Open AccessAnisotropic rheology of a cubic medium and implications for geological materials
Author(s) -
Pouilloux Laurent,
Kaminski Edouard,
Labrosse Stéphane
Publication year - 2007
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2007.03461.x
Subject(s) - anisotropy , rheology , isotropy , newtonian fluid , materials science , dislocation creep , viscosity , condensed matter physics , creep , thermodynamics , physics , composite material , optics
SUMMARY Dislocation creep, which is the dominant deformation mechanism in the upper mantle, results in a non‐Newtonian anisotropic rheology. The implication of non‐Newtonian rheology 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, δ. First‐order implications of anisotropy are quantitatively explored as a function of δ. The effective rheology 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 to ringwoodite, a cubic crystal with spinel‐type structure, predicts that the dynamics of the transition zone in the Earth's mantle is going to be strongly affected by mechanical anisotropy.