5:15 PM - 7:15 PM
[SCG62-P08] Large-strain deformation experiments of Davemaoite using rDAC and preliminary results of the relative strength of lower mantle minerals.
To understand the convection style of the lower mantle and the observed seismic anisotropy, it is crucial to investigate the rheological properties of its constituent minerals. The major minerals in the lower mantle are bridgmanite ((Mg,Fe)SiO3), ferropericlase ((Mg,Fe)O), and davemaoite (CaSiO3). While recent studies have improved our understanding of the strengths of bridgmanite and ferropericlase (e.g., Girard et al., 2016; Tsujino et al., 2022), our knowledge of davemaoite remains limited (Immoor et al., 2022). This is because of small volume ratio of davemaoite in the lower mantle minerals and it cannot be recovered at ambient pressure. In this study, we conducted ultra-high pressure torsional deformation experiments on davemaoite using a rotational diamond anvil cell (rDAC) combined with synchrotron X-rays at BL47XU, SPring-8. In this presentation, we report preliminary results on the strength contrast between davemaoite and periclase (Ishimori et al., under review).
Torsional deformation experiments on davemaoite were conducted using a combination of rDAC and synchrotron X-ray. Davemaoite was synthesized from wollastonite inside the rDAC by pressurizing and heating, using near-infrared heating (Azuma et al., 2024) and laser heating on the beamline. Subsequently, torsional deformation was applied to the sample by rotating the upper anvil of the rDAC (35 GPa, 893 K). During the deformation experiment, in-situ X-ray diffraction (XRD) measurements were performed to obtain Debye-Scherrer rings (Debye rings). From the obtained Debye rings, the d-spacing of davemaoite at each azimuthal angle was determined, and the differential stress were calculated (Park et al., 2022). In this stress analysis, we used the peaks of {110} plane of davemaoite.
From the one-dimensional XRD pattern, we observed the amorphization of the starting material progressed during pressurization, and the peaks of davemaoite appeared after subsequent heating. Stress data obtained from the {110} plane of davemaoite during deformation experiments suggest a transition from elastic to plastic deformation and reached a steady state. A comparison of our results for davemaoite with the stress data of periclase suggests that davemaoite has higher strength than periclase (Ishimori et al., under review). Although further detailed experiments and considerations are necessary, our results contradict the previous study by Immoor et al. (2022), which reported that periclase has higher strength than davemaoite.
Torsional deformation experiments on davemaoite were conducted using a combination of rDAC and synchrotron X-ray. Davemaoite was synthesized from wollastonite inside the rDAC by pressurizing and heating, using near-infrared heating (Azuma et al., 2024) and laser heating on the beamline. Subsequently, torsional deformation was applied to the sample by rotating the upper anvil of the rDAC (35 GPa, 893 K). During the deformation experiment, in-situ X-ray diffraction (XRD) measurements were performed to obtain Debye-Scherrer rings (Debye rings). From the obtained Debye rings, the d-spacing of davemaoite at each azimuthal angle was determined, and the differential stress were calculated (Park et al., 2022). In this stress analysis, we used the peaks of {110} plane of davemaoite.
From the one-dimensional XRD pattern, we observed the amorphization of the starting material progressed during pressurization, and the peaks of davemaoite appeared after subsequent heating. Stress data obtained from the {110} plane of davemaoite during deformation experiments suggest a transition from elastic to plastic deformation and reached a steady state. A comparison of our results for davemaoite with the stress data of periclase suggests that davemaoite has higher strength than periclase (Ishimori et al., under review). Although further detailed experiments and considerations are necessary, our results contradict the previous study by Immoor et al. (2022), which reported that periclase has higher strength than davemaoite.