A volcano has erupted remnants of Earth's primordial magma ocean — SkimNews
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- Fani Maoré volcano, about 50 km east of Mayotte, was discovered after a May 2018 earthquake swarm; eruptions over the next three years drained so much magma that Mayotte itself sank roughly 20 centimeters.
- Catherine Chauvel at CNRS Paris and Claudine Israel at Cambridge used a newly developed ultra-precise technique to measure neodymium isotope ratios, finding Fani Maoré lava carries a higher neodymium-142 to neodymium-144 ratio than nearby Mayotte lava.
- That ratio points to a pocket of ancient mantle rich in bridgmanite, a mineral thought to be among the very first to crystallize from Earth's primordial magma ocean following the Mars-sized impact during the Hadean eon.
- Chauvel said the find provides proof that materials from 'the very beginning of Earth's history' still exist in sufficient quantities to be sampled in an active volcano — something prior analytical techniques couldn't confirm.
- The findings challenge the prevailing view that Earth's mantle became thoroughly mixed over billions of years, with Tim Johnson at Curtin University calling it 'an exciting advance' in reconstructing how the early mantle solidified.
- Bernard Bourdon at CNRS Lyon compared the discovery to 'discovering a sample of Earth's core that somehow made it all the way to the surface,' while Richard Carlson at Carnegie Science called the measurement precision itself 'a major achievement.'
Why it matters: Geologists had assumed Earth's mantle is essentially homogenized after 4 billion years of churning, erasing any record of the planet's earliest chemistry. This study's neodymium-142/144 fingerprint at Fani Maoré gives researchers the first direct sample of Hadean-era material, opening a window onto the magma ocean's solidification sequence — and contradicting the long-standing 'well-mixed mantle' assumption that has shaped models of early Earth.
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