Recrystallisation and Trace-Element Mobility in Zircons: Implications for U-Pb Dating

Complex microstructures of zircon recrystallisation have been discovered in igneous and metamorphic zircons from the Jack Hills Metasedimentary Belt Western Australia, granitic injection complex Harris north-west Scotland. Cathodoluminescence (CL), electron backscatter diffraction (EBSD) wavelength dispersive spectroscopy (WDS) analysis reveal that studied is often characterised by (1) translation, bending fading oscillatory zoning; (2) structural recovery zircon; (3) an enrichment Hf depletion Y recrystallised (4) formation a interface with minor (<2°) misorientation. A new, composite model which trace element dislocation migration occurs shortly after crystallisation during magmatic cooling pipe diffusion along arrays formed accumulation dislocations allows enhanced to enrich leach U, Pb Y. After event, subsequent metamictization primary (typically zoning) creates zones can structurally recover through diffusion-reaction re-equilibration mechanism, resulting further trace-element mobility. These mechanisms create zircons, suggesting detailed understanding history may be required accurately interpret its U-Pb ages.