Ancient rocks reveal how water helped shape the world

New Curtin-led research has revealed that water played a far bigger role than previously thought in shaping Earth’s first continents, transforming the planet’s early crust and helping to build the landmasses we see today.

Published in Nature’s Communications Earth and Environment Journal, the research team studied 1.6-billion-year-old rocks from the Georgetown Inlier in northeast Queensland – home to some of the best-preserved pieces of continental crust on Earth.

Lead researcher Dr Silvia Volante, who completed the research at Curtin’s School of Earth and Planetary Sciences but is now based at ETH Zurich in Switzerland, said the findings could redefine our understanding of water’s role in Earth’s early evolution and its importance in shaping the continents we see today.

“In the early days of our planet, volcanic rocks erupted on the ocean floor and were then altered by hot water as they cooled down and solidified. Over time, these water-rich rocks were buried deep within the Earth’s crust, where the introduction of additional water caused them to partially melt at temperatures ranging from 700 to 750°C,” Dr Volante said.

“By analysing the oxygen levels within the rocks, the research team found a clear difference between the original volcanic rocks and the granitic rocks they turned into – suggesting an additional source of water from deep within the Earth’s mantle.

“The two sources of water which formed the continental crust rocks – one from the volcanic rocks themselves, and more surprisingly also from deep within the Earth – fuelled a chain reaction of melting which lasted millions of years and helped form the building blocks of the continents we live on today.”

Co-author ARC Laureate Fellow John Curtin Distinguished Emeritus Professor Zheng Xiang Li, also from Curtin’s School of Earth and Planetary Sciences, said the team was fortunate to be able to study Australia’s ancient rocks, which offer a rare and well-preserved record of how the Earth formed.

“We had an incredible opportunity to work in unique locations such as the Georgetown Inlier, which is one of the only places in the world where we can see all stages of continental crust formation locked in billion-year-old rock,” Professor Li said.

“Our next step is to investigate whether similar water-based melting processes occurred in even older crust fragments. Finding more well-preserved examples will help show just how crucial water movement in the Earth’s mantle was in shaping our planet’s early landscape.”

This research was funded by an Australian Research Council (ARC) Project.

The paper was co-authored by Dr Amaury Pourteau, Professor William Collins, Dr Luc Doucet, and Dr Hugo Olierook from Curtin’s School of Earth and Planetary Sciences, Dr Laure Martin from The University of Western Australia, and Associate Professor Matthijs Smit from the University of British Columbia.

The full paper titled, “Oxygen isotope shifts reveal fluid-fluxed melting in continental anatexis,” can be found online here.