New underwater volcano near Mayotte shows slightly higher neodymium-142 ratio than nearby older volcanoes

Lava from the underwater volcano Fani Maoré contains a slightly higher ratio of neodymium-142 to neodymium-144 than lava from the older volcanic system on nearby Mayotte. @NewScientist reported that the difference points to a pocket of mantle material that escaped mixing for more than 4 billion years and retains chemical signatures from Earth's primordial magma ocean.

An earthquake swarm off Mayotte in May 2018 led to the discovery of Fani Maoré, located about 50 km east of the island.

Eruptions over the next three years drained enough magma to cause Mayotte to sink roughly 20 cm. A 2019 submarine survey produced relief images of the new volcano. Catherine Chauvel at CNRS in Paris said the results show that materials dating back 4.5 billion years still exist in sufficient quantities to be sampled in a volcano.

Claudine Israel at the University of Cambridge collaborated on the study, which used a newly developed ultra-precise technique to measure the neodymium isotope ratios. The higher ratio in Fani Maoré lava is consistent with enrichment in bridgmanite, a mineral among the first to crystallize from the global magma ocean that formed after a Mars-sized impact during the Hadean eon.

The study was published in Nature.

Tim Johnson at Curtin University said the findings provide plausible evidence that Earth's mantle still preserves extremely ancient material. Bernard Bourdon at CNRS in Lyon compared the discovery to finding a sample of Earth's core that reached the surface.