Roman spectroscopy of synthetic zircon : Effects of chemical composition

Raman spectra of zircon show a distinctive pattern according to the amount of stored radiation damage. Nasdala et al. (2001) demonstrated that a linear relationship exists between the full width at half-maximum (FWHM) of the ᴠ3(SiO₄) band, observed at ∼1000 cm⁻¹, and the alpha fluence calculated from the uranium content, thorium content and the zircon age. Their finding could lead to a new micro-spectroscopic method to determine zircon ages. This study examines the effect of chemical composition on Raman spectra by the analysis of synthetic zircons that were doped with elements using Li-Mo flux. Zircons were found to be able to incorporate high concentrations of group 3 elements (including lanthanides and actinides) while elements belonging to other groups were less incorporated. The FWHM of the group 3 doped zircon ᴠ3(SiO₄) band showed a linear relationship with concentration, clearly indicating that the FWHM is a function of chemical composition as well as of radiation damage. However, a very high concentration of group 3 elements is required to influence these Raman spectra (e.g., more than ∼5,000ppm).