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Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study

Author:
  • Andrius Rimsa
  • Nij. Whitehouse
  • Leif Johansson
  • S. Piazolo
Publishing year: 2007
Language: English
Pages: 1213-1224
Publication/Series: American Mineralogist
Volume: 92
Issue: 7
Document type: Journal article
Publisher: Mineralogical Society of America

Abstract english

The entire population of magmatic oscillatory zoned zircons in a migmatitic granite from the Tjarnesjo intrusion, southwest Sweden, reveal fine-scale brittle fracturing. The oscillatory zoned fragments are rotated but not dispersed. Fractures between individual fragments are sealed by newly formed CL-bright zircon. Hydraulic fracturing is the most probable mechanism. The internal structure of fractured zircons and the LREE-enriched, low Th character of CL-bright zircon both suggest that cracks between oscillatory zoned zircon fragments were rapidly sealed after fracturing by CL-bright zircon, precipitated from hydrothermal fluids. Zircon fracturing and crack-sealing has been dated by SIMS ion-probe and U-Th-Pb isotopes to 920 +/- 51 Ma (lower intercept age, 2 sigma, MSWD = 1.09) with a limit for the Youngest possible age of 960 +/- 16 Ma (Pb-207/(206) Pb, 2 sigma, MSWD = 0.23) dated by sector-zoned rims forming overgrowths on the fractured cores.

Keywords

  • Geology
  • hydraulic
  • sveconorwegian
  • U-Pb
  • cathodoluminescence
  • zircon
  • hydrothermal
  • fracturing
  • EBSD
  • SIMS

Other

Published
  • ISSN: 0003-004X
Leif Johansson
E-mail: leif [dot] johansson [at] geol [dot] lu [dot] se

Professor

Lithosphere and Biosphere Science

+46 46 222 98 87

+46 70 530 76 73

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