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

作　　者：Ye Peng Mainak Mookherjee Andreas Hermann Geeth Manthilake David Mainprice 

机构地区：[1]Earth Materials Laboratory,Department of Earth,Ocean,and Atmospheric Sciences,Florida State University,Tallahassee,FL 32306,USA [2]Centre for Science at Extreme Conditions and SUPA,School of Physics and Astronomy,The University of Edinburgh,Edinburgh EH93FD,UK [3]Laboratoire Magmas et Volcans CNRS,IRD,OPGC,UniversitéClermont Auvergne,63000 Clermont-Ferrand,France [4]Geosciences Montpellier,UMR CNRS 5243,Universitéde Montpellier,Montpellier 34095,France

出　　处：《Geoscience Frontiers》2022年第4期34-47,共14页地学前缘（英文版）

基　　金：supported by the US National Science Foundation grant EAR 1763215 and EAR 1753125;XSEDE facilities(GEO170003);the High-Performance Computing,Research Computing Center,Florida State University;the UK’s National Supercomputer Service through the UK CarParrinello Consortium(EPSRC Grant No.EP/P022561/1)and project ID d56"Planetary Interiors";funding from the INSU-CNRS;the French Government Laboratory of Excellence initiative n°ANR-10-LABX-0006,the Région Auvergne;the European Regional Development Fund(Cler Volc contribution number 530).

摘　　要：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 C_(11) and C_(22),shear components C_(66),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 V_(P)/V_(S) ratio,thus making it a potential candidate mineral phase that could readily explain unusually high V_(P)/V_(S) ratio and large shear wave splitting delays as observed from seismological studies in many subduction systems.

关 键 词：TALC ELASTICITY Seismic anisotropy Hydrous minerals Subduction zone 

分 类 号：P578.94[天文地球—矿物学]