Anomalous elasticity of talc at high pressures: Implications for subduction systems

Ye Peng*, Mainak Mookherjee, Andreas Hermann, Geeth Manthilake, David Mainprice

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Talc is a layered hydrous silicate mineral that plays a vital role in transporting water into Earth’s interior and is crucial for explaining geophysical observations in subduction zone settings. In this study, we explored the structure, equation of state, and elasticity of both triclinic and monoclinic talc under high pressures up to 18 GPa using first principles simulations based on density functional theory corrected for dispersive forces. Our results indicate that principal components of the full elastic constant tensor C11 and C22, shear components C66, and several off-diagonal components show anomalous pressure dependence. This non-monotonic pressure dependence of elastic constant components is likely related to the structural changes and is often manifested in a polytypic transition from a low-pressure polytype talc-I to a high-pressure polytype talc-II. The polytypic transition of talc occurs at pressures within its thermodynamic stability. However, the bulk and shear elastic moduli show no anomalous softening. Our study also shows that talc has low velocity, extremely high anisotropy, and anomalously high VP/VS ratio, thus making it a potential candidate mineral phase that could readily explain unusually high VP/VS ratio and large shear wave splitting delays as observed from seismological studies in many subduction systems.
Original languageEnglish
Article number101381
Pages (from-to)1-14
Number of pages14
JournalGeoscience Frontiers
Volume13
Issue number4
Early online date15 Mar 2022
DOIs
Publication statusPublished - 1 Apr 2022

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