A new study from Curtin University has found that water was transported much deeper into the early Earth than previously thought, shedding new light on how the continents originally formed.
The study, published in Earth and Planetary Science Letters, answers long-standing questions about Earth’s early water cycle.
Lead researcher Dr Michael Hartnady, from the Curtin School of Earth and Planetary Sciences, said how water is stored and transported through the Earth’s crust influences everything from where the volcanoes and mineral deposits to where earthquakes occur.
“While we understand the modern deep-water cycle, we know very little about how it worked when Earth was still a very young planet,” Dr Hartnady said.
“Multiple lines of geological evidence show that water was transported to great depths within the Earth as far back as 3.5 billion years ago, although exactly how it got there is not well understood.”
The researchers used sophisticated modeling to show that early high-magnesium volcanic rocks, which erupted on the ocean floor on early Earth, would have absorbed much more seawater than more modern lavas.
“This water, which is locked in particular crystals within the rock, would have been released when the rocks were buried and began to ‘sweat.’ In modern lavas, this sweating occurs at a temperature of about 500 degrees degrees Celsius,” Dr Hartnady said.
“Our findings indicate that much of the seawater initially bound to the ancient primitive lavas would have been released at much higher temperatures, in excess of 700 degrees Celsius.
“Importantly, this means that water was transported much deeper into the early Earth than previously thought. Its release would have caused the surrounding rocks to melt, eventually forming the continents.”
Dr Hartnady said this research helped explain the inner workings of the planet for more than 2.5 billion years.
“Interestingly, the oldest parts of the continents, the cratons, also contain some of the largest gold deposits on Earth, including the Golden Mile near Kalgoorlie,” Dr Hartnady said.
“These gold deposits required large volumes of water to form, and we still don’t have a good explanation for where it came from. Our new research may help solve these and other questions, perhaps even those related to the origins of life”.
This research was funded by the Australian Research Council, Geological Survey of Western Australia and Northern Star Resources Ltd.
The full paper, titled “Fluid Processes on the Early Earth and the Growth of the Continents” is available online here.