Quantitative Imaging of Stable Isotopes by Ion Microprobe |
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Authors: | Jé rô me Alé on,Marc Chaussidon,Michel Champenois,Denis Mangin |
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Affiliation: | Centre de Recherches Pétrographiques et Géochimiques, CNRS, 15 rue Notre Dame des Pauvres, B.P. 20, 54501 Vandoeuvre-lès-Nancy, France |
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Abstract: | A new analytical procedure has been developed to measure oxygen isotopic ratios and, more generally, stable isotopic ratios in microparticles with a few % precision. This procedure uses ion microprobe quantitative imaging with a scanning microbeam. In this mode, ion images are acquired on the electron multiplier. Image processing allows extraction of areas of interest from the whole image and computation of isotopic ratios in the selected areas. The accuracy of this method has been tested for the analysis of the 18O/16O ratio in quartz and magnetite reference samples powdered to a grain size of 2-5 μm. A detailed study of the instrumental mass fractionation allowed an understanding of differences between classical spot analysis and scanning ion imaging, and showed that fractionation effects were related to grain topography for microparticle analysis, and to image processing or to secondary optical settings for ion imaging. The precision obtained for the measurement of ä18O was 3% for grains having a diameter of 2 μm. |
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Keywords: | ion microprobe imaging oxygen isotopes microparticles |
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