Arrhenius activation energy and transitivity in fission-track annealing equations

Fission-track annealing models aim to extrapolate laboratory annealing kinetics to the geological timescale for application to geological studies. Model trends empirically capture the mechanisms of track length reduction. To facilitate the interpretation of the fission-track annealing trends, a formalism, based on quantities already in use for the study of physicochemical processes, is developed and allows for the calculation of rate constants, Arrhenius activation energies, and transitivity functions for the fission-track annealing models. These quantities are then obtained for the parallel Arrhenius, parallel curvilinear, fanning Arrhenius, and fanning curvilinear models, and fitted with Durango apatite data. Parallel models showed to be consistent with a single activation energy mechanism and a reaction-order model of order approximate to - 4. However, the fanning curvilinear model is the one that results in better fits laboratory data and predictions in better agreement with geological evidence. Fanning models seem to describe a more complex picture, with concurrent recombination mechanisms presenting activation energies varying with time and temperature, and the reaction-order model seems not to be the most appropriate. It is apparent from the transitivity analysis that the dominant mechanisms described by the fanning models are classical (not quantum) energy barrier transitions.

Automated summary

Fission-track annealing models can be applied to geological studies to study physicochemical processes. Various models, such as parallel and fanning models, have been developed to describe track length reduction. The fanning curvilinear model fits laboratory data better and is more consistent with geological evidence, indicating that it provides a more accurate representation of the complex recombination mechanisms.