Polished slabs of zircon, oriented normal or parallel to c, were implanted with 100keV 3He to a dose of 5 x 1015/cm2. The 3He distributions were measured via nuclear reaction analysis using  3He(d,p)4He. For zircon, the Arrhenius relationship was:

D⊥c(m2/s) = 2.3 x 10-7exp[-146(kJ/mol)/RT]

D∥c(m2/s) = 1.7 x 10-5exp[-148(kJ/mol)/RT]

Although the activation energies for diffusion normal to and parallel to c were comparable, there was a marked diffusional anisotropy, with diffusion parallel to c being nearly 2 orders of magnitude faster than transport normal to c.

D.J.Cherniak, E.B.Watson, J.B.Thomas: Chemical Geology, 2009, 268[1-2], 155-66