HR: 0800h
AN: V21C-0723    [Abstracts]
TI: Permeability, anisotropy and tortuosity measurements of pumices using X-ray computed microtomography
AU: * Degruyter, W
EM: wim.degruyter@terre.unige.ch
AF: Département de Minéralogie University of Geneva, 13 rue des Mara\ⁱchers, Geneva, 1205, Switzerland
AU: Bachmann, O
EM: bachmano@u.washington.edu
AF: Department of Earth and Space Sciences University of Washington, mailstop 351310, Seattle, WA 98195, United States
AU: Burgisser, A
EM: burgisse@cnrs-orleans.fr
AF: Institut des Sciences de la Terre d'Orléans - CNRS University of Orl\´{e}ans, 1A rue de la Férollerie, Orl\´{e}ans, 45071, France
AU: Malaspinas, O
EM: orestis.malaspinas@epfl.ch
AF: Laboratoire d'Ingénierie Numérique Ecole Polythechnique Fédérale de Lausanne, ME-Ecublens, Station 9, Lausanne, 1015, Switzerland
AU: Cnudde, V
EM: veerle.cnudde@ugent.be
AF: Department for Geology and Soil Science University of Ghent, Krijgslaan 281/S8, Gent, 9000, Belgium
AU: Masschaele, B
EM: bert.masschaele@ugent.be
AF: Department for Subatomic and Radiation Physics University of Ghent, Proeftuinstraat 86, Gent, 9000, Belgium
AB: X-ray computed microtomography (μCT) has become a widely-applied technique to obtain density maps of heterogeneous media; it allows gathering non-destructively qualitative observations as well as quantitative information on the 3D geometries of multi-phase samples. In this study, we obtained 3D images of different pumice types found in the rhyolitic Kos Plateau Tuff (KPT) deposits (160 ky, South Aegean Arc, Greece), and combined anisotropy and (geometrical) tortuosity measurements of these scans with permeability data to gain insights into the development of pathways through magmatic foam and how it affects syn-eruptive degassing. The rhyolitic KPT pumices are particularly prone to textural analysis because (1) the deposits are non-welded, (2) the high viscosity of the magma helped preserving information on the state of the magmatic foam in the conduit immediately prior to fragmentation (i.e., disruption of magma into pyroclastic fragments) and (3) pumices display variable macroscopic textures including tubular and near-spherical networks of bubbles. The stacks of grey-scale μCT images were cropped and segmented to obtain 3D binary volumes. These volumes were submitted to anisotropy and tortuosity measurements using existing softwares. Results suggest a significantly more convoluted path through the spherical bubble networks than the tubular bubble networks. To complement this geometrical characterisation of pumices, permeability values on the same binary volumes will be acquired using two numerical codes (one is based on a Finite Difference scheme, the other using the Lattice Boltzmann technique).
DE: 8428 Explosive volcanism
DE: 8430 Volcanic gases
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting