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Deformation experiments of bubble and crystal bearing magmas : rheological and microstructural analysis
Pistone M., Caricchi L., Ulmer P., Burlini L., Ardia P., Reusser E., Marone F., Arbaret L.
Journal of Geophysical Research 117, B05208 (2012) 1-39 - http://hal-insu.archives-ouvertes.fr/insu-00689606
Articles dans des revues avec comité de lecture
Planète et Univers/Sciences de la Terre/Volcanologie
Sciences de l'environnement/Milieux et Changements globaux
Deformation experiments of bubble and crystal bearing magmas : rheological and microstructural analysis
M. Pistone 1, Luca Caricchi 2, Pete Ulmer 1, L. Burlini 3, Paola Ardia 4, Éric Reusser 3, Federica Marone 5, Laurent Arbaret () 6
1 :  Institute for Geochemistry and Petrology
2 :  Department of Earth Sciences
University of Bristol
University of Bristol, Bristol BS8 1RJ
3 :  Institute of Geology, ETH Zürich
4 :  Department of Geology and Geophysics
University of Minnesota
5 :  The Swiss Light Source (SLS) (SLS-PSI)
Paul Scherrer Institut (PSI)
Paul Scherrer Institut 5232 Villigen PSI Suisse
6 :  Institut des Sciences de la Terre d'Orléans (ISTO)
Université d'Orléans – CNRS : UMR7327 – INSU – Bureau de Recherches Géologiques et Minières (BRGM)
Campus Géosciences 1A, rue de la Férollerie 45071 Orléans cedex 2
Simple shear deformation experiments on three-phase, hydrous, haplogranitic magmas, composed of quartz crystals (24-65 vol%), CO2-rich gas bubbles (9-12 vol%) and melt in different proportions, were performed with a Paterson-type rock deformation apparatus. Strain rates from 5*10-6 s-1 to 4*10-3 s-1 were applied at temperatures between 723 and 1023 K and at pressure of 200 MPa. The results show that the three-phase suspension rheology is strongly strain-rate dependent (non-Newtonian behavior). Two non-Newtonian regimes were observed: shear thinning (viscosity decreases with increasing strain rate) and shear thickening (viscosity increases with increasing strain rate). Shear thinning occurs in crystal-rich magmas (55-65 vol% crystals; 9-10 vol% bubbles) as a result of crystal size reduction and shear zoning. Shear thickening prevails in dilute suspensions (24 vol% crystals; 12 vol% bubbles), where bubble coalescence and outgassing dominate. At intermediate crystallinity (44 vol% crystals; 12 vol% bubbles) both shear thickening and thinning occur. Based on the microstructural observations using synchrotron radiation X-ray tomographic microscopy, bubbles can develop two different shapes: oblate at low temperature (< 873 K) and prolate at high temperature (> 873 K). These differences in shape are caused by different conditions of flow: unsteady flow, where the relaxation time of the bubbles is much longer than the timescale of deformation (oblate shapes); steady flow, where bubbles are in their equilibrium deformation state (prolate shapes). Three-phase magmas are characterized by a rheological behavior that is substantially different with respect to suspensions containing only crystals or only gas bubbles.

Journal of Geophysical Research (J. Geophys. Res. (B Solid Earth))
Publisher American Geophysical Union (AGU)
ISSN 0148-0227 

Swiss National Foundation (grant 200020-120221)
Acronyme NE/G012946/1
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2011JB008986.pdf(9.6 MB)