Role of Elastic Anisotropy in the Development of Deformation Microstructures in Zircon

Nicholas E. Timms, David Healy, Timmons M. Erickson, Alexander Nemchin, Mark A. Pearce, Aaron J. Cavosie

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

he deformation of zircon by various mechanisms, including brittle fracture, dislocation creep, twinning, and transformation to a high-pressure polymorph (reidite), is preceded by elastic behavior. This study presents new visualizations of the anisotropy of elastic properties of zircon as a function of radiation damage and pressure, and investigates the links between elastic properties and deformation microstructures in zircon. Zircon is highly anisotropic in Young's modulus (E), shear modulus (G), and Poisson's ratio (ν) elasticity. Anisotropy of E, G, and ν decreases by radiation damage and increases with pressure from 0 to 24 GPa, with a peak in elastic stiffness at ~8 GPa. A switch in dislocation line energy factor K could indicate that (001)<100>dislocations are energetically more favorable than {100}<010> above ~17 GPa. Shock twinning of zircon occurs via plane of invariant shear K 1 = {112} and shear direction η 1 = <111>, which corresponds to the lowest values of G <111> (~98 GPa) and ν(≈0) in zircon. Minima in G <111> at ~4 and ~16 GPa could indicate favorable pressures for twinning. Reduction of E and G associated with radiation damage inhibits propagation of reidite lamellae during shock metamorphism because sufficient pressures to permit phase transformation cannot be supported.
Original languageEnglish
Title of host publicationMicrostructural Geochronology
Subtitle of host publicationPlanetary Records Down to Atom Scale
EditorsDesmond E. Moser, Fernando Corfu, James R. Darling, Steven M. Reddy, Kimberly Tait
PublisherWiley
Pages183-202
Number of pages20
ISBN (Electronic)9781119227250
ISBN (Print)9781119227243
DOIs
Publication statusPublished - 29 Jan 2018

Publication series

NameGeophysical Monograph Series
PublisherAmerican Geophysical Union
Volume232
ISSN (Print)0065-8448

Keywords

  • deformation mechanism
  • zircon
  • shock
  • reidite
  • twin mode
  • EBSD

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    Timms, N. E., Healy, D., Erickson, T. M., Nemchin, A., Pearce, M. A., & Cavosie, A. J. (2018). Role of Elastic Anisotropy in the Development of Deformation Microstructures in Zircon. In D. E. Moser, F. Corfu, J. R. Darling, S. M. Reddy, & K. Tait (Eds.), Microstructural Geochronology: Planetary Records Down to Atom Scale (pp. 183-202). (Geophysical Monograph Series; Vol. 232). Wiley. https://doi.org/10.1002/9781119227250.ch8