A study led by geoscientists at the University of Sydney has revealed why some ancient continental edges became fertile sites for major mineral deposits, while others with apparently similar geology did not.
The research, published in Nature Communications , provides a new framework for understanding the distribution of sediment-hosted copper, zinc and lead deposits, which are important sources of metals used in infrastructure, manufacturing and clean-energy technologies.
Understanding the deep-time processes that concentrate these resources can help reduce uncertainty in exploration and support long-term resource security.
Led by first author and PhD student Hojat Shirmard and Professor Dietmar Müller from the School of Geosciences , the study developed a dynamic model of the Earth going back 1.8 billion years to identify how mineralised ores formed in specific places and not in other similar areas.
Scientists have long known that many of these mineral deposits occur along the edges of the ancient stable cores of continents, known as cratons. The new study goes further, by showing which parts of those edges are most likely to contain such deposits by linking mineral formation to the long-term movement of tectonic plates and the slow circulation of Earth's mantle, the nearly 3000-kilometre-thick layer of heated rock under the Earth's crust.
The team found that mineral-rich craton edges commonly formed between 800 and 1800 kilometres away from ancient regions where one tectonic plate sinks beneath another, known as subduction zones.
This distance matches zones where deep-Earth flows can focus stress and weakening in the continental lithosphere – the crust and the upper mantle – helping to create the conditions needed for mineralisation.
"Many of these deposits formed far from tectonic plate boundaries, but our results show they were still linked to subduction," said PhD student and lead author Hojat Shirmard from the EarthByte Group in the School of Geosciences at the University of Sydney.
"Deep mantle flow can transmit stress thousands of kilometres into a continent, helping to weaken craton edges and create the conditions needed for mineralisation."
Mineralisation occurs when magma and other heated fluids are pushed through the Earth's crust, causing solid minerals to form ores in faults, rifts, or other spaces due to the dynamic changes of temperature, pressure or chemistry. The ores are highly sought after in mineral exploration.
Co-author Professor Dietmar Müller , from the EarthByte Group at the University of Sydney, said the study provides a new way to understand mineral systems through deep time.
"Our work shows that mineral deposits are not just controlled by local geology," Professor Müller said. "They are also part of a much larger tectonic system linking subduction, mantle flow, continental deformation and the long-term evolution of Earth's resources."
"This is exactly the kind of discovery that national research infrastructure makes possible," Professor Müller said.
"Tools developed by the EarthBytes Group and partners allow researchers to reconstruct Earth's deep-time evolution and turn that knowledge into practical insight for Australia's minerals sector."
Why some continent edges become mineral-rich
Cratons are the ancient, stable cores of continents. Their margins are long-lived zones of weakness, often marked by faults and rifts, that can act as pathways for mineralising fluids.
For decades, sediment-hosted mineral deposits have been explained mainly in terms of local basin processes: metal sources, circulating fluids and chemical traps. But these explanations do not account for why some craton margins became exceptionally mineral-rich while others with similar geological settings remained comparatively barren.
The new study shows that the answer may lie deeper in Earth's interior.
Using a global tectonic plate motion model spanning the past 1.8 billion years, the researchers reconstructed the changing positions of craton edges, mineral deposits and subduction zones through time. They combined this with imaging techniques known as seismic tomography, along with geodynamic modelling and a global database of more than 2000 mineral deposits.
The analysis showed that mineral deposits cluster much closer to ancient subduction zones than random locations along craton edges. The median distance for deposits was about 1200 kilometres from a trench, and more than 90 percent of the total metal content analysed lies within 2200 kilometres of ancient subduction zones.
A deep-Earth engine for mineral systems
Numerical models helped explain why this distance matters. The simulations showed that subduction can generate deep convection currents in the lower mantle, known as broad mantle return-flow cells, extending thousands of kilometres from the trench.
These flows can focus stress and strain near craton edges, weakening the lithosphere, reactivating ancient structures and promoting rifting and permeability. Over geological time, these processes can help prepare the crust and mantle for the formation of major sediment-hosted copper, lead and zinc deposits.
The models found that strain was strongest when craton edges were around 1300 kilometres from a subduction trench, closely matching the median distance of about 1200 kilometres observed for the mineral deposits.
The study used plate reconstruction workflows built around GPlates , pyGPlates and GPlately to reconstruct craton boundaries, mineral deposits and subduction zones through deep time. GPlates and pyGPlates development is supported through the AuScope National Collaborative Research Infrastructure System program.
DOWNLOAD a copy of the research and images at this link .
VIDEO of 1.8 billion years of plate tectonics reconstruction available here .
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