We found the first natural evidence of kinetic Eu anomalies caused by melt-induced diffusion in mantle peridotite clinopyroxene. Such anomalies are classically regarded as a “ghost plagioclase” signature in oceanic basalts and widely used as a proxy for the presence of recycled oceanic crust in their mantle source. They can in fact be explained kinetically without requiring plagioclase. Experimentally constrained numerical models confirm the origin of the observed anomalies (Fig. 1) and show that diffusive fractionation is promoted by the pressure, temperature and redox conditions in the deep basalt sources. This is an impactful and timely contribution to the current efforts in unravelling the fate of recycled oceanic crust from the complex magmatic processes at play in the Earth’s interior.

Fig. 1. Europium anomalies and progressive LREE enrichment in measured and modelled clinopyroxene crystals.

The paper just came out in Nature Communications (open access): https://www.nature.com/articles/s41467-023-36753-0