摘要：Graphical abstractDisplay OmittedHighlights•Talc is one of the most elastically anisotropic minerals in subduction zone settings.•Talc-bearing lithology can readily explain ultra-slow velocity, highVP/VSratio, and large delay time.•Pressure dependence of the components of the elastic constant tensor exhibits anomalous behavior.AbstractTalc 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 usingfirst principlessimulations based on density functional theory corrected for dispersive forces. Our results indicate that principal components of the full elastic constant tensor C11and 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 highVP/VSratio, thus making it a potential candidate mineral phase that could readily explain unusually highVP/VSratio and large shear wave splitting delays as observed from seismological studies in many subduction systems.
关键词：KeywordsenTalcElasticitySeismic anisotropyHydrous mineralsSubduction zone
