Self-diffusion of Si under anhydrous conditions at 1atm was measured in natural zircon. The source of diffusant was a mixture of ZrO2 and 30Si-enriched SiO2 in 1:1 molar proportions. The 30Si profiles were measured using Rutherford back-scattering spectrometry and nuclear reaction analysis with the reaction 30Si

(p,γ)31P. For Si diffusion normal to c at 1350 to 1550C, the Arrhenius relationship was:

D(m2/s) = 5.8 exp[-702(kJ/mol)/RT]

According to the nuclear reaction analysis measurements. This agreed with the Arrhenius relationship determined using Rutherford back-scattering spectrometry measurements:

D(m2/s) = 62 exp[-738(kJ/mol)/RT]

Diffusion of Si parallel to c appeared to be  slightly faster.

D.J.Cherniak: Physics and Chemistry of Minerals, 2008, 35[4], 179-87