Aluminum diffusion in zircon

Al diffusion under anhydrous 1-atm conditions has been measured in natural zircon. Experiments used a source consisting of AlPO4-ZrSiO4 powder mixtures. were run air crimped Pt capsules. profiles with Nuclear Reaction Analysis (NRA) using the reaction 27Al(p, γ)28Si. For parallel to c, following Arrhenius relation is determined: D = 6.24 × 103 exp.(−774 ± 34 kJ mol−1 /RT) m2s−1 Diffusivities normal and c are similar, indicating little anisotropy Al. diffuses more rapidly than tetravalent cations that substitute on Si site zircon, but slowly trivalent substituting Zr site. These slow diffusivities indicate chemical signatures will be quite resistant diffusional alteration. example, compositions at center 50 μm radius zircon grains would preserved over times greater age earth temperatures excess 1000 °C.