“While we understand the modern deep-water cycle, we know very little about how it worked when Earth was still a very young planet,” lead researcher Michael Hartnady said in a media release. “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.”
Hartnady and his team 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 centigrade,” said the scientist.
But recent results indicate that much of the seawater originally bound to the ancient primitive lavas would have been released at much higher temperatures, in excess of 700 degrees Celsius.
According to Hartnady, this means that water was transported much deeper into the early earth than previously thought, and that its release would have caused the surrounding rocks to melt, eventually forming continents.
“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,” the researcher said. “These gold deposits required large volumes of water to form, and we still don’t have a good explanation for where that water came from. Our new research may help solve these and other questions, perhaps even related with the origins of life”.