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

Summary, in 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.

• Författare: Andrius Rimsa; Nij. Whitehouse; Leif Johansson; S. Piazolo
• Avdelning/ar: Berggrundsgeologi
• Publiceringsår: 2007
• Språk: Engelska
• Sidor: 1213-1224
• Publikation/Tidskrift/Serie: American Mineralogist
• Volym: 92
• Issue: 7
• Länkar: http://dx.doi.org/10.2138/am.2007.2458
• Dokumenttyp: Artikel i tidskrift
• Förlag: Mineralogical Society of America
• Ämne: Geology
• Nyckelord: hydraulic; sveconorwegian; U-Pb; cathodoluminescence; zircon; hydrothermal; fracturing; EBSD; SIMS
• Status: Published
• ISBN/ISSN/Övrigt: ISSN: 0003-004X