Major Element Chemical Heterogeneity in Geo2 Olivine Micro-Beam Reference Material: A Spatial Approach to Quantifying Heterogeneity in Primary Reference Materials

A 270 spot-analysis study was conducted across a large (ca. 1200 μm x 1200 μm) chip of Geo2 olivine from a commercially available GEO Mk2 block (P and H Developments 2016) which revealed a 8.7% relative range in FeO abundance. Interleaved and overlapping grids of different resolutions were measured sequentially to prove spatial patterns are not due to drift or other external sources of error. Results were mapped and interpolated using commercially available geographical information system software, such that composition could be predicted according to location with high accuracy. The simple, systematic zonation pattern observed demonstrates that useful-sized regions of acceptable homogeneity do exist for some elements. This knowledge allows a user to target individual regions of a characterised chip for use as distinct measurement standards. As analysis times decrease and datasets grow, this approach may maximise laboratory efficiency by characterising large chips and extending time between standard block re-polish and coating, particularly in those cases where the avoidance of prior beam damage is a key concern.