Lava from Mayotte-area volcano shows slightly higher neodymium-142 ratio than older local flows

Lava from a newly formed underwater volcano east of Mayotte contains chemical evidence of mantle material that dates to the first 100 million years of Earth's history. @NewScientist reported that samples from Fani Maoré, discovered in 2018 after an earthquake swarm 50 km east of the island, show a slightly higher ratio of neodymium-142 to neodymium-144 than lava from the older Mayotte volcanic system.

Researchers recovered rock samples from both volcanoes and applied an ultra-precise measurement technique developed with Claudine Israel at the University of Cambridge.

Catherine Chauvel of the French National Centre for Scientific Research in Paris said the higher isotope ratio indicates a pocket of ancient mantle still rich in bridgmanite, a mineral among the first to crystallise from the global magma ocean that covered Earth after a Mars-sized impact.

Eruptions at Fani Maoré over three years drained enough magma to cause Mayotte to sink about 20 cm. The study, published in Nature with DOI 10.5 billion years ago in quantities large enough to be sampled.

"This is going to change a lot of things in earth science, because now we have proof that materials dating back 4.5 billion years still exist in sufficient quantities to be sampled in a volcano," Chauvel said. Israel noted that the measurements demonstrate how the mantle crystallised from the magma ocean and created chemical heterogeneity from the start.

Tim Johnson at Curtin University called the results an exciting advance.

Bernard Bourdon at CNRS in Lyon said the precision of the measurements represents a major achievement, while Richard Carlson at Carnegie Science described it as noteworthy for anyone experienced with such analyses.