Chemical Separation and Isotopic Variations of Cu and Zn From Five Geological Reference Materials

Abstract

This paper presents an adapted anion exchange column chemistry protocol which allowed separation of high‐purity fractions of Cu and Zn from geological materials. Isobaric and non‐spectral interferences were virtually eliminated for consequent multiple‐collector ICP‐MS analysis of the isotopic composition of these metals. The procedure achieved ∼ 100% recoveries, thus ensuring the absence of column‐induced isotopic fractionation. By employing these techniques, we report isotopic analyses for Cu and Zn from five geological reference materials: BCR‐027 blende ore (BCR), δ 65 Cu = 0.52 ± 0.15‰ (n = 10) and δ 66 Zn = 0.33 ± 0.07‰ (n = 8); BCR‐030 calcined calamine ore (BCR), δ 66 Zn = ‐0.06 ± 0.09‰ (n = 8); BCR‐1 basalt (USGS), δ 66 Zn = 0.29 ± 0.12‰ (n = 8); NOD‐P‐1 manganese nodule (USGS), δ 65 Cu = 0.46 ± 0.08‰ (n = 10) and δ 66 Zn = 0.78 ± 0.09‰ (n = 9); SU‐1 Cu‐Co ore (CCRMP), δ 65 Cu = ‐0.018 ± 0.08‰ (n = 10) and δ 66 Zn = 0.13 ± 0.17‰ (n = 6). All uncertainties are ± 2s; copper isotope ratios are reported relative to NIST SRM‐976, and zinc isotope ratios relative to the Lyon‐group Johnson Matthey metal (batch 3‐0749 L) solution, JMC Zn. These values agree well with the limited data previously published, and with results reported for similar natural sample types. Samples were measured using a GVi IsoProbe MC‐ICP‐MS, based at the Natural History Museum, London. Long‐term measurement reproducibility has been assessed by repeat analyses of both single element and complex matrix samples, and was commonly better than ± 0.07‰ for both δ 66 Zn and δ 65 Cu.