Pressure effect on forsterite dislocation slip systems: Implications for upper-mantle LPO and low viscosity zone

Textures in deforming forsterite aggregates up to 8 GPa and 1673 K

“…Hence, our data do not allow determining the dominant slip system at lower depths. Texture measurements by Ohuchi et al (2011) and Ohuchi and Irifune (2014), however, lead to a dominant [001](100) or [001](hk0) at P ~7-11 GPa in wet and dry olivine, in agreement with the TEM work of Couvy et al (2004), the single crystal experiments of Raterron et al (2007Raterron et al ( , 2009Raterron et al ( , 2011Raterron et al ( , 2012, and predictions based on numerical modeling of Durinck et al (2005).…”

“…The change in observed textures above 6 GPa may be related to the transition of deformation mechanism expected at these conditions (e.g., Couvy et al 2004;Durinck et al 2005Durinck et al , 2007Raterron et al 2007Raterron et al , 2009Raterron et al , 2011Raterron et al , 2012Jung et al 2009) or a transition to a regime dominated by diffusion. Indeed, Nishihara et al (2014) have shown that both diffusion and dislocation creep play an important role in the rheology of forsterite aggregates.…”

“…In parallel, there is a vast literature demonstrating that the addition of water and/or stress can lead to other types of fabrics, compatible with other slip systems (e.g., Jung and Karato 2001;Katayama et al 2004;Jung et al 2006). Experiments also indicate a change of olivine and forsterite dominant deformation mechanism with increasing pressure (e.g., Couvy et al 2004;Mainprice et al 2005;Durinck et al 2005;Raterron et al 2007Raterron et al , 2009Raterron et al , 2011Raterron et al , 2012Ohuchi et al 2011;Ohuchi and Irifune 2014). Hence, the olivine fabric diagram obtained at low pressure cannot be easily translated at high pressure.…”

Lubrication of dislocation glide in forsterite by Mg vacancies: insights from Peierls-Nabarro modeling

“…Pressure changes the preferred dominant slip system of olivine, and much of the variation in seismic wave anisotropy in the upper mantle is explicable in terms of this pressure-induced transition (Mainprice et al 2005;Ohuchi et al 2011;Raterron et al 2016). At high pressure, the dominant slip system is [001](010), as this slip system hardens less in response to increasing pressure than the [100](010) slip system (Raterron et al 2011;Hilairet et al 2012). …”

Multiscale modeling of upper mantle plasticity: From single-crystal rheology to multiphase aggregate deformation

“…that there is no significant differences between the mechanisms responsible for deformations in the laboratory and along mantle geotherms. This assumption in not verified for mantle aggregates deforming in the dislocation creep regime, since olivine and clinopyroxenes (CPx) exhibit marked transitions induced by pressure in their dominant dislocation slip systems (Couvy et al, 2004;Raterron et al, 2007Raterron et al, , 2011Raterron et al, , 2012Amiguet et al, 2009;Jung et al, 2009;Ohuchi et al, 2011;). Besides, olivine and pyroxenes slip systems exhibit different stress sensitivities (e.g., Bai et al, 1991;Raterron and Jaoul, 1991) which cannot be accounted for by a single n exponent in the rheological law.…”