Study shows how to track valuable ‘green’ metals from depths of Earth

SYDNEY — Australian researchers have in a new study discussed how low temperature and carbon-rich melts can help bring concentrations of valuable metals, used in renewable energy technologies, from deep within the Earth’s interior mantle.

The team from Macquarie University carried out high-pressure and high-temperature experiments which created small amounts of molten carbonate material. The temperatures were akin to those around 90 kilometres deep in the mantle, below the Earth’s crust.

A majority of the rock in the Earth’s crust is silicate in composition, but a tiny proportion of carbon and water gets melted with lower temperatures.

The findings, published in the journal Science Advances, showed that the “carbonate melts can dissolve and carry a range of critical metals and compounds from surrounding rocks in the mantle.”

These include nickel, copper, cobalt, gold and silver, as well as oxidised sulphur.

“We knew that carbonate melts carried rare earth elements, but this research goes further,” said Dr. Isra Ezad, a postdoctoral research student at Macquarie’s School of Natural Sciences.

“We show this molten rock containing carbon takes up sulphur in its oxidised form, while also dissolving precious and base metals — ‘green’ metals of the future — extracted from the mantle,” Ezad added.

This is more important due to the soaring demand for these essential metals and hard-to-find reliable sources, Dr. Ezad said, stressing the importance of tracking carbonate melts.