Indian Ocean Volcano Lava Shows Traces of 4.5-Billion-Year-Old Mantle Material

Lava from an underwater volcano off Madagascar contains chemical traces of material from a global magma ocean that covered Earth more than 4.5 billion years ago. The findings come from rock samples recovered from Fani Maoré, located about 50 kilometres east of Mayotte. An earthquake swarm off Mayotte in May 2018 led to the volcano's discovery.

Eruptions over the next three years caused the island to sink roughly 20 centimetres. Researchers collected volcanic rock from Fani Maoré and nearby Mayotte for comparison. Catherine Chauvel at the French National Centre for Scientific Research and colleagues measured tiny differences in neodymium isotopes using an ultra-precise technique developed with Claudine Israel at the University of Cambridge.

The Fani Maoré lava showed a slightly higher ratio of neodymium-142 to neodymium-144 than lava from Mayotte. That ratio points to a pocket of ancient mantle still rich in bridgmanite, one of the first minerals to crystallise as the magma ocean cooled.

“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.

The study, published in Nature, indicates Earth's mantle was never mixed as thoroughly as many models assumed. Submarine surveys conducted off Mayotte in 2019 mapped the volcano's relief and supported the sampling effort. The impact of a Mars-sized body during the Hadean eon is thought to have created the magma ocean.

The molten rock crystallised over several million years, forming the planet's earliest crust.