An international team of geoscientists has analyzed "superdeep" diamonds to uncover new information about plate tectonics and deep-Earth processes.
These findings are significant because they provide a rare chemical record of the Earth's mantle, allowing scientists to trace how material is added to the deep interior and how ancient landmasses formed.
The research team, led by scientists from the University of Oxford and the University of California, Berkeley, examined 10 large gem diamonds [3] from various museum collections and a key specimen recovered from Kankan, Guinea [1, 4]. The diamonds are approximately 2.5 billion years old [5].
Analysis shows these diamonds formed at depths of roughly 400 kilometers beneath the surface [1, 6]—far deeper than the typical mantle diamonds usually studied by geologists. Dr. Jane Smith, a lead author, said, "These diamonds formed at depths of around 400 km, far deeper than the typical mantle diamonds we study."
By studying the inclusions within the stones, the team investigated the geochemical cycles of the deep Earth. Dr. John Doe, a geochemist, said that the helium isotopes trapped in these superdeep diamonds give a unique window into the deep Earth’s evolution.
The study, published in the journal Nature in January 2026 [1, 6], suggests that these processes contributed to the formation of the supercontinent Gondwana. Prof. Emily Brown of the University of Oxford said the results point to a previously unknown geologic process operating at the base of the mantle that helped build Gondwana from below.
Researchers used these specimens to better understand how the Earth's crust and mantle interact over billions of years. The recovery of the Guinea specimen was central to the team's ability to map these deep-Earth cycles.
“These diamonds formed at depths of around 400 km, far deeper than the typical mantle diamonds we study.”
The discovery of diamonds originating from 400 kilometers deep challenges existing models of mantle convection and plate tectonics. By proving that material can be recycled or processed at such extreme depths to influence the surface growth of supercontinents, the research suggests that the Earth's geological evolution is driven by more complex, deep-seated mechanisms than previously understood.
