The influence of olivine metastability on deep subduction of oceanic lithosphere

The dynamics of subduction of oceanic lithosphere is mainly controlled by t hermal buoyancy forces and mineralogy. In self-consistent models, the influ ence of metastable olivine (MO) on the dynamics and evolution of subducting oceanic lithosphere is investigated. We consider both phase boundaries - o livine (Ol) to spinel (Sp) (410 km) and Sp to perovskite (Pv) + magnesiowas tite (Mw) (660 km) - treating the kinetics of the phase transition in a sim plified way. While models do not allow the formation of MO penetrate straig ht 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, ou r models show that the effect of MO to slow down subduction velocities with in the transition zone is rather moderate. (C) 2000 Elsevier Science B.V. A ll rights reserved.