Iron Isotope Ratios of IAEA B5 Basalt and Whole-Rock Reference Materials (JB-2, BHVO-2, AGV-1, BE-N and RGM-1) Determined by Multi-Collector Inductively Coupled Plasma-Mass Spectrometry

Iron isotopes are increasingly applied in Earth science fields, including cosmochemistry, geochemistry and environmental sciences. Refining non-traditional stable isotope systematics requires well-characterised isotopic reference materials to ensure accuracy and precision. Consequently, the direct comparison of data obtained from different laboratories is a key prerequisite for establishing reliable isotopic systematics. Here, we describe a new Fe isotope measurement method using multi-collector-ICP-MS. The Fe isotope ratios of widely used geological reference materials (JB-2, BHVO-2, BE-N, AGV-1 and RGM-1) were measured and new Fe isotope values for IAEA-B5 (basalt from Mount Etna, Italy) are recommended. Anion exchange chromatography was used to separate Fe from the rest of the matrix. Mass bias was corrected using a standard-sample-standard bracketing method combined with Ni-doping. Iron isotope ratios of JB-2, BHVO-2, BE-N, AGV-1 and RGM-1 show strong agreement with published values and fall within reported analytical uncertainties. Based on these results, we validate and propose delta 56Fe = 0.103 +/- 0.064 (2s) and delta 57Fe = 0.141 +/- 0.068 (2s) as recommended values for IAEA-B5. We further advocate the IAEA-B5 as a robust and complementary reference material for analytical validation and quality control in Fe isotope studies, providing both a supplement to and an alternative for established iron isotope reference materials.