Advances on microLIBS and microXRF mineralogical and elemental quantitative imaging

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 mu LIBS (micro Laser-Induced Breakdown Spectroscopy) and mu XRF (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 (similar to 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, mu LIBS and mu XRF quantitative elemental mapping are obtained using EPMA spot analyses as internal reference compositions. We exhibit the precision of the mu LIBS and mu XRF 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...).

Automated summary

This article introduces analytical methods for determining the distribution of elements in geological samples and discusses the advantages of mu LIBS and mu XRF techniques. By applying these methods to a mica schist thin section, the accuracy of major and trace element imaging is demonstrated, as well as the ability to differentiate minerals in more complex rock matrices.