Scaling NIST SRM 3149 for Se isotope analysis and isotopic variations of natural samples

Literature values (δ82/76Se) were recalculated in the NIST 3149 scale. Troïlite from various iron meteorites yield zero per mil with a small variation of ± 0.39‰. Mafic terrestrial rocks also have a zero per mil composition on average, but with a larger variation of ± 0.72‰. Sediments (marine and continental) have a slightly positive average composition (0.39‰) with an even larger variation of ± 1.11‰. Sulfides from modern hydrothermal fields and various black shales yield rather negative average values of − 1.26‰ and − 0.57‰ respectively but with a relatively large range in composition (± 2.6‰ and ± 4.9% respectively). These large variations in δ82/76Se suggests that surface cycling may lead to significant isotopic fractionation, certainly due to Se phase transformations related to the different environmental conditions.