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Title: Isosymmetric pressure-induced bonding increase changes compression behavior of clinopyroxenes across jadeite-aegirine solid solution in subduction zones: ISOSYMMETRIC PHASE TRANSITION

Abstract

Pyroxenes are among the most important minerals of Earth's crust and upper mantle and play significant role in controlling subduction at convergent margins. In this study, synchrotron-based single-crystal X-ray diffraction experiments were carried out on a natural aegirine [NaFe 3+Si 2O 6] sample at ambient temperature and high pressures to 60 GPa, simulating conditions within the coldest part of a subduction zone consisting of old lithosphere. The diffraction data reveal no obvious sign of structural phase transition in aegirine within this pressure range; however, several relevant structural parameter trends change noticeably at approximately 24 GPa, indicating the presence of the previously predicted isosymmetric bonding change, related to increase of coordination number of Na + at M2 site. The pressure-volume data, fit with third-order Birch-Murnaghan (BM3) equation of state over the whole pressure range, yields K T0 = 126(2) GPa and K' T0 = 3.3(1), while separate BM3 fits performed for the 0–24.0 GPa and 29.9–60.4 GPa pressure ranges give K T0 = 118(3) GPa, K' T0 = 4.2(3) and K T0 = 133(2) GPa, K' T0 = 3.0(1), suggesting that the structure stiffens as a result of the new bond formation. Aegirine exhibits strong anisotropic compression with unit strain axialmore » ratios ε1:ε2:ε3 = 1.00:2.44:1.64. Structural refinements reveal that NaO 8 polyhedron is the most compressible and SiO 4 tetrahedron has the lowest compressibility. The consequence of bonding transition is that the compressional behavior of aegirine below ~24 GPa and above that pressure is quite different, with likely consequences for relevant thermodynamic parameters and ion diffusion coefficients.« less

Authors:
 [1]; ORCiD logo [2];  [3];  [4]; ORCiD logo [2]; ORCiD logo [2]
  1. Key Laboratory of High Temperature and High Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang China; Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu Hawaii USA; University of Chinese Academy of Sciences, Beijing China
  2. Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu Hawaii USA
  3. Key Laboratory of High Temperature and High Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang China
  4. Department of Geosciences, University of Arizona, Tucson Arizona USA
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Science Foundation (NSF)
OSTI Identifier:
1355027
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research. Solid Earth; Journal Volume: 122; Journal Issue: 1
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES

Citation Formats

Xu, Jingui, Zhang, Dongzhou, Fan, Dawei, Downs, Robert T., Hu, Yi, and Dera, Przemyslaw K. Isosymmetric pressure-induced bonding increase changes compression behavior of clinopyroxenes across jadeite-aegirine solid solution in subduction zones: ISOSYMMETRIC PHASE TRANSITION. United States: N. p., 2017. Web. doi:10.1002/2016JB013502.
Xu, Jingui, Zhang, Dongzhou, Fan, Dawei, Downs, Robert T., Hu, Yi, & Dera, Przemyslaw K. Isosymmetric pressure-induced bonding increase changes compression behavior of clinopyroxenes across jadeite-aegirine solid solution in subduction zones: ISOSYMMETRIC PHASE TRANSITION. United States. doi:10.1002/2016JB013502.
Xu, Jingui, Zhang, Dongzhou, Fan, Dawei, Downs, Robert T., Hu, Yi, and Dera, Przemyslaw K. Sun . "Isosymmetric pressure-induced bonding increase changes compression behavior of clinopyroxenes across jadeite-aegirine solid solution in subduction zones: ISOSYMMETRIC PHASE TRANSITION". United States. doi:10.1002/2016JB013502.
@article{osti_1355027,
title = {Isosymmetric pressure-induced bonding increase changes compression behavior of clinopyroxenes across jadeite-aegirine solid solution in subduction zones: ISOSYMMETRIC PHASE TRANSITION},
author = {Xu, Jingui and Zhang, Dongzhou and Fan, Dawei and Downs, Robert T. and Hu, Yi and Dera, Przemyslaw K.},
abstractNote = {Pyroxenes are among the most important minerals of Earth's crust and upper mantle and play significant role in controlling subduction at convergent margins. In this study, synchrotron-based single-crystal X-ray diffraction experiments were carried out on a natural aegirine [NaFe3+Si2O6] sample at ambient temperature and high pressures to 60 GPa, simulating conditions within the coldest part of a subduction zone consisting of old lithosphere. The diffraction data reveal no obvious sign of structural phase transition in aegirine within this pressure range; however, several relevant structural parameter trends change noticeably at approximately 24 GPa, indicating the presence of the previously predicted isosymmetric bonding change, related to increase of coordination number of Na+ at M2 site. The pressure-volume data, fit with third-order Birch-Murnaghan (BM3) equation of state over the whole pressure range, yields KT0 = 126(2) GPa and K'T0 = 3.3(1), while separate BM3 fits performed for the 0–24.0 GPa and 29.9–60.4 GPa pressure ranges give KT0 = 118(3) GPa, K'T0 = 4.2(3) and KT0 = 133(2) GPa, K'T0 = 3.0(1), suggesting that the structure stiffens as a result of the new bond formation. Aegirine exhibits strong anisotropic compression with unit strain axial ratios ε1:ε2:ε3 = 1.00:2.44:1.64. Structural refinements reveal that NaO8 polyhedron is the most compressible and SiO4 tetrahedron has the lowest compressibility. The consequence of bonding transition is that the compressional behavior of aegirine below ~24 GPa and above that pressure is quite different, with likely consequences for relevant thermodynamic parameters and ion diffusion coefficients.},
doi = {10.1002/2016JB013502},
journal = {Journal of Geophysical Research. Solid Earth},
number = 1,
volume = 122,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2017},
month = {Sun Jan 01 00:00:00 EST 2017}
}
  • The structural evolution of tetragonal Zr{sub 2}Cu has been investigated under high pressures up to 70 GPa by means of density functional theory. Our calculations predict a pressure-induced isosymmetric transition where the tetragonal symmetry (I4/mmm) is retained during the entire compression as well as decompression process while its axial ratio (c/a) undergoes a transition from ∼3.5 to ∼4.2 at around 35 GPa with a hysteresis width of about 4 GPa accompanied by an obvious volume collapse of 1.8% and anomalous elastic properties such as weak mechanical stability, dramatically high elastic anisotropy, and low Young's modulus. Crystallographically, the tetragonal axial ratiomore » shift renders this transition analogous to a simple bcc-to-fcc structural transition, which implies it might be densification-driven. Electronically, the ambient Zr{sub 2}Cu is uncovered with an intriguing pseudo BaFe{sub 2}As{sub 2}-type structure, which upon the phase transition undergoes an electron density topological change and collapses to an atomic-sandwich-like structure. The pseudo BaFe{sub 2}As{sub 2}-type structure is demonstrated to be shaped by hybridized dxz + yz electronic states below Fermi level, while the high pressure straight Zr-Zr bonding is accommodated by electronic states near Fermi level with dx{sup 2} − y{sup 2} dominant features.« less
  • A pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure was found in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fcc and themore » hcp phases for the three alloys are very small, but they are sensitive to temperature. The critical transition pressure in NiCoCrFe varies from ~1 GPa at room temperature to ~6 GPa at 500 K.« less
  • In this research, pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure wasfound in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~ 40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fccmore » and the hcp phases for the three alloys are very small, but they are sensitive to temperature. Finally, the critical transition pressure in NiCoCrFe varies from 1 GPa at room temperature to 6 GPa at 500 K.« less