A submarine volcano in the Indian Ocean has brought to the surface material from Earth’s primordial magma ocean, molten rock that crystallized more than 4.46 billion years ago, within the first 100 million years of the planet’s history. The discovery, published July 1 in Nature, is the first direct evidence that remnants of the magma ocean have survived in the mantle, untouched by more than four billion years of convection.
The volcano is Fani Maoré, located roughly 50 kilometers east of Mayotte in the Comoros Archipelago. It began erupting in May 2018 and continued for approximately three years, producing a volume of lava so large that the island of Mayotte sank by roughly 20 centimeters.
The key to the discovery lies in neodymium isotopes. A team led by Claudine Israel of the University of Cambridge and the Institut de Physique du Globe de Paris (IPGP) and Catherine Chauvel of CNRS and IPGP measured the ratio of neodymium-142 to neodymium-144 in 13 lava samples from Fani Maoré with unprecedented precision, achieving a reproducibility of 3.1 parts per million over two years.
Neodymium-142 is produced by the decay of samarium-146, which has a half-life of just 103 million years. That means the isotope system stopped generating new neodymium-142 roughly 500 million years after the solar system formed. Any positive anomaly in neodymium-142 today must therefore have been locked into a reservoir within the first 100 million years of Earth’s history and preserved ever since.
The Fani Maoré lavas showed a mean neodymium-142 excess of +3.2 parts per million, with a statistical significance of P = 9 x 10^{-6}. “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, from the very beginning of Earth’s history, still exist in sufficient quantities to be sampled in a volcano,” Chauvel said.
Two models, one winner
The team tested two explanations for the anomaly. The first, that the signal came from ancient crust extracted in the shallow mantle, would require 28 to 90 percent of the plume source to be Hadean material, an implausibly large volume that could not have survived mantle mixing over 4.5 billion years.
The second, and now favored, model traces the anomaly to the crystallization of the magma ocean itself. When the young Earth was struck by a Mars-sized object (the impact that formed the Moon), the entire planet melted into a global ocean of magma extending to the core-mantle boundary. As this ocean cooled, a mineral called bridgmanite (MgSiO3 in its perovskite structure) crystallized first, sinking into the deep mantle and carrying with it a distinctive chemical signature.
New high-pressure experiments conducted in laser-heated diamond anvil cells at 53 to 97 gigapascals and 3,200 to 3,700 Kelvin, conditions matching the deep magma ocean, showed that bridgmanite strongly favors samarium over neodymium. The result: early bridgmanite crystals had samarium-to-neodymium ratios up to 0.38, nearly double that of the bulk silicate Earth. Over time, this excess of samarium decayed into neodymium-142, producing the anomaly seen today.
The mixing model that best fits the data requires just 9 to 11 percent Hadean bridgmanite in the mantle source of Fani Maoré, along with roughly 0.4 percent recycled sedimentary material. This small but detectable proportion is consistent with geodynamic models showing that early-formed solids can survive billions of years of mantle convection.
“It’s a bit like discovering a sample of Earth’s core that somehow made it all the way to the surface,” said Bernard Bourdon of CNRS, who was not involved in the study.
Richard Carlson of the Carnegie Institution for Science called the isotopic measurements “a major achievement.”
What it means
The discovery validates a long-held theoretical prediction: that the magma ocean’s crystallization products did not fully mix back into the mantle, but were preserved as isolated chemical domains. It also demonstrates that Earth’s lower mantle, the largest layer of the planet, still contains relics of its earliest history, accessible at the surface through the right volcanic system.
The moon-forming impact that created the magma ocean happened around 4.5 billion years ago, roughly 50 to 70 million years after Earth’s initial accretion. The Hadean Eon, named for the hellish conditions that followed, lasted until the oldest known intact rocks formed roughly 4.03 billion years ago. The rocks from Fani Maoré predate even those ancient zircons found at Jack Hills, Australia.
“There are enormous work to get the technique working,” Bourdon said of the team’s analytical achievement.
For geochemists, the result opens a new window into the earliest chapter of Earth’s history, a chapter written in magma and preserved for billions of years, waiting for the right volcano to bring it back up.
Sources
- Israel C, Chauvel C, Inglis E, et al. “Hadean bridgmanite in the source of a present-day ocean island.” Nature (2026). DOI: 10.1038/s41586-026-10719-w
- “A volcano has erupted remnants of Earth’s primordial magma ocean.” New Scientist, July 3, 2026. https://www.newscientist.com/article/2532929-a-volcano-has-erupted-remnants-of-earths-primordial-magma-ocean/