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oxygen isotopes, sulfur isotopes, sulfates, SIMS, GS-IRMS, EBSD
Abstract:
Secondary ion mass spectrometry was used to test the d18O and d34S nanogram-scale homogeneity of a suite of
candidate sulfate minerals, ultimately selecting three barite, two anhydrite, and two gypsum samples from the Royal
Ontario Museum that have repeatabilities for their SIMS measurements of better than 0.39‰ and 0.37‰ (1s) for
oxygen and sulfur isotope ratios, respectively. Metrological splits of each of the seven materials were sent to multiple gas
source isotope ratio mass spectrometry laboratories in order to establish their absolute 18O/16O and 34S/32S ratios. The
inter-laboratory results of GS-IRMS analyses yielded reasonably narrow ranges in d18OVSMOW, whereas larger variations
in d34SVCDT values were found between the results from the gas source laboratories. All samples have good reproducibility
within laboratories of GS-IRMS 103d18O values of between 0.24‰ and 0.44‰ (1s). The reproducibility within
laboratories of GS-IRMS 103d34S values range from 0.07‰ to 0.99‰ (1s). Here we also discuss some of the current
analytical limitations affecting these isotope-mineral systems. A total of 256 metrological splits have been prepared from
each of these seven materials; these aliquots will be made available to the global geochemical community.
