Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6447568 | Physics of the Earth and Planetary Interiors | 2014 | 46 Pages |
Abstract
We investigated the response of the crystal structure, lattice parameters, and unit-cell volume of hydrous layered silicate phlogopite at conditions relevant to subduction zone settings. We have used first principles simulation based on density functional theory to calculate the equation of state and full elastic constant tensor. Based on the generalized gradient approximation, the full single crystal elastic constant tensor with monoclinic symmetry shows significant anisotropy with the compressional elastic constants: c11Â =Â 181Â GPa, c22Â =Â 185Â GPa, c33Â =Â 62Â GPa, the shear elastic constants c44Â =Â 14Â GPa, c55Â =Â 20Â GPa, c66Â =Â 68Â Ga, and c46Â =Â â6Â GPa; the off diagonal elastic constants c12Â =Â 48Â GPa, c13Â =Â 12Â GPa, c23Â =Â 12Â GPa, c15Â =Â â16Â GPa, c25Â =Â â5Â GPa and c35Â =Â â1Â GPa at zero pressure. The elastic anisotropy of phlogopite is larger than most of the layered hydrous phases relevant in the subduction zone conditions. The shear anisotropy, AVS for phlogopite is â¼77% at zero pressure condition and although it decreases upon compression it remains relatively high compared to other hydrous phases relevant in the subduction zone settings. We also note that the shear elastic constants for phlogopite are relatively low. Phlogopite also has a high isotropic bulk VP/VS ratio â¼2.0. However, the VP/VS ratio also exhibits significant anisotropy with values as low as 1.49. Thus, phlogopite bearing metasomatized mantle could readily explain unusual VP/VS ratio as observed from seismological studies from the mantle wedge regions of the subduction zone.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Tanvi D. Chheda, Mainak Mookherjee, David Mainprice, Antonio M. dos Santos, Jamie J. Molaison, Julien Chantel, Geeth Manthilake, William A. Bassett,