Quantitative mapping of geological samples by electron microprobe using mean atomic number (MAN) background corrections: method application, data processing and visualization.

Electron probe microanalysis (EPMA) and wavelength dispersive spectroscopy (WDS) are ubiquitous tools for chemical analysis of geological samples. Analysis type is often confined to quantitative but spatially-limited (∼0.5-2+ µm diameter) spot analysis, or qualitative but spatially-resolved mapping. This contribution outlines a method that combines the quantitative aspect of spot analyses with the spatial resolution of EPMA mapping and associated data processing and visualization workflows. The acquisition and processing of spatially-resolved, quantitative chemical maps of geological samples allows for systematic characterization of mineral composition and compositional variations across rock textures, determination of local or effective bulk rock compositions, and further application of texturally-informed thermobarometric calculations.•Application of the mean atomic number (MAN) background-correction routine for EPMA mapping yields efficient and accurate quantitative chemical maps of geological samples.•Data filtering workflows based on mineralogical identification and stoichiometry constraints yield meaningful mineral composition data.•Free and open-source geographic information systems (GIS) software provides a tool for data-visualization strategies to explore the multi-dimensionality of quantitative EPMA map data.