Lasers light the way to discovery of ancient crust beneath Western Australia

By firing lasers finer than a human hair at tiny grains of a mineral extracted from beach sand, Curtin researchers have found evidence of a nearly four-billion-year-old piece of Earth’s crust that lies beneath southwest WA.

In a new finding that helps explain the planet evolution from uninhabitable to life-sustaining, principal investigator and Ph.D. student Maximilian Droellner, of the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences, said the lasers were used to cut parts of individual grains of the mineral zircon and revealed where the grains had originally eroded, as well as the geological history of the region.

“Evidence suggests that an up to four billion-year-old piece of crust the size of Ireland has influenced the geological evolution of WA over the past billions of years and is a key ingredient of rocks formed in WA during that time,” Droellner said.

“This piece of crust has survived multiple mountain-building events between Australia, India and Antarctica and appears to still exist tens of kilometers below the southwest corner of WA.

“When comparing our findings with existing data, it appears that many regions around the world have experienced similar timing of early crust formation and retention.

“This suggests a significant change in Earth’s evolution about four billion years ago, when meteorite bombardment waned, the crust stabilized and life on Earth began to settle.”

Research Supervisor Dr. Milo Barham, also of the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences, said no large-scale study of this region had yet been done and the results, when compared with existing data, provide exciting new insights.

“The edge of the old piece of crust seems to define an important crustal boundary that controls where economically important minerals are found,” said Dr. Barham.

“Recognizing these ancient crustal remnants is important for the future of optimized sustainable resource exploration.

“Studying early Earth is challenging given the sheer amount of time that has passed, but it is vital to understanding the meaning of life on Earth and our quest to find it on other planets.”

The full research paper, “A persistent Hadean-Eoarchean protocrust in the western Yilgarn Craton, Western Australia” was published in the journal new earth†