Australian and Chinese university researchers have identified probable locations for critical metals needed to support a green economy by studying how critical metals accumulate at the margins of old cores of continents.
Led by China University of Geosciences Dr Chunfei Chen whose post-doctoral research is with the Earth Evolution research group at Macquarie University, said the probable locations and mechanisms of accumulations of critical metals are at the margins of old cores of continents.
“These cores are the thickest, bowl-shaped, parts of tectonic plates. Melts that form below their centres will flow upwards and outwards towards the edges, so that volcanic activity is common around their edges,” Chen said.
Previous high-pressure experiments in the Earth Evolution group have shown that initial melts at around 200 kilometres depth are rich in carbonate but contain much less silica than most rock melts.
The new experiments by Dr Chen and colleagues show that these melts will lose silica and become almost pure carbonate as they flow upwards and outwards beneath the continental cores.
Image: Nature Communications
Professor Stephen Foley from Macquarie’s School of Natural Sciences said the link to critical metals lies in this change in melt composition.
“The initial melts can carry lots of critical metals and sulfur, but our new results show that these are dropped by the melt as it loses silica. This causes concentrations of critical metals and sulfur in linear arrangements around the edges of thick continental cores,” Foley said.
The research also confirms that mantle samples brought to the surface in volcanoes in these areas contain more sulfur and copper than elsewhere on the continents.
The new work explains recent observations by researchers at the Canberra-based Australian National University and Geoscience Australia, which both found critical metals accumulated around the edges of continent cores, homing in on critical mineral hotspots.
The researchers’ findings have been published in the journal Nature Communications, in a paper called Sulfide-rich continental roots at cratonic margins formed by carbonated melts.
To transition to a green economy, more critical metals such as copper, rare earth elements and cobalt than are currently available, are required.
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