Researchers at Macquarie University have revealed how critical minerals can be transported from the Earth’s interior mantle.
The critical minerals used in renewable energy technologies can be transported from within the Earth’s interior mantle by low-temperature carbonate melts.
Published in Science Advances, the findings have the potential to contribute to global mineral exploration efforts.
Carbon melts carry a range of critical minerals
Led by Dr Isra Ezad, a postdoctoral research fellow from Macquarie University’s School of Natural Sciences, the team carried out high-pressure and high-temperature experiments to create small amounts of molten carbonate material.
This was done in conditions similar to those around 90 kilometres depth in the mantle, below the Earth’s crust.
The study showed that carbonate melts can dissolve and carry a range of critical minerals and compounds from surrounding rocks in the mantle. This will inform future metal prospecting.
“We knew that carbonate melts carried rare earth elements, but this research goes further,” said Dr Ezad.
“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.”
Carbonate melts enriched in sulphur may be more widespread than thought previously
Most of the rock that lies deep in the Earth’s crust and below in the mantle is silicate in composition.
However, a fraction of a percentage of these deep rocks contains carbon and water, causing them to melt at lower temperatures than other portions of the mantle.
Carbonate melts transport base metals and precious metals, distilling these metals into potential deposits.
“Our findings suggest carbonate melts enriched in sulphur may be more widespread than previously thought, and can play an important role in concentrating metal deposits,” said Dr Ezad.
Two natural mantle compositions
The team used two natural mantle compositions, a mica pyroxenite from western Uganda and fertile spinel Iherzolite from Cameroon.
The team found that thicker continental crust regions form in older inland regions of continents, where they act as a sponge to soak up carbon and water.
“Carbon-sulphur melts appear to dissolve and concentrate these metals within discrete mantle regions, moving them into shallower crustal depths, where dynamic chemical processes can lead to ore deposit formation,” Dr Ezad said.
A new critical mineral exploration space
The study shows that tracking carbonate melts could give us a better understanding of large-scale metal redistribution and ore formation processes.
“As the world transitions away from fossil fuels to battery, wind and solar technology, demand for these essential metals is skyrocketing, and it’s becoming harder to find reliable sources,” said Dr Ezad.
“This new data provides us with a mineral exploration space previously not considered for base and precious metals – deposits from carbonate melts,” she concluded.
