A new study by University of Sydney researchers could help improve exploration success for copper and other critical minerals by revealing why some ancient continental edges became rich in mineral deposits while others with similar geology remained barren.
Published in Nature Communications, the research 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.
The study found that understanding the deep-time geological processes responsible for concentrating these resources could reduce uncertainty in mineral exploration and support long-term resource security.
Led by PhD student Hojat Shirmard and Professor Dietmar Müller from the University of Sydney’s School of Geosciences, the research developed a dynamic model reconstructing Earth’s evolution over the past 1.8 billion years to identify why mineralised ore bodies formed in some locations but not others.
While scientists have long recognised that many sediment-hosted mineral deposits occur along the edges of ancient continental cores known as cratons, the new study identified which sections of those margins are most prospective by linking mineral formation to tectonic plate movements and the circulation of Earth’s mantle.
The researchers found mineral-rich craton edges commonly formed between 800 km and 1800 km from ancient subduction zones, where one tectonic plate sinks beneath another. According to the study, this distance corresponds with areas where deep-Earth mantle flow concentrates stress and weakens the continental lithosphere, creating favourable conditions for mineralisation.
“Many of these deposits formed far from tectonic plate boundaries, but our results show they were still linked to subduction,” Shirmard said.
“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 move through the Earth’s crust, forming ore deposits in faults, rifts and other geological structures.
The research combined a global tectonic plate motion model spanning 1.8 billion years with seismic tomography, geodynamic modelling and a database of more than 2000 mineral deposits.
The analysis showed mineral deposits cluster significantly closer to ancient subduction zones than would be expected by chance. The median distance between deposits and ancient trenches was about 1200 km, while more than 90 per cent of the total metal content analysed occurred within 2200 km of ancient subduction zones.
Numerical modelling also showed that deep mantle convection generated by subduction can weaken craton edges by reactivating ancient geological structures and promoting rifting, helping prepare the crust for the formation of major sediment-hosted copper, lead and zinc deposits.
Professor Müller said the findings demonstrated that mineral systems are controlled by processes extending far beyond local geology.
“Our work shows that mineral deposits are not just controlled by local geology,” 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.”
Professor Müller said tools developed by the EarthByte Group and its partners allow researchers to reconstruct Earth’s deep-time evolution and convert that knowledge into practical insights for Australia’s minerals sector.
Subscribe to Australian Mining and receive the latest news on product announcements, industry developments, commodities and more.
