Fig. 1 The rotational Drickamer apparatus (RDA) cell assembly used to reach the shallow lower mantle conditions. (A) The anvils, gaskets, and cell assembly for the RDA deformation experiment; (B) a side view of the cell assembly; and (C) a top view of the cell assembly. Diffracted x-ray comes mostly from one side of a sample closer to the x-ray detectors.
Fig. 2 A plot of the equivalent stress in bridgmanite and magnesiowüstite as a function of strain. Run conditions are given in Table 1. Stress in bridgmanite was estimated by using diffraction peaks (110) and (112). Stress in magnesiowüstite was estimated by using diffraction peaks (200) and (220). In both cases, the stresses shown here are the arithmetic average of stresses estimated from these planes. Some hint of strain weakening can be seen, particularly for bridgmanite (hatched regions are drawn to guide the eyes). Results from beta 74 are based on estimated strain (strain marker was not visible). Also, the pressure and temperature conditions for beta 74 are different from all others. Bars represent the errors. Errors are given for one standard deviation and are due to the uncertainties in the peak shift and the fitting errors to equation S1 (supplementary materials).
Fig. 3 SEM (scanning electron microscope) back-scattering images of the recovered sample from the run gamma 21. (A) A back-scattered electron image of the RDA cell assembly cut along the diameter. The sample position, alumina ring, and TiC central electrode are labeled for clarity. The layers of material above the sample are also identified (ZrO2, Al2O3, TiC+Diamond, BN). (B) A back-scattered electron image of the recovered sample from the run gamma 21, deformed up to 100% strain. The light gray grains are mangesiowüstite, and the dark gray grains are bridgmanite. An oblate shape shows a strain ellipsoid corresponding to the bulk strain of 100%. Arrows indicate the sense of shear. (C) A back-scattered electron image of an undeformed sample from the run gamma 23. This sample was annealed at 27.4 GPa and 2140 K and quenched after 1.5 hours.
- Table 1 Summary of run conditions.
The total strain is the equivalent strain, εE, including both axial compression strain (εU) and shear strain (εS) as
.Run number Temperature
(K)Pressure
(GPa)Total strain
(%)Strain rate
(×10−5 s−1)beta 74* 2000 ± 100 24.1 ± 0.5 52 4.3 gamma 21* 2130 ± 100 27.0 ± 0.5 100 3.0 gamma 22 2130 ± 100 27.0 ± 0.5 55 ± 17 3.0 ± 0.9 gamma 23** 2140 ± 100 27.4 ± 0.5 0 0 gamma 24 2150 ± 100 27.5 ± 0.5 23 ± 7 3.2 ± 1.0 gamma 25 2150 ± 100 27.5 ± 0.5 48 ± 15 3.6 ± 1.1 *Strain marker was not visible in these runs. Strain was estimated from the angle of rotation of the anvil and the relationship between the angle of rotation and shear strain based on previous results. **After annealing, the furnace failed. No strain after annealing.
Supplementary Materials
www.sciencemag.org/content/351/6269/144/suppl/DC1
Materials and Methods
Figs. S1 to S5
References (28–41)
Database S1
Additional Files
- Shear deformation of bridgmanite and magnesiow??stite aggregates at lower mantle conditions
Jennifer Girard, George Amulele, Robert Farla, Anwar Mohiuddin, Shun-ichiro Karato
Materials/Methods, Supplementary Text, Tables, Figures, and/or References
- Materials and Methods
- Figs. S1 to S5
- References
Additional Data
