Elasticity of superhydrous B

Elasticity of superhydrous phase B, seismic anomalies in cold slabs and implications for deep water transport

“…5 and 6. The room pressure pure compressional and shear single-crystal elastic moduli (C ii ) obtained in this study are in excellent agreement with those reported by Pacalo and Weidner (1996) ( Table 1). Differences that exceed mutual uncertainties are however observed in the off-diagonal C ij elastic constants, namely C 13 and C 23 that are respectively 10% and 8% lower than those of Pacalo and Weidner (1996).…”

“…The room pressure pure compressional and shear single-crystal elastic moduli (C ii ) obtained in this study are in excellent agreement with those reported by Pacalo and Weidner (1996) ( Table 1). Differences that exceed mutual uncertainties are however observed in the off-diagonal C ij elastic constants, namely C 13 and C 23 that are respectively 10% and 8% lower than those of Pacalo and Weidner (1996). Deviations can be likely explained by differences in the experimental approaches because all our measurements were conducted in platelet scattering geometry, which reduces the uncertainties associated to the refractive index of the sample and the internal scattering angle in the calculation of the phonon directions and acoustic velocities (Sinogeikin and Bass, 2000;Whitfield et al, 1976).…”

“…Deviations can be likely explained by differences in the experimental approaches because all our measurements were conducted in platelet scattering geometry, which reduces the uncertainties associated to the refractive index of the sample and the internal scattering angle in the calculation of the phonon directions and acoustic velocities (Sinogeikin and Bass, 2000;Whitfield et al, 1976). Moreover, a larger number of velocity modes than in the work of Pacalo and Weidner (1996) were measured in this study (82 vs. 57 velocity modes, Table 1). We note that the differences in the C ij have a minimal effect on the calculated aggregate elastic moduli and velocities, K S , l, V P and V S , that are in excellent agreement within mutual uncertainties ( Table 1).…”

“…The apexes of the silicon tetrahedra that are highly resistant to compression (Levien and Prewitt, 1981) are all aligned along the b-axis explaining the low compliance of the C 22 moduli. A more detailed description of the relationship between the crystal structure of ShyB and its elastic properties is presented in Pacalo and Weidner (1996) and Crichton et al (1999).…”

“…The pure compressional moduli, C 11 , C 22 and C 33 , can be related to the stiffest structural element when compressional (or tensile) stresses are applied along the crystallographic a-, b-and c-axis, respectively i.e., (Pacalo and Weidner, 1996). ShyB exhibits a small degree of elastic anisotropy at ambient pressure due to the moderate contrasts (maximal 10%) between the magnitudes of the compressional moduli C ii (with i = 1, 2, 3) that is maintained upon compression (Table 1).…”