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Micro‐Raman spectroscopy and SEM/EDX applied to improve the zircon fission track method used for dating geological formations
Author(s) -
Dias Airton Natanael Coelho,
Tello Saenz Carlos Alberto,
Constantino Carlos José Leopoldo,
Soares Cleber José,
Novaes Felipe Ponciano,
Balan Ana Maria Osório Araya
Publication year - 2009
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2088
Subject(s) - zircon , fission track dating , raman spectroscopy , scanning electron microscope , analytical chemistry (journal) , mineralogy , isotropic etching , geology , fission , anisotropy , etching (microfabrication) , amorphous solid , materials science , crystallography , chemistry , nanotechnology , optics , geochemistry , composite material , nuclear physics , physics , chromatography , layer (electronics) , neutron
The zircon mineral is widely studied in geochronology. In the case of the fission track method (FTM), the age is determined by the density of fission tracks at the zircon surface, which can be observed with an optical microscope after an appropriate chemical treatment (etching). The etching must be isotropic at the zircon grain surface to be used in the FTM, which leads those zircon grains whose etching is anisotropic to be discarded. The only reason for this discarding is the nonuniform morphology of the surface grain seen by optical microscopy, that is, no further physicochemical analysis is performed. In this work, combining micro‐Raman and scanning electron microscopy (SEM) to study the etching anisotropy, it was shown that zircon grains that present at least one area at the surface where the density of fission track is uniform can be used in the FTM. The micro‐Raman showed characteristic spectra of the standard zircon sample either from the areas where there are tracks or from where there are not. The only difference found was in the Raman bandwidths, which were broader for the areas with higher density of fission tracks. This suggests simply a decrease in the relative percentage of the crystalline/amorphous phases at these areas. The SEM/energy dispersive spectrometry (EDX) showed that there were no significant differences in the principal chemical composition at the areas with and without fission tracks. Copyright © 2008 John Wiley & Sons, Ltd.