Quantification of oxygen isotope SIMS matrix effects in olivine samples: Correlation with sputter rate

We investigated the magnitude and reproducibility of instrumental mass-dependent fractionation of oxygen isotopes in secondary ion mass spectrometry (SIMS) analyses of olivine crystals of different major element chemistry (from Mg-rich to Fe-rich) in order to improve the accuracy of in-situ O-isotope measurements in geochemical/cosmochemical olivine samples. We found that oxygen isotope SIMS matrix effects are reproducible, and developed a model curve that can be used for correcting instrumental mass fractionation of olivine samples of intermediate chemical composition. The changes in instrumental mass fractionations were likely caused by differing Cs concentrations in the near surface regions of the samples due to different sample sputtering rates.