Beyond δ-values: Examples from triple magnesium- and triple silicon isotopes

Triple metal(oid) isotope systems can provide valuable insights into underlying fractionation mechanisms. However, the limited isotopic variability and the precision constraints of MC-ICP-MS analyses often hinder the resolution of differences in three-isotope space. As a result, correlated isotope ratios are typically used only as quality indicators for δ-value measurements.

In this study, I introduce a straightforward method to reduce uncertainty in triple isotope slope measurements using MC-ICP-MS. This approach is applied to Mg isotopes in carbonates, demonstrating improved precision. Additionally, two case studies of Si isotopes show that differences between equilibrium and kinetic fractionation slopes -on the order of ~10 ppm per ‰- can be resolved by enhancing the spatial resolution or simply by high-precision solution analyses for fractionations of approximately 3 ‰.

These advances in resolving triple isotope variations open new avenues for the application of metal(oid) isotopes as proxies in paleoenvironmental reconstructions.