The chemical diffusion of Ti under anhydrous conditions at 1atm and under fluid-present elevated pressure (1.1 to 1.2GPa) conditions was measured in natural zircon. The source of the diffusant for 1atm experiments was a ZrO2–TiO2–zircon mixture, with the experiments being run in crimped Pt capsules. Diffusion experiments performed in the presence of H2O–CO2 fluid were carried out in a piston-cylinder apparatus using a source of ground TiO2, ZrSiO4 and SiO2; with oxalic acid being added in order to produce H2O–CO2 vapor and partially melt the solid source material to yield the ensemble: rutile + zircon + melt + vapor. Nuclear reaction analysis, using the resonant nuclear reaction, 48Ti(p,γ)49V, was used to measure diffusion profiles for both sets of experiments. The Arrhenius behavior of normal Ti diffusion at 1350 to 1550C and 1atm was described by:

D (m2/s) = 3.33 x 102 exp[-754(kJ/mol)/RT]

The Ti diffusivities were found to be similar for experiments performed under fluid-present conditions. A fit to all of the data yielded the relationship:

D (m2/s) = 1.34 x 102 exp[-741(kJ/mol)/RT]

The Ti diffused somewhat faster in zircon than did the larger tetravalent cations, U, Th and Hf, but considerably more slowly than did Pb, rare-earth elements and O.

Ti Diffusion in Zircon. D.J.Cherniak, E.B.Watson: Chemical Geology, 2007, 242[3-4], 470-83