The rheological and transport properties of deep mantle materials

• Main Author: McCormack, R. J.
• Published: University College London (University of London) 2012
• Subjects: 550
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625735

This Ph.D. project was an experimental study of the rheological and transport properties of deep earth materials. It was conducted using high pressure and high temperature experiments on analogue phases and systems. Much of the research was focused on the D’’ region of the lower mantle and in particular on the post-perovskite phase present in that region. Analogue materials were used as the post-perovskite present in the lower mantle, MgSiO3, is not stable at conditions experimentally accessible with multi-anvil devices. Measurement of rheological properties of post-perovskite analogue phases was mostly performed using the d-Dia apparatus, which is a multi-anvil deformation device. These studies included the deformation of the CaPtO3 post-perovskite phase under pure shear; relative strength measurements of the perovskite and post-perovskite phases of CaIrO3 under simple shear and relative strength measurements of the NaCoF3 perovskite and post-perovskite phases under pure shear. Studies of the transport properties of deep earth materials were also undertaken. One such study focused on the anisotropy of diffusion of major ions in the post-perovskite structure. It was undertaken using inter-diffusion of Ir and Pt ions in CaIrO3 single crystals at high pressure and temperature. Another study investigated the possibility of the Reynolds’ dilatancy effect operating in the lower mantle. This study was conducted using the d-Dia apparatus and the imaging capabilities at a synchrotron light source. The final part of the project was the development of the new high pressure apparatus, the DT-Cup. This will allow future deformation experiments to be conducted at higher pressures than are currently accessible using multi-anvil devices. This will increase the range of post-perovskite analogue materials whose rheological properties can be quantitatively studied.