Pure climb creep mechanism drives flow in Earth’s lower mantle

Francesca Boioli (1) , Philippe Carrez (2) , Patrick Cordier (1) , Benoît Devincre (3) , Karine Gouriet (4) , Pierre Hirel (1) , Antoine Kraych (5) , Sebastian Ritterbex (1)

1 UMET - Unité Matériaux et Transformations - UMR 8207
2 LSPES - Laboratoire de structures et propriétés de l'état solide - UMR 8008
3 LEM - ONERA - CNRS - Laboratoire d'étude des microstructures [Châtillon]
4 LP3 - Laboratoire Lasers, Plasmas et Procédés photoniques
5 ILM - Institut Lumière Matière [Villeurbanne]

At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics. The calculation yields to an original dominant creep behavior for lower mantle silicates where strain is produced by dislocation climb, which is very different from what can be activated under high stresses under laboratory conditions. This mechanism, named pure climb creep, is grain-size–insensitive and produces no crystal preferred orientation. In comparison to the previous considered diffusion creep mechanism, it is also a more efficient strain-producing mechanism for grain sizes larger than ca. 0.1 mm. The spe-cificities of pure climb creep well match the seismic anisotropy observed of Earth's lower mantle.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Francesca Boioli, Philippe Carrez, Patrick Cordier, Benoît Devincre, Karine Gouriet, et al.. Pure climb creep mechanism drives flow in Earth’s lower mantle. Science Advances , 2017, 3 (3), ⟨10.1126/sciadv.1601958⟩. ⟨hal-01637562⟩