal - Clermont-Ferrand II – Université Jean Monnet - Saint-Etienne |
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| 2: | Laboratoire de Géographie physique et environnementale (GEOLAB) |
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CNRS : UMR6042 – Université Blaise Pascal - Clermont-Ferrand II – Université de Limoges – Institut Sciences de l'Homme et de la Société |
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| 3: | Institut des Sciences de la Terre d'Orléans (ISTO) |
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Université d'Orléans – CNRS : UMR6113 – Université François Rabelais - Tours – INSU |
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| 4: | IRD R 163 |
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Institut de recherche pour le développement [IRD] |
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| subject | : | Sciences of the Universe/Earth Sciences/Volcanology Environmental Sciences/Global Changes |
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| X-ray computed microtomography - Vesicle size distribution - Vesicle number density - Coalescence - Vulcanian explosions - Soufrière Hills Volcano - Montserrat |
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| Attached file list to this document: | |||||
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| insu-00597327, version 1 | |
| http://hal-insu.archives-ouvertes.fr/insu-00597327 | |
| oai:hal-insu.archives-ouvertes.fr:insu-00597327 | |
| From: Nathalie Pothier | |
| Submitted on: Tuesday, 31 May 2011 15:36:24 | |
| Updated on: Friday, 18 November 2011 08:33:23 | |
