Ba isotope geochemistry of the mantle

Barium is a large ion lithophile alkaline-earth element and it is also fluid-mobile. Since Ba is highly incompatible during mantle melting, Ba content in the crust is much higher than that in mantle. Ba isotopes can be significantly fractionated in low-temperature conditions or during fluid processes, but Ba isotope fractionation in mafic-intermediate magmatism is negligible. Therefore, Ba isotopes have been recently used as a novel tool to study recycling of subducted materials, especially in tracing the effect of fluid and sediment on the composition of the mantle. It is a prerequisite to estimate the average Ba isotope compositions before applying Ba isotopes to high temperature geochemistry studies. Ba isotope data for the mantle are still rare and controversial. This study summarizes Ba isotope analytical method, fractionation mechanism, and composition of important reservoirs. We focus on Ba isotope variation on basaltic rocks, behavior of Ba isotopes during magmatism and metamorphism, and potential applications. We believe that the future of Ba isotopes will be quite promising.