Hamersley province iron ore more than a billion years younger than thought

Ancient iron ore deposits in the Pilbara are more than a billion years younger than previously thought with researchers indicating it could inform mining exploration in the region. The Hamersley province, which sits 500km south of Karratha, is home to the Earth’s largest iron ore deposits which were originally thought to be formed 2.2 billion years ago. But researchers from Curtin University have discovered the deposits are actually between 1.4b and 1.1b years old by using a new geochronology technique to accurately measure the age of iron oxide minerals. Lead author Dr Liam Courtney-Davies said the findings showed iron deposits formed when ancient supercontinents were breaking apart and new ones were forming. He said the research would help miners decide where to explore for iron. “The energy from this epic geological activity likely triggered the production of billions of tonnes of iron-rich rock across the Pilbara,” he said. “The discovery of a link between these giant iron ore deposits and changes in supercontinent cycles enhances our understanding of ancient geological processes and improves our ability to predict where we should explore in the future.” Study co-author Associate Professor Martin Danisik said the research precisely dated minerals from banded iron formations, which are ancient underwater layers of iron-rich rock that can provide significant insights into the Earth’s deep geologic past. “Until now, the exact time line of these formations changing from 30 per cent iron as they originally were, to more than 60 per cent iron as they are today, was unclear, which has hindered our understanding of the processes that led to the formation of the world’s largest ore deposits,” he said. “By using an emerging technique to date iron oxide minerals through uranium and lead isotope analysis within the mineral grains, we directly dated all the major giant BIF-hosted iron ore deposits in the Hamersley province. “Our research indicates these deposits formed in conjunction with major tectonic events, highlighting the dynamic nature of our planet’s history and the complexity of iron ore mineralisation.” WA is the world’s leading producer of iron ore and is Australia’s largest export, earning $131b last financial year. The research was done in collaboration with researchers from the University of Western Australia, Rio Tinto and CSIRO Mineral Resources.