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In this section an overview of the most important on-going projects is given. Information concerning recently-completed projects can be obtained from the publication lists of sections 4.1 and 4.2. Please note that the following contributions should not be cited.
 

3.1 Phase Transformations, Deformation and Properties of Mantle Minerals

With increasing depth in the Earth´s mantle, minerals that are stable at low pressure undergo phase transformations to higher-density phases. As a consequence, the mantle is mineralogically-layered with olivine, pyroxenes and garnet dominating in the upper mantle (to a depth of 410 km), and the (Mg,Fe)₂SiO₄ polymorphs (wadsleyite and ringwoodite) and garnet dominating between 410 and 660 km. Silicate perovskite + magnesiowüstite are the main phases present in the lower mantle below 660 km. The transformations between these phases, which occur primarily at the depths of 410 and 660 km, have important effects on the dynamics of deep subduction as well as large-scale convection in the mantle. It is therefore important to characterise the physical and chemical properties of high-pressure phases in order to understand mantle dynamics. The mechanisms and kinetics of phase transformations, as discussed by several contributions in this section, determine the mineralogical structure, rheology, buoyancy forces and state of stress in subducting lithospheric plates. The rheology of the transition zone and lower mantle controls mantle convection and the results of the first study of plastic deformation of (Mg,Fe)₂SiO₄ ringwoodite at 16 GPa and 1400-1600 K are presented here. The kinetics of grain growth in polyphase rocks is also important for rheology because grain growth limits the duration of superplastic (grain-size sensitive) deformation, which occurs when grain sizes are very small. The final contributions in this section present results of studies of cation diffusion and electrical conduction in the high-pressure mantle minerals wadsleyite and ringwoodite. Both of these processes are found to be much faster than in olivine (the low-pressure polymorph), a result that has important implications for the defect chemistries of these phases as well as for rates of reaction and equilibration in the deep mantle.