A new study has identified ancient tectonic processes as a critical factor in locating rare earth element (REE) deposits, potentially reshaping mineral exploration strategies.
Researchers from University of Adelaide reconstructed Earth’s geological history over the past two billion years, linking the formation of REE deposits and carbonatites to ancient subduction zones, regions where tectonic plates collide, and one is forced beneath another.
The study found that mantle regions enriched through subduction processes now underlie around 67 per cent of carbonatites and 72 per cent of REE deposits formed over the past 1.8 billion years. For older deposits, the figure rises to 92 per cent.
Lead researcher professor Carl Spandler said the findings demonstrate the long-term geological origins of critical mineral systems.
“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.”
Rare earth elements are essential to technologies including electric vehicles, wind turbines and electronics, but economically viable deposits remain difficult to locate.
The research challenges previous exploration models that emphasised mantle plumes as the primary driver of REE formation. Instead, it proposes a two-stage process: initial mantle “fertilisation” during subduction, followed, sometimes billions of years later, by events that trigger melting and mineralisation.
“This time lag is one of the most surprising aspects of our findings,” 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.”
The team also mapped these enriched mantle regions globally, estimating they underlie about 35 per cent of the Earth’s continental crust. Areas where multiple subduction events overlap were found to host higher concentrations of REE deposits.
Co-author Andrew Merdith said the findings could improve targeting efficiency for exploration companies and governments.
“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.
“This is especially important as demand for rare earth elements continues to grow.”
The research was conducted in collaboration with the ARC Centre in Critical Resources for the Future.
