A natural quartz sample was irradiated using a 200MeV proton beam in order to produce spallogenic 21Ne. Its temperature-dependent diffusivity was then determined by means of high-precision stepped heating and noble-gas mass spectrometry. The outward mobility of the proton-induced species reflected diffusion through the quartz lattice. The diffusion parameters were 153.7kJ/mol and ln(Do/a2) = 15.9ln[/s] for proton-induced 21Ne. The Ne diffusion parameters also indicated that diffusive loss had to be considered for small (<1mm) quartz grains that had experienced high temperatures. A roughly 70kJ/mol higher activation energy for Ne diffusion, as compared with He diffusion, was suggested to reflect an energy barrier related to its 13% greater diameter.

Diffusion Kinetics of Proton-Induced 21Ne, 3He and 4He in Quartz. D.L.Shuster, K.A.Farley: Geochimica et Cosmochimica Acta, 2005, 69[9], 2349-59