New research from the University of St Andrews will help rare earth explorers identify where rare earth metals are located.

The study was launched to determine why some volcanoes are excellent sources of rare earth metals, while others are not.

Scientists determined that fluids that leak from the magma body to then be embedded into surrounding rocks can bring substantial quantities of rare earths metals. The fluids scatter the metals, making it hard for miners to identify an economically viable deposit.

"This is the first time that the mass of material transported by this process was estimated," lead researcher Krzysztof Sokół said. "We also present a new way to visualise the distribution of metals in the surrounding rock."

The new study demonstrates that during volcanic eruptions, the melts at the shallow level of the Earth's crust "can form a separate hot fluid enriched in critical metals," which then leaks into surrounding rocks, Phys.org reported.

Researchers said the total amount of rare earth metals carried by this process is approximately 40 megatonnes, similar to amounts at the world's largest rare earth deposits.

The study has improved scientists' knowledge of how rare earths metals deposits are formed on volcanoes.

"Armed with this information, we can guide far better exploration for the next generation of green technologies," St Andrews' Adrian Finch and Will Hutchison said.