Hyperfine Interaction of Metamict Zircon Studied by PAC Spectroscopy

Zircon (ZrSiO4) is a common accessory mineral found in igneous and metamorphic rocks and is generally in an amorphous state due to self-irradiation from radioactive impurities. The crystalline structure may be recovered by annealing. We have studied the annealing behavior of a nearly fully metamict zircon specimen by perturbed angular correlation spectroscopy and powder X-ray diffraction. Our results are consistent with accepted damage accumulation models and point to a two-stage recovery process for the transition from metamict to crystalline zircon. In all of our experiments PAC overestimates the amorphous fraction as compared to that determined by diffraction experiments, and we propose an explanation for this discrepancy