A team of researchers has created aglobal map that may change how scientists search for rare earth deposits. Their work links unusual volcanic rocks to the oldest and thickest parts of Earth’s continents and points to a deeper geological pattern behind where these valuable resources are found.
Rare earth elements are used in products people rely on every day, including smartphones, electric vehicles, and wind turbines. As countries look to strengthen supply chains and reduce dependence on imports, understanding how these deposits form has become a growing area of research.
For a long time, geologists have known that rare earth deposits tend to cluster in certain places, but the reason has remained unclear. Most studies looked at individual regions or specific mines, leaving open the question of whether a broader global rule existed.
According to research published in Nature Geoscience, scientists led by the University of Cambridge decided to step back and examine the problem on a planetary scale. Their method combined chemical data from thousands of rock samples with seismic images that make it possible to observe what is happening deep beneath the Earth’s surface.
Looking For Clues In Strange Volcanic Rocks
The starting point was a group of unusual CO2-rich igneous rocks, which are known to be linked to conditions that can favor rare earth deposits. Lead author Dr. Emilie Bowmangathered chemical data from around 9,000 igneous rock samples collected across the world. These rocks all shared one characteristic: they contained high levels of dissolved carbon dioxide.
According to Bowman, the goal was not just to document where these rocks appear but to begin understanding whether their distribution could help predict where rare earth deposits may occur.
“Our research is beginning to provide a kind of predictive power for where we can expect these rocks and, by extension, their associated rare earth element deposits, to form,” she said.
For Professor Sally Gibson, who co-authored the study, these rocks have had an unusual history in geology. They were collected and catalogued for years but often treated as oddities rather than something with practical value. Some were first described between the 1800s and early 1900s and ended up with names tied to the places they were discovered or to their unusual mineral content. Gibson noted that:
“The terminology is so sprawling that you could almost make a new language from these rock names,” she added. “This, and their scientific complexity, has added confusion, and people have tended to steer away from them.”
Earthquake Waves Exposed A Hidden Pattern
As mentioned in the study, to understand what was happening below the surface, the team added another layer of information: seismic imaging. Using waves generated by earthquakes, researchers mapped differences in the thickness and structure of the lithosphere, the rigid outer shell of the planet.
Professor Sergei Lebedev explained that seismic data can create a kind of internal image of Earth, similar to the way sonar reveals shapes underwater. When the researchers compared the seismic maps with the rock database, a pattern appeared.
Rocks with the chemistry associated with rare earth enrichment were mostly located near the steep edges of Earth’s thickest and oldest continental lithosphere.
“We needed to put together these two pieces of the puzzle, the rock chemistry and seismic data, in order to make the connection,”as noted by Gibson. “Rocks with the right chemistry for enrichment occur only in very specific places, mainly along the steep edges of Earth’s thickest and oldest lithosphere.”
The Underground Origins Of Rare Earth Deposits
The researchers also proposed an explanation for why these areas stand out. As explained by the study, thick lithosphere creates conditions where mantle rocks remain under high pressure and relatively cool temperatures. That limits melting and produces only small amounts of magma deep underground.
Those magma pockets can become trapped beneath the lithosphere and slowly cool into CO2-rich igneous rocks. Later geological activity can partially melt these rocks again, gradually concentrating rare earth elements over time.
This first stage of the research focused on rocks formed within the last 200 million years. Gibson explained that older rocks have often been altered by mountain building and continental rifting, which makes them harder to study. The team’s next step is to apply the same approach to older geological records that include many of today’s known rare earth deposits.
“Now we have established this systematic behavior exists, we can go back further in time. It’s going to be more challenging, but I’m hopeful that this will be a key step in predicting mineral occurrences,” he concluded.
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