Primordial helium extracted from the Earth's core through magnesium oxide exsolution

Primordial helium in the deep mantle may be supplied continuously from Earth's core, according to first-principles calculations and modelling of helium partitioning into exsolved magnesium oxide at core-mantle boundary conditions Helium is considered a key tracer for processes in Earth's deep interior as the core is thought to be a reservoir for the primordial isotope He-3. High He-3/He-4 ratios in ocean island basalts fed by mantle plumes are indicative of relatively undegassed reservoirs preserved in the deep mantle. Notably, ocean island basalts with tungsten isotopic and He-3/He-4 anomalies point to possible material contributions from the core. However, it remains unclear how helium is transported from the core to the mantle. Here we use first-principles calculations to show that helium strongly favours entering magnesium oxide at core-mantle boundary conditions. This suggests that magnesium oxide exsolved from the core can deliver appreciable amounts of helium back into the mantle. We also modelled the expected helium flux due to magnesium oxide exsolution since core formation, showing that magnesium oxide exsolved from the core may have continuously supplied helium from the core into the mantle throughout much of Earth's history, imprinting its primordial helium signature into the mantle materials. Moreover, magnesium oxide exsolution may inherit other distinct geochemical signatures from the core, thereby offering a pathway for probing core processes.

Automated summary

Research suggests that primordial helium in the deep mantle could be continuously supplied from Earth's core through the exsolution of magnesium oxide. This finding has significant implications for understanding Earth's interior processes and the role of the core.