Estudo da datação por traços de fissão em epídoto

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Epidote is a mineral with promising applications in the Fission Tracks Method (FTM). Among them, can be stressed his formation in fault zones and his high closure temperature compared with the better studied mineral, the apatite. In the 1970´s, the fission-track community turned the attention to epidote but abandoned it in the next decade due to difficulties for its treatment. Some difficulties were: heterogeneous U distribution, innumerable imperfections inside the epidote grains and dependence of the track shapes with the crystallographic orientation of the etched surface. Besides, there are no agreement about the chemical etching used to reveal tracks on epidote. In this work, the epidote fission track methodology was got back and some changes were applied to it, intending to make the method applicable. During the track counting, wide density histograms were obtained, when all the tracks were counted. By analysing the track shapes, it was realized that some tracks were darker and oriented in a short angular distribution. The counting of tracks in this "fission-track window" yields closer Poisson distributions, what decrease the dating error. The dating of a monocrystal from Brejuí(Rio Grande do Norte) was carried out and yielded some interesting results. The obtained age, (551 ± 74) My, is compatible with results of other dating methods and is related to its formation age. A bimodal distribution of confined lengths of fossil fission tracks was found. The age related with one of the bimodal peaks, (368 ± 59) My, allows to access an event posterior to the crystal formation that has not a geological interpretation yet

ASSUNTO(S)

datação radiotiva - borborema (rn) metodo do detetor externo datação do traço de fissão epidoto

ACESSO AO ARTIGO

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