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Geology 39, 8 (2011) 747-750
Rheology and microstructure of experimentally deformed plagioclase suspensions
David Picard 1, Laurent Arbaret 1, Michel Pichavant 1, Rémi Champallier 1, Patrick Launeau 2

We present the result of the first deformation experiments at high-temperatures and high-pressures on synthetic magmatic suspensions of strongly anisometric particles. The results highlight the interplay between the rheological response and the development of microstructures and they demonstrate the critical importance of the shape of crystals on the mechanical behaviour of magmas. Plagioclase suspensions with two crystal fractions (0.38 and 0.52) were deformed both in compression and in torsion in a Paterson apparatus. With increasing crystal fraction, the rheological behaviour of the magmatic suspension evolves from nearly steady-state flow to shear weakening, this change being correlated with a microstructural evolution from a pervasive strain to a strain partitioning fabric. Magmatic suspensions of plagioclase have viscosities approximately five orders of magnitude higher than suspensions of equivalent crystallinities made of isometric particles such as quartz.
1 :  Institut des Sciences de la Terre d'Orléans (ISTO)
CNRS : UMR6113 – INSU – Université d'Orléans – Université François Rabelais - Tours
2 :  Laboratoire de Planétologie et Géodynamique de Nantes (LPGN)
CNRS : UMR6112 – INSU – Université de Nantes
Planète et Univers/Sciences de la Terre/Volcanologie

Sciences de l'environnement/Milieux et Changements globaux
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