Practical Aspects of X-Ray Mapping in Electron Probe Microanalysis of Minerals

X-ray element distribution maps acquired by wavelength-dispersive spectrometry (WDS) on electron probe microanalyzers (EPMA) are widely used to visualize small-scale spatial variations of the chemical composition in rocks and minerals. Often only qualitative x-ray intensity maps are presented where real compositional features are superimposed with instrumental artefacts such as x-ray continuum variations and spectral interferences. To provide reliable, quantitative information, WDS maps should be processed in the same way as point measurements in terms of background, interference and matrix corrections [1]. Natural perovskite (CaTiO 3 ) crystals from the Mark kimberlite (Lac De Gras, Canada) were mapped on a JEOL JXA-8530F Plus instrument at 15 kV accelerating voltage, beam current of 50 nA (Ca, Ti, Mg, Si, Fe, all K  ) or 300 nA (NaK  , NbL  , CeL  , NdL  , ThM  ), beam diameter of 0.2 µm, step size of 0.5 µm and dwell time of 200 ms. Oxygen was calculated by stoichiometry and the mean atomic number (MAN) background correction was employed [2]. They show complex oscillatory zoning with bands bright in BSE enriched in elements like Na and Th, or Nb, Ce, and Nd [3]. Fig. 1 shows the effect of background correction, quantification,