Anisotropic rheology of a cubic medium and implications for geological materials | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Anisotropic rheology of a cubic medium and implications for geological materials

Type de publication:

Journal Article

Source:

Geophysical Journal International, Volume 170, Ticket 2, p.876-885 (2007)

ISBN:

0956-540X

Numéro d'accès:

ISI:000248846600032

Mots-clés:

DEFORMATION; POLYCRYSTALS; RINGWOODITE; GENERATION; MODELS; FLOW

Résumé:

<p>Dislocation creep, which is the dominant deformation mechanism in the upper mantle, results in a non-Newtonian anisotropic rheology. The implication of non-Newtonian theology has been quite extensively studied in geodynamic models but the anisotropic aspect remains poorly investigated. In this paper, we propose to fill this gap by (1) introducing a simple mathematical description of anisotropic viscosity and (2) illustrating the link between plastic crystal deformation and bulk material rheology. The study relies on the highest symmetry of the anisotropic tensor, a cubic symmetry, for which anisotropy is characterized by one parameter only, 6. Firstorder implications of anisotropy are quantitatively explored as a function of 6. The effective theology of the material is described as a function of the orientation of the crystals and of the imposed stress and the validity of the isotropic approximation is discussed. The model, applied Ln to ringwoodite, a cubic crystal with spinel-type structure, predicts that the dynamics of the E transition zone in the Earth's mantle is going to be strongly affected by mechanical anisotropy.</p>

Notes:

Geophys. J. Int.Pouilloux, Laurent Kaminski, Edouard Labrosse, Stephane 26 BLACKWELL PUBLISHING