The stable tungsten isotope composition of modern igneous reservoirs

Tungsten is a highly incompatible and fluid mobile element in the Earth’s crust and mantle, but its geochemical cycle in magmatic systems still remains poorly understood. Tungsten stable isotopes represent a novel tool with the potential to better constrain this cycle, because of possible W isotope fractionation during changes in redox-state (valence states +4 and +6) and coordination (tetrahedral and octahedral). By employing a 180W-183W double spike our analytical protocol for stable W isotope measurements yields an external reproducibility of ±0.018‰ (2 s.d.) in δ186/184W and enables the resolution of small scale stable W isotope variations between different igneous reservoirs.