Analysis of feldspar crystals found in Australia's oldest magmatic rocks provides special information about the early formation of the Moon and the Earth's ancient continents and mantle.
According to a statement issued Monday, November 3, by the University of Western Australia (UWA), scientists studied 3.7-billion-year-old anorthosites from the Murchison region of the state of Western Australia, which are among the oldest rocks on Earth and the oldest on the Australian continent.
UWA PhD student Matilda Boyce, lead author of the study published in Nature Communications, said, "The timing and rate of early crustal growth on Earth remains contentious due to the scarcity of very ancient rocks."
Boyce, who worked with the Geological Survey of Western Australia, Australia's Curtin University, and Britain's University of Bristol, said that researchers employed fine-scale analytical techniques to separate the new regions of plagioclase feldspar crystals, which document the isotopic "fingerprint" of the ancient mantle.
According to their research, the continents started to expand about 3.5 billion years ago, or one billion years after the planet formed, which is a relatively late time in Earth's history.
Measurements of lunar anorthosites, which are uncommon rocks on Earth but extremely common on the Moon, were also used to compare the findings.
"Our comparison was consistent with the Earth and Moon having the same starting composition of around 4.5 billion years ago," Boyce said, adding, "This supports the theory that a planet collided with early Earth and the high-energy impact resulted in the formation of the Moon."
