Kinetic model for the annealing of fission tracks in minerals and its application to apatite

Autor(es)

Guedes‚ S. ; Hadler N‚ JC ; Oliveira‚ KMG ; Moreira‚ P. ; Iunes‚ PJ ; Tello S‚ CA

• Tipo de documento: Artigo Científico
• Fonte: Radiation Measurements; v. 41, n. 4, p. 392-398, 2006.

Resumo

Fission tracks are formed in apatite and other minerals after the passage of fission fragments, which deliver locally intense amounts of energy to the crystal lattice. It is well known that the observable mean track lengths are reduced due to thermal treatment. If the annealing kinetics are known, it is sometimes possible to infer the thermal history a given sample experienced. Given the present lack of appropriate information on track formation, annealing and etching, researchers have used empirical models fitted to laboratory data on annealing to describe the annealing kinetics. In this work, a kinetic model is presented to describe the annealing process. It is based upon some experimental evidence. Instead of furnishing a complete and detailed description, it is intended to relate the observable quantities, namely, etched confined fission tracks, time and temperature based on simple hypotheses using a simplified view of the track. A kinetic model equation for the reduced mean track length, L/L-0, as a function of temperature, T, and heating duration, t, which fits quite well the available literature, has been derived and is given by (L/L-0) =exp{-n exp[-w'(U-0 - A(1) In(t) + A(2) In-2 (t) - k(B)T)(1/2)]} in which n is a parameter related to etching and track geometry, w' and U-0 are the width and the energy of a newly hypothesized potential barrier, respectively. A(1) and A(2) account for the dependence of the energy barrier on the duration of heating. Correlations with cell parameters of compositionally different apatites show that the barrier energy is the principal model descriptor for annealing. (c) 2005 Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 01/02805-9 - Sistematização e aprimoramento da metodologia de traços de fissão e sua aplicação em apatita dentro do estudo termotectônico da Plataforma Sulamericana região sudeste brasileira
• Beneficiário: Sandro Guedes de Oliveira
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 00/03960-5 - História de exumação da plataforma sulamericana a exemplo da região sudeste brasileira: termocronologia por traços de fissão e sistemáticas ar/ar e sm/nd
• Beneficiário: Peter Christian Hackspacher
• Modalidade de apoio: Auxílio à Pesquisa - Temático