Oct 12, 2020

‘Elegant solution’ to target rare earth concentrations

‘Elegant solution’ to target  rare earth concentrations

University of Exeter researchers have revealed a new hypothesis to predict where rare earth elements neodymium and dysprosium could be found.

The elements are an essential part of digital and clean energy manufacturing, including magnets in large wind turbines and electric car motors.

Research led by Professor Frances Wall from the University of Exeter’s Camborne School of Mines showed that sodium and potassium – rather than chlorine or fluorine as previously thought – were the key ingredients for making these rare earth elements soluble.

The experiments could allow geologists to make better predictions about where the best concentrations of neodymium and dysprosium are likely to be found.

University of Exeter researchers, through the ‘SoS RARE’ project, have previously studied many natural examples of the roots of very unusual extinct carbonatite volcanoes, where the world’s best rare earth deposits occur, in order to identify potential deposits of the rare earth minerals.

To gain a greater insight into their results, they invited Michael Anenburg to join the team to carry out experiments at the Australian National University (ANU).

Co-authors Corinne Frigo and Michael Anenburg in front of a piston cylinder apparatus at the Research School of Earth Sciences, Australian National University.

He simulated the crystallisation of molten carbonate magma to find out which elements would be concentrated in the hot waters left over from the crystallisation process.

It showed that sodium and potassium make the rare earths soluble in solution. Without sodium and potassium, rare earth minerals precipitate in the carbonatite itself. 

With sodium, intermediate minerals like burbankite form and are then replaced. With potassium, dysprosium is more soluble than neodymium and carried out to the surrounding rocks.

Professor Frances Wall, leader of the SoS RARE project said: “This is an elegant solution that helps us understand better where ‘heavy’ rare earths like dysprosium and ‘light’ rare earths like neodymium’ may be concentrated in and around carbonatite intrusions. We were always looking for evidence of chloride-bearing solutions but failing to find it. These results give us new ideas.”

Dr Anenburg , a Postdoctoral Fellow at ANU said: “My tiny experimental capsules revealed minerals that nature typically hides from us. It was a surprise how well they explain what we see in natural rocks and ore deposits.”

‘Rare earth element mobility in and around carbonatites controlled by sodium, potassium, and silica’ was published in Science Advances on October 9, 2020.