The effect of dynamic recrystallization on olivine crystal preferred orientations in mantle xenoliths deformed under varied stress conditions

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization

“…These LPOs also resemble the AG-type (Mainprice 2007) or [010]-fiber pattern (Tommasi et al 1999). The mechanisms proposed for the formation of the AG-type are simultaneous activation of [100] and [001] slip systems (Mainprice et al 2005;Tommasi et al 2000), presence of the partial melt (Holtzman et al 2003), transpression (Tommasi et al 1999), and recrystallization (Falus et al 2011). Within these mechanisms, simultaneous activation of [100] and [001] slip direction induced by the presence of water can be the possible mechanism for producing the AG-type LPO in the peridotite samples from the Lindås Nappe complex.…”

Deformation and hydration of the lithospheric mantle beneath the Kaapvaal craton, South Africa

“…Three olivine CPO patterns were identified: (1) (Tommasi et al, 1999), from changes in dominant glide system due to variations in physical parameters (differential stress, pressure, or water contents in olivine) during deformation, or from recrystallization (Falus et al, 2011;Tommasi et al, 2008). However, transpressional deformation should also result in dispersion of orthopyroxene [001] axes in the foliation plane, which is not observed in most studied peridotites, which show predominantly point distribution of orthopyroxene [001] axes (Fig.…”

Modeling the effect of subgrain rotation recrystallization on the evolution of olivine crystal preferred orientations in simple shear

“…Indeed, when the CPO of parent and recrystallized grains could be measured separately, the latter shows a higher dispersion (Nicolas et al, 1973;Tommasi et al, 2000;Zhang et al, 2000;Falus et al, 2011). This suggests that dynamic recrystallization contributes to weaken the CPO.…”

“…Deformed crystals are crosscut by numerous low-angle tilt boundaries parallel to the (100) plane. Analysis of the misorientation across these boundaries and TEM data shows that they are essentially composed by dislocations of the [100]{0kl} systems (e.g., Green and Radcliffe, 1972;Buiskool Toxopeus and Boland, 1976;Falus et al, 2011). Deformation bands with misorientations ranging from 8 to 32 • were also observed in deformation experiments on olivine single crystals where the available slip systems could not accommodate the fixed boundary conditions at the contact with the pistons (Demouchy et al, 2013).…”

“…We opted to investigate an alternative recrystallization process: continuous dynamic recrystallization (CDRX), focusing on the consequences of the formation of subgrains on the CPO evolution and mechanical behavior of an olivine polycrystal deformed in simple shear. This choice is justified by microstructural observations in naturally and experimentally deformed peridotites, like the high proportion of low-angle grain boundaries with misorientations accommodated by rotations around {0kl} axes and the predominance of recrystallized grains with sizes similar to the subgrains (e.g., Falus et al, 2011), which suggest that, in olivine-rich rocks, nucleation during dynamic recrystallization occurs essentially by progressive misorientation of low-angle boundaries.…”