A new study shows that the world’s largest iron ore deposits were formed when the ancient supercontinent, Columbia, split up about 1.4 billion years ago.
These deposits are now found in the Hamersley Province in Western Australia. They rest on a very old piece of Earth’s crust called the Pilbara Craton.
The Pilbara Craton is one of only two crust pieces that date back to the Archaean Eon, which lasted from 3.8 billion to 2.5 billion years ago. Moreover, this area contains some of the oldest rocks on Earth. The other piece of ancient crust is the Kaapvaal Craton, located in southern Africa, according to Live Science.
Birth and breakup of several supercontinents
Rocks in the Pilbara Craton have experienced the formation and breakup of several supercontinents. This history means they contain important clues about the origins of the area’s rich mineral deposits, according to researchers.
The study highlights the breakup of the supercontinent Columbia, which existed between 1.7 billion and 1.45 billion years ago.
After Columbia broke apart, Australia began to come together between 1.4 billion and 1.1 billion years ago. This process likely explains how the large iron ore reserves in the Hamersley Province were formed. The team published their findings on July 23rd 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,” said Liam Courtney-Davies, the study’s lead author and a geochronologist at the University of Colorado, Boulder.
More than 55 billion tons of iron ore in Hamersley Province
The Hamersley Province contains over 55 billion tons of iron ore. Geologists previously believed these deposits formed around 2.2 billion years ago. However, the new study, using direct dating techniques, found that the deposits are much younger. They actually formed between 1.4 billion and 1.1 billion years ago.
To determine the age of the deposits, Courtney-Davies and his team studied minerals in eight large blocks of sedimentary rock known as banded iron formations. Moreover, these rocks have alternating layers of iron-rich minerals like magnetite and hematite, and iron-poor minerals like chert.
The researchers used a new method that involves analyzing uranium and lead isotopes within the iron oxides. This technique provided the first direct age measurements for the iron ore deposits in the Hamersley Province.
The study found that iron ore formed when the supercontinent Columbia, also known as Nuna, broke apart. This event led to the formation of an early Australian continent.
“Our research indicates these deposits formed in conjunction with major tectonic events,” said Martin Danisik, a co-author of the study and an associate professor of geology at Curtin University in Australia.
