The role of diffusion-driven pure climb creep on the rheology of bridgmanite under lower mantle conditions

Riccardo Reali (1) , James A. van Orman (2) , Jeffrey S. Pigott (2) , Jennifer M. Jackson (3) , Francesca Boioli (1, 4) , Philippe Carrez (1) , Patrick Cordier (1)

1 UMET - Unité Matériaux et Transformations - UMR 8207
2 Case Western Reserve University [Cleveland]
3 CALTECH - California Institute of Technology
4 LEM, UMR 104 CNRS-ONERA, Université Paris Saclay (COmUE) [Châtillon]

The viscosity of Earth's lower mantle is poorly constrained due to the lack of knowledge on some fundamental variables that affect the deformation behaviour of its main mineral phases. This study focuses on bridgmanite, the main lower mantle constituent, and assesses its rheology by developing an approach based on mineral physics. Following and revising the recent advances in this field, pure climb creep controlled by diffusion is identified as the key mechanism driving deformation in bridgmanite. The strain rates of this phase under lower mantle pressures, temperatures and stresses are thus calculated by constraining diffusion and implementing a creep theoretical model. The viscosity of MgSiO 3 bridgmanite resulting from pure climb creep is consequently evaluated and compared with the viscosity profiles available from the literature. We show that the inferred variability of viscosity in these profiles can be fully accounted for with the chosen variables of our calculation, e.g., diffusion coefficients, vacancy concentrations and applied stresses. A refinement of these variables is advocated in order to further constrain viscosity and match the observables.

Mots clés: BRIDGMANITE; CLIMB CREEP; THE RHEOLOGY

Mots clés: LA RHÉOLOGIE; FLUAGE ASCENSIONNEL

Domaines: Géophysique [physics.geo-ph]

Riccardo Reali, James A. van Orman, Jeffrey S. Pigott, Jennifer M. Jackson, Francesca Boioli, et al.. The role of diffusion-driven pure climb creep on the rheology of bridgmanite under lower mantle conditions. Scientific Reports, 2019, 9, pp.2053. ⟨10.1038/s41598-018-38449-8⟩. ⟨hal-02181730⟩