HR: 12:05h
AN: MR52A-08    [Abstracts]
TI: Transformational Weakening During the Perovskite-Post Perovskite Phase Transition in CaIrO3
AU: * Hunt, S A
EM: s.hunt@ucl.ac.uk
AF: Deparment of Earth Sciences, UCL, Gower Street, London, WC1E 6BT, United Kingdom
AU: Dobson, D P
EM: d.dobson@ucl.ac.uk
AF: Deparment of Earth Sciences, UCL, Gower Street, London, WC1E 6BT, United Kingdom
AU: Weidner, D J
EM: Donald.Weidner@sunysb.edu
AF: Department of Geoscience, Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794-2100, United States
AU: Li, L
EM: lilli@ic.sunysb.edu
AF: Department of Geoscience, Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794-2100, United States
AU: Vaughan, M T
EM: Michael.Vaughan@sunysb.edu
AF: Department of Geoscience, Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794-2100, United States
AU: Walte, N
EM: Nico.Walte@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Universitat Bayreuth, Stony Brook, NY D-95440, Germany
AU: Brodholt, J P
EM: j.brodholt@ucl.ac.uk
AF: Deparment of Earth Sciences, UCL, Gower Street, London, WC1E 6BT, United Kingdom
AB: The D" layer plays a fundamental role in core - mantle interactions. The recent discovery of a CaIrO₃ structured phase of MgSiO₃, the so called post-perovskite (ppv) phase, significantly altered our understanding of the seismic and dynamic properties of the D". Here we report results of a study of the rheology during transformation from pv to pvv. The experiments were performed using the D-DIA on the X17B2 beamline at NSLS. A sample of presintered perovskite structured CaIrO₃ was deformed, along with a MgO stress calibrant, during heating at 3 GPa and up to 1000°C in a 8mm D-DIA assembly. The stress was measured by X-ray diffraction from the MgO sample and a proxy for the phase proportions was the relative strengths of unique perovskite and post-perovskite diffraction peaks from the CaIrO₃ sample. The strain was measured by X-radiography, from the position of Platinum foils placed above, between and below the two samples. From this data the viscosity of the CaIrO₃ sample can be calculated as well as the progress of the reaction. During the transformation to post-perovskite we observed a two fold weakening of the pv and ppv mixture; followed by an increase in the strength of the mixture to greater than that of that starting perovskite-structured material. If MgSiO₃ behaves in the same way during pv - ppv transformation it will cause a viscous decoupling between the lower mantle and the D". This in turn has major implications for the topography that can be supported at the top of the D" layer.
DE: 3621 Mantle processes (1038)
DE: 3630 Experimental mineralogy and petrology
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting