World's largest iron ore deposits formed over 1 billion years ago in supercontinent breakup

The world's largest iron ore deposits formed when the ancient supercontinent Columbia broke up around 1.4 billion years ago, a new study suggests.

The deposits, located in what is now Hamersley Province in Western Australia, sit on a chunk of Earth's crust known as the Pilbara Craton. The Pilbara Craton is one of only two pieces of crust known to date back to the Archaean Eon (3.8 billion to 2.5 billion years ago) and hosts some of the oldest rocks on our planet. (The other Archaean crust is the Kaapvaal Craton in southern Africa.)

Rocks in the Pilbara Craton have witnessed the birth and breakup of several supercontinents, meaning they hold clues about the origins of the region's rich mineral deposits, researchers said in the new study. In particular, the breakup of supercontinent Columbia, which existed between 1.7 billion and 1.45 billion years ago, and the subsequent amalgamation of Australia between 1.4 billion and 1.1 billion years ago, could explain how huge iron ore reserves formed in the Hamersley Province.

The team revealed its findings in a study published July 23 in the journal PNAS.

"The energy from this epic geological activity likely triggered the production of billions of tons of iron-rich rock across the Pilbara," study lead author Liam Courtney-Davies, a geochronologist and postdoctoral associate at the University of Colorado, Boulder, said in a statement.

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The Hamersley Province holds more than 55 billion tons (50 metric gigatons) of iron ore, which geologists previously thought formed around 2.2 billion years ago. But based on direct dating techniques, the new study found the deposits are actually much younger than that, forming between 1.4 billion and 1.1 billion years ago.