Research from Adelaide University has identified ancient tectonic processes as a key factor in locating rare earth elements (REEs), which are critical for modern technologies and the global clean energy transition.
Published in Science Advances, the study links the formation of REE deposits and carbonatites – igneous rocks known to host these resources – to ancient subduction zones, where tectonic plates collide and one is forced beneath another.
Rare earth elements are widely used in electric vehicles, wind turbines, smartphones, and defence systems, but economically viable deposits remain difficult to locate.
The research team, led by Carl Spandler from the School of Physics, Chemistry and Earth Sciences, reconstructed Earth’s geological history over the past two billion years using plate tectonic modelling.
The study found that mantle regions “fertilised” by subduction processes now underlie about 67 per cent of carbonatites and 72 per cent of REE deposits formed over the past 1.8 billion years. For older deposits, this figure rises to 92 per cent.
Professor Spandler said the findings point to a long-term geological process behind the formation of these resources.
“This research shows that the ingredients for these critical mineral deposits were put in place many million to even billions of years ago,” he said. “By identifying where these ancient processes occurred, we can significantly narrow down the search areas for future discoveries.”
The research challenges earlier theories that primarily linked such deposits to mantle plumes, instead proposing a two-stage process. According to the study, subduction first enriches the mantle, followed – sometimes much later – by events that trigger melting and magma formation.
“This time lag is one of the most surprising aspects of our findings,” Professor Spandler said. “It shows that the Earth’s mantle can store these enriched zones for incredibly long periods before the right conditions arise to form mineral deposits.”
Co-author Andrew Merdith said the findings could improve how exploration is conducted. “By focusing on these ancient tectonic zones, exploration companies and governments can take a more targeted and efficient approach to finding new deposits,” he said, noting growing global demand for rare earth elements.
The team also mapped these subduction-influenced regions, estimating they cover around 35 per cent of Earth’s continental crust. Areas with overlapping subduction events were found to host particularly high concentrations of REE deposits.
Beyond resource exploration, the study provides insights into Earth’s geological evolution and the long-term storage of carbon and water in the mantle, with implications for understanding past climate and volcanic activity.
The research was conducted in collaboration with the ARC Centre in Critical Resources for the Future.
