HR: 16:45h
AN: MR34A-04    [Abstracts]
TI: In-situ Laser Heating and Pressure Change With Radial Diffraction to Investigate Deformation of Deep Earth Relevant Minerals
AU: * Miyagi, L
EM: miyagi@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California Berkeley, 307 McCone hall, Berkeley, CA 94720, United States
AU: Kunz, M
EM: MKunz@lbl.gov
AF: Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, United States
AU: Voltolini, M
EM: voltolini@berkeley.edu
AF: Department of Earth and Planetary Science, University of California Berkeley, 307 McCone hall, Berkeley, CA 94720, United States
AU: Wenk, H
EM: wenk@berkeley.edu
AF: Department of Earth and Planetary Science, University of California Berkeley, 307 McCone hall, Berkeley, CA 94720, United States
AB: Abstract: Many deep Earth mineral phases have stability fields that are accessible only with diamond anvil cell (DAC), and currently this remains the only method for studying these mineral phases at pressures relevant to the deep Earth. So far radial diffraction DAC experiments have had two serious limitations, pressure and stress could only be applied incrementally ex-situ and deformation was limited to ambient temperature. These limitations bring into question the applicability of these experiments to deformation behavior in the deep earth where minerals are deforming at high-temperature and pressure. To address this issue we developed a novel combination of remotely controlled radial DAC with in-situ laser heating. This enables us to change pressure and thus stress on the sample while at high temperature. For remotely controlling the pressure we constructed a holding frame which can be used for different radial cell designs. The DAC is placed within the holding frame together with a gas-driven membrane. Inflating the membrane pushes the piston into the cylinder which is retained by the frame. While the membrane applies force from the bottom, the top of the assembly provides optical access for one- sided laser heating. The laser is directed from the top, vertically along the symmetry axis of the DAC onto the sample. The gas-pressure can be controlled remotely from outside the hutch, thus allowing for pressure change during heating and X-ray exposure. Using in-situ laser heating we induce recrystallization in a sample of Mg_0.75Fe_0.25O that had been deformed at room temperature. We observe grain growth and texture strengthening upon recrystallization. The remote pressure control is used to deform bcc Fe into the hcp Fe stability field and then back into the bcc phase on decompression. We observe development of strong textures in both the bcc phase and the hcp phase of Fe as well as texture change during decompression of the hcp phase. By combining the techniques, we convert in-situ a sample of natural San Carlos olivine (Fo_90.7Fa_9.3) into an assemblage of perovskite and periclase in the DAC. This sample was deformed at pressures from 30 to 50 GPa and at a temperature of 1100 ± 100 K. Both perovskite and periclase develop texture during deformation with periclase developing the stronger texture of the two. Texture in periclase is different from that obtained in room temperature compression experiments and this could be due to deformation in a two phase aggregate or deformation at high temperature. Elastic lattice strains are significantly lower in the perovskite and periclase assemblage when deformed at high temperature as compared to a room temperature experiment.
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
DE: 5120 Plasticity, diffusion, and creep
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting