Fission Track Annealing and Fission Track Age-Temperature Relationship in Sphene

Annealing characteristics of spontaneous (fossil) and induced (recent) fission tracks in sphene were measured in a temperature range of 873 to 768 K. Results include the reduction of number density, maximum track length (horizontal projection), and average track length (horizontal projection) as a function of annealing time [up to 1.5-10⁷ s (175 days)]. Using the track dimension method, a corrected fission track age for sphene was derived. The annealing characteristics are interpreted by means of a new annealing model, yielding information about the elementary processes governing the annealing mechanism for the etchable zone of fission tracks. Monomolec-ular recombination and the annealing of dislocation loops are proposed as the likely dominant annealing processes. Annealing coefficients α(T) obtained from the number density annealing characteristics under the assumption of a single exponential function approximation are used to derive an age-temperature relationship giving for a measured corrected fission track age in sphene the corresponding temperature . This age-temperature relationship of sphene is compared with the age-temperature relationship of apatite.