Curtin University researchers have used lasers to find evidence of an almost four-billion-year-old piece of the Earth’s crust lying beneath WA’s South West.
The research, the results of which were announced this week, involved lasers finer than a human hair being employed to vaporise portions of individual grains of zircon extracted from beach sand.
The process revealed where the grains were originally eroded from and also painted a fuller picture of the geological history of the region.
“There is evidence that an up to four billion-year-old piece of crust about the size of Ireland has been influencing the geological evolution of WA for the past few billions of years and is a key ingredient of rocks formed in WA across this time,” lead researcher and Curtin University PhD student Maximilian Droellner said.
“This piece of crust has survived multiple mountain-building events between Australia, India and Antarctica and appears to still exist at tens of kilometres of depth under the South-West corner of WA.
“When comparing our findings to existing data, it appears many regions around the world experienced a similar timing of early crust formation and preservation.
“This suggests a significant change in the evolution of the Earth some four billion years ago, as meteorite bombardment waned, crust stabilised and life on Earth began to establish.”
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Drollner and his PhD supervisor and co-author Dr Milo Barham are both from the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences.
The research was published in the geology and earth science journal Terra Nova and Dr Barham said it was the first large-scale study of the region.
The piece of crust sits under the Yilgarn Craton that comprises a significant portion of of WA’s land mass and which is a rich source of valuable minerals – including gold, nickel, tantalum, iron ore, copper, zinc, platinum, vanadiun, titanium and lithium.
It’s estimated the “protocrust” could be as big as 100,000 square kilometres.
“The edge of the ancient piece of crust appears to define an important crustal boundary controlling where economically important minerals are found,” Dr Barham said.
“Recognising these ancient crustal remnants is important for the future of optimised sustainable resource exploration.
“Studying the early Earth is challenging given the enormity of time that has elapsed, but it has profound importance for understanding life’s significance 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’ can be found online here.