Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Geophysics

Supervisor

Dr. Sean R. Shieh

Abstract

Zircon (ZrSiO4) is a strong accessory mineral that can retain U, Th and Hf within its structure. This makes zircon an important material in geochemical and geochronological studies. In addition, the strong thermal shock resistance of zircon allows for dating the formations of melt and impact events and to separate shocked and potentially shocked country rocks. However, the deformation mechanism and microstructure behavior of zircon at high pressure is poorly understood. Therefore, this work aims to study the deformation and texture of zircon in situ at high pressure and room temperature, and also to examine the microstructure of samples recovered from high pressure.

Angle-dispersive X-ray diffraction in a radial geometry using a diamond-anvil cell was performed at beamline X17C, National Synchrotron Light Source (NSLS). Volume data fitted to Birch-Murnaghan equation of state yielded a bulk modulus of 203±13 GPa (K0=4) at hydrostatic conditions, and also shown zircon is a strong but stress sensitive mineral. The differential stress supported by zircon is in the range of 2.5 – 5.5 GPa in this study. Differential stress supported by (200) plane exhibited as the weakest and deformed plastically above 18 GPa. Weak texture in (001) was observed at low pressure and rotated towards to (110) due to the applied stress. Twins with 650 misorientation were observed within the stability field of zircon in recovered sample. Both ‘parent’ and twined zones had residual strain up to 250.

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