Elastic Anisotropy of Lizardite at Subduction Zone Conditions

Abstract

Subduction zones transport water into Earth's deep interior through slab subduction. Serpentine minerals, the primary hydration product of ultramafic peridotite, are abundant in most subduction zones. Characterization of their high‐temperature elasticity, particularly their anisotropy, will help us better estimate the extent of mantle serpentinization and the Earth's deep water cycle. Lizardite, the low‐temperature polymorph of serpentine, is stable under the P‐T conditions of cold subduction slabs (<260°C at 2 GPa), and its high‐temperature elasticity remains unknown. Here we report ab initio elasticity and acoustic wave velocities of lizardite at P‐T conditions of subduction zones. Our static results agree with previous studies. Its high‐temperature velocities are much higher than previous experimental‐based lizardite estimates with chrysotile but closer to antigorite velocities. The elastic anisotropy of lizardite is much larger than that of antigorite and could better account for the observed large shear‐wave splitting in some cold slabs such as Tonga.

Elasticity of Anhydrous Phase B Under Mantle Conditions: Implications for the Deep X‐Discontinuity in the Subduction Zones

“…This method only needs the VDos of the unstrained configuration to obtain high‐T elasticity, significantly reducing the computational workload to less than 10% of the conventional methods while maintaining high accuracy. This method has been applied successfully to many minerals (Deng et al., 2022, 2023; Duan et al., 2019; Hao et al., 2019; Z. J. Song et al., 2022; Wang et al., 2020; Wu & Wang, 2016; Zhao et al., 2022).…”

“…This method only needs the VDos of the unstrained configuration to obtain high-T elasticity, significantly reducing the computational workload to less than 10% of the conventional methods while maintaining high accuracy. This method has been applied successfully to many minerals (Deng et al, 2022(Deng et al, , 2023Duan et al, 2019;Hao et al, 2019;Wang et al, 2020;Wu & Wang, 2016;Zhao et al, 2022). Additionally, the phase boundary was determined by comparing the Gibbs free energy of the reactant and the product, which is directly deduced from F from…”

Elasticity of Phase H Under the Mantle Temperatures and Pressures: Implications for Discontinuities and Water Transport in the Mid‐Mantle

“…The method derives the analytical expression of the second derivative in Equation (1) and avoids the vibrational calculations of strained configurations. This method only requires one‐tenth of the computation workloads of the usual method without losing accuracy (e.g., Deng et al., 2022; Duan et al., 2019; Hao et al., 2019; Wang et al., 2020; Zhao et al., 2022; Zou et al., 2018).…”

Unveiling oxygen vacancy impact on lizardite thermo and mechanical properties

“…Subsequently, the softening in the c-axis direction was associated with the abrupt decay at 10 GPa of the elastic stiffness constants 18 . Very recently, Deng et al 9 presented a comprehensive DFT-based study on the lizardite elastic properties at P-T conditions of subduction zones, showing that lizardite has significant shear wave anisotropy and arguing that its large elastic anisotropy could result from the shear-wave splitting in the subducting slabs.…”