New research from Macquarie University has identified the likely location of major metals that are critical to the development of a green economy. The transition to a green economy requires far more critical metals such as copper, rare earth elements and cobalt than current reserves can supply. To eliminate this shortage, it is important to discover new metal resources formed by various geological processes in previously unexplored regions.
A new study published on January 8, 2025 in Nature magazine, led by Dr Chunfei Chen during his postdoctoral work with the Earth Evolution Research Group at Macquarie University, sheds light on where and how critical metals are likely to accumulate. The study identifies the margins of ancient continental cores as promising sites for these metal deposits and explains the geological mechanisms of their formation.
“These cores are the thickest parts of the bowl-shaped tectonic plates. The melts that form under their centers will flow upwards and outwards towards the edges, so volcanic activity is common around their edges,” says Chen.
The role of carbonate-rich melts in the concentration of metals
Previous high-pressure experiments by the Earth Evolution team have shown that the initial melts at a depth of about 200 kilometers are rich in carbonates but contain much less silica than most rock melts. The new experiments by Dr. Chen and his colleagues show that these melts will lose silica and become almost pure carbonates as they flow up and out beneath the continental cores. Distinguished Professor Stephen Foley from Macquarie's School of Life Sciences explains that the link with critical metals lies in this change in melt composition.
"Initial melts can contain many critical metals and sulfur, but our new results show that these are lost to the melt as it loses silica. This causes critical metals and sulfur to concentrate in linear arrangements around the edges of thick continental cores," says Professor Foley.
The study also confirms that mantle samples brought to the surface by volcanoes in these areas do indeed contain more sulfur and copper than elsewhere on the continents. This new work explains recent observations by researchers at the Australian National University and Geoscience Australia, which found that critical metals accumulate around the edges of continental cores, and draws attention to these areas for future exploration.