Elasticity of a Pseudoproper Ferroelastic Transition from Stishovite to Post-Stishovite at High Pressure

Elasticity of Hydrated Al‐Bearing Stishovite and Post‐Stishovite: Implications for Understanding Regional Seismic VS Anomalies Along Subducting Slabs in the Lower Mantle

“…Additionally, the $${C}_{ij0}^{0}$$ can be calculated from literature C ij 0 data of stishovite at ambient conditions after taking into account of the linear Al effect on the C ij 0 in stishovite (Lakshtanov et al., 2007a). Since the pressure‐dependent slopes for Raman shifts and lattice parameters are very similar in Al,H‐bearing and pure SiO 2 stishovite (Figures 2c, 3c, and 3d), the $${C}_{ij}^{0}$$ slope, the pressure derivatives of $${C}_{ij}^{0}$$ ($${C}_{ij}^{0\prime }$$), of the experimentally‐determined values for pure SiO 2 endmember in a recent study can be used for the Al,H‐bearing stishovite (Zhang et al., 2021). The exception here is for the $${C}_{11}^{0\prime }$$ and $${C}_{12}^{0\prime }$$ that can be affected by the shear softening and the transition pressure such that these two parameters for the Al,H‐bearing stishovite need to be evaluated in the modeling.…”

“…The mineralogy in the selected MORB composition contains 20 vol% stishovite, 30 vol% CF, 30 vol% Bgm, and 20 vol% CaPv in the lower mantle (Ishii et al, 2019). Thermoelastic parameters of these mineral phases, except CaPv, in our modeling are taken from this study, Zhang et al (2021), andXu et al (2008). We should note that Xu et al (2008) determined these parameters using previous elasticity data at high P-T (refer to Table S10 in Supporting Information S1 for details; Akaogi et al, 1999;Fei & Ahrens, 1995;Fiquet et al, 2000;Funamori et al, 1998;Kiefer et al, 2002;Liu et al, 1999;Murakami et al, 2003;Shim & Duffy, 2000;Sinogeikin et al, 2004;Smyth & McCormick, 1995;Wentzcovitch et al, 2004).…”

“…2a and 2c). Literature results are also shown for comparison (Andrault et al, 2003;Bolfan-Casanova et al, 2009;Buchen et al, 2018;Lakshtanov et al, 2007b;Zhang et al, 2021). (b) Post-stishovite transition at high P-T conditions.…”

“…Although full elasticity of pure stishovite and post‐stishovite and the effect of Al on the post‐stishovite transition pressure have been relatively well investigated (Asahara et al., 2013; Karki et al., 1997; Lakshtanov et al., 2007b; Li et al., 1996; Shieh et al., 2002; Yang & Wu, 2014; Zhang et al., 2021), elasticity data of hydrated Al‐bearing stishovite across the post‐stishovite transition remain largely unexplored (Bolfan‐Casanova et al., 2009; Gréaux et al., 2016; Lakshtanov et al., 2007a). This is mainly due to the technical difficulty in measuring sound velocities and reliably deriving full elastic moduli ( C ij ) of the stishovite crystal at high pressure (Zhang et al., 2021). Alternatively, high‐pressure experimental results on Raman shifts of optic modes and equations of state (EOS) parameters across the post‐stishovite transition can be used to evaluate full C ij using Landau theory modeling (Carpenter et al., 2000).…”

Single-crystal elasticity of phase Egg AlSiO3OH and δ-AlOOH by Brillouin spectroscopy

“…Brillouin scattering measurements were conducted under ambient conditions using a Brillouin Light Scattering (BLS) system at the Mineral Physics Laboratory, the University of Texas at Austin(Fu et al 2017; Fu et al 2019;Zhang et al 2021). In the BLS system, a single-frequency 532 nm solid-state green laser (Coherent Verdi V2) was used as an excitation light source and a JRS six-pass tandem Fabry-Pérot interferometer equipped with a Perkin-Elmer photomultiplier detector was used to record the Brillouin spectra of the sample.…”