Plastic Deformation and Deformation Fabric in Wadsleyite and Ringwoodite: Effects of Water and Grain-Size

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Karato 0105493 The interaction of convection currents in Earth's mantle with the mantle transition zone (410 to 660 km depth) affects the pattern of mantle circulation and hence evolution of this planet. This interaction depends strongly on the change in physical properties that occurs in the transition zone, particularly the rheological properties. To help understand the influence of rheological properties of transition zone materials on this interaction, the PI proposes to conduct experimental studies on plastic flow in transition zone minerals (wadsleyite and ringwoodite respectively) under the transition zone conditions with the emphasis on the effects of water and grain-size. Both grain-size and water can change significantly as convection currents go through the transition zone. The investigators will extend their previous studies into two new directions; (1) to investigate the effects of water on rheology and deformation fabric, and (2) to improve the quality of data by better-defined (constant strain-rate) deformation experiments and by stress measurements using the synchrotron radiation facility and transmission electron microscopy. These results will provide the first quantitative data set on the effects of water and grain-size on rheology and deformation fabric of major transition zone minerals and a firm basis for interpretation of seismic anisotropy in the transition zone.