Novos insights metodológicos para Traços de Fissão espontâneos em olivinas da Ilha das Flores, Arquipélago dos Açores, Portugal

Abstract

This work presents a study in Fission Tracks in olivines presents in the volcanic rocks of Flores Island, Azores Archipelago, Portugal. The study aims to promote the discussion about the applicability of the olivines in the thermochronological study by Fission Tracks, in a resumption and improvement of the methodology applied in the 1960s. For this purpose, the data base of this study was composed of rocks samples from the Volcanic Complexes (BC & UC) of Flores Island. The samples were treated and analyzed in different laboratories of the Federal University of Pampa (Unipampa) and Federal University of Rio Grande do Sul (UFRGS). The methodology of the study consisted of steps of petrographic description of the samples with the aid of transmitted light optical microscopy, scanning electron microscopy (SEM), and finally, the Fission Tracks Thermochronological Method, which includes steps such as: mineral disintegration, separation of olivines, assembly of pellets in epoxy resin and chemical attack to reveal the fission tracks. Four chemical attacks based on Potassium Hydroxide and Hydrochloric Acid (T1, T2, T3 and T4) were tested. There was a differentiation of olivine submission time for each attack. The results were very promising for the revelation of spontaneous tracks and understanding of the evolution and behavior of the traits as a function of the exposure time of olivines to attack chemical agents. Thus, the study contributed to the understanding and improvement of the methodology involved in the revelation of Fission Tracks in magmatic olivines and the study of olivines from Flores Island, Archipelago of the Azores-PT.