Inter‐laboratory Characterisation of Apatite Reference Materials for Oxygen Isotope Analysis and Associated Methodological Considerations

Here we report on the oxygen isotope compositions of four proposed apatite reference materials (chlorapatite MGMH#133648 and fluorapatite specimens MGMH#128441A, MZ-TH, ES-MM). The samples were initially screened for 18O/16O homogeneity using secondary ion mass spectrometry (SIMS) followed by δ18O determinations in six gas source ratio laboratories (GS-IRMS) employing a variety analytical protocols determining either phosphate-bonded or “bulk” compositions. We also preliminary δ17O Δ’17O data, major trace element collected EPMA as well CO32- OH- contents structure assessed thermogravimetric analysis infrared spectroscopy. repeatability our SIMS measurements was better than ± 0.25 ‰ (1s) all that cover wide range 103δ18O values between +5.8 +21.7. GS-IRMS results show, however, significant offset “phosphate” analyses could not be correlated with chemical characteristics studied samples. Therefore, provide two sets working specific to these classes methodologies current data calibration.