GEOSCAN, résultats de la recherche


TitreOptimizing time step size for apatite fission track annealing models
AuteurIssler, D R
SourceComputers and Geosciences vol. 22, no. 1, 1996 p. 67-74,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 36794
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Sujetsantecedents thermiques; établissement de modèles; méthodes analytiques; traces de fission; sédimentologie; géomathématique
Résumé(disponible en anglais seulement)
Empirical isothermal apatite fission track (AFT) annealing models are used to extract variable temperature histories from measured AFT parameters by forward and inverse modeling techniques. Using one such published annealing model based on Durango apatite data, a method has been developed for optimally discretizing thermal histories into isothermal steps for the evaluation of the annealing model. The equation S=(square root log(TaTm)A1+A2e-(Tm-T)As-RA4 predicts isothermal time step size (S) as a function of maximum interval temperature (Tm in kelvins) and rate of temperature change (R in K m.y.-1) with constants A1 = 0.00596, A2 = 0.043, A3 = 34.8, and A4 = 0.978, and with the total annealing temperature (Ta) given as a power function of R, Ta = 398.15(R0.0157). This equation offers improved computational efficiency and accuracy for the full range of track length reduction in comparison with other methods published. Improved model performance is important particularly for inversion type models which may require the generation of thousands of model temperature histories with large variations in heating and cooling rates. For similar amounts of annealing, integration step sizes differ by two orders of magnitude for heating/cooling rates that range between 0.1 and 10 K m.y.-1, a range that encompasses most sedimentary basins. As an added advantage, users can specify the approximate degree of accuracy for track length calculations by multiplying S by the scaling factor, v10E, where E is the approximate percent error on calculated track lengths. For E values of 0.1 and 1.0, computed thermal histories are within <0.2 °C and <1.0 °C, respectively, of the true numerical solution.