Advances on microLIBS and microXRF mineralogical and elemental quantitative imaging
Résumé
Mineralogical and petrographic studies require analytical methods capable to underline the repartition of major to trace elements within geological samples. The EPMA (Electron Probe Micro Analyzer) conventional method used for such investigation, but on restrictive zones, is on the verge to be reached by μLIBS (micro Laser-Induced Breakdown Spectroscopy) and μXRF (micro X-Ray Fluorescence) techniques allowing the elemental imaging on thin rock sections or even larger samples in only several hours. These spectroscopic methods with extremely fast acquisition speed (~10 ms/pixel) are perfectly adapted to perform multi-elemental imaging of major to trace elements down to the ppm-level. Here, on a mica schist thin section that displays a wide paragenesis of minerals, μLIBS and μXRF quantitative elemental mapping are obtained using EPMA spot analyses as internal reference compositions. We exhibit the precision of the μLIBS and μXRF quantitative elemental imaging for major and trace elements repartition in an entire thin/thick rock section. According to these oxide weight contents, a rapid mineral classification is obtained, with a good discrimination between minerals even for those with similar compositions (alumino-silicates such as andalusite and kyanite) and within a complex matrix (Fe-oxides, quartz, micas, feldspars…).