Metamict zircon crystals have been thermally annealed between 500 and 1800 K and analyzed\ud
using infrared and optical spectroscopy in the spectral region of 1400–7000 cm–1. Recrystallization\ud
and dehydroxylation via complex proton/OH diffusion, redistribution, and incorporations of additional\ud
hydrogen-related species within the crystal structure of zircon occur at temperatures above 700 K\ud
in partially metamict zircon and above 1200 K in heavily amorphized material. Thermally induced\ud
changes in O-H stretching spectra are different between E || c and E ⊥ c in weakly metamict zircon. The\ud
O-H stretching band near 3342 cm–1 (with E ⊥ c) in an untreated sample shifts to 3277 cm–1 at 1200 K,\ud
where the frequency of O-H stretching bands with E || c increases. Conversions of hydrogen-related\ud
species were observed and extra OH bands were found at temperatures between 1200 and 1600 K. A\ud
dramatic change of OH spectra was recorded between 1600 and 1800 K in partially metamict crystals,\ud
resulting in additional absorption features (near 3098 and 2998 cm–1 along E ⊥ c). U4+ and U5+ related\ud
spectra are also affected by high-temperature annealing. For highly metamict zircon, the U4+ band\ud
near 4830 cm–1 shows an increase in intensity above 1200 K. Additional IR bands at 2146 and 2344\ud
cm–1 appear in the spectra of metamict zircon annealed at high temperatures. Their frequencies are\ud
consistent with stretching vibrations of CO and CO2
