The influence of olivine metastability on deep subduction of oceanic lithosphere

The dynamics of subduction of oceanic lithosphere is mainly controlled by thermal buoyancy forces and mineralogy. In self-consistent models, the influence of metastable olivine (MO) on the dynamics and evolution of subducting oceanic lithosphere is investigated. We consider both phase boundaries - olivine (Ol) to spinel (Sp) (410 km) and Sp to perovskite (Pv) + magnesiowastite (Mw) (660 km) - treating the kinetics of the phase transition in a simplified way. While models do not allow the formation of MO penetrate straight into the lower mantle, slabs with a sufficient amount of MO flatten out at the 660-km boundary before penetrating at a later stage. Furthermore, our models show that the effect of MO to slow down subduction velocities within the transition zone is rather moderate. (C) 2000 Elsevier Science B.V. All rights reserved.