SYDNEY, Nov. 3 (Xinhua) -- The analysis of feldspar crystals in Australia's oldest magmatic rocks reveals unique insights into Earth's ancient mantle and continents, as well as the early formation of the Moon.
Researchers examined 3.7-billion-year-old anorthosites from the Murchison region of the state of Western Australia, the oldest rocks on the Australian continent and some of the oldest rocks on Earth, according to a statement released Monday by the University of Western Australia (UWA).
"The timing and rate of early crustal growth on Earth remains contentious due to the scarcity of very ancient rocks," said UWA PhD student Matilda Boyce, lead author of the study published in Nature Communications.
Researchers used fine-scale analytical methods to isolate the fresh areas of plagioclase feldspar crystals, which record the isotopic "fingerprint" of the ancient mantle, said Boyce, who collaborated with Australia's Curtin University, the Geological Survey of Western Australia, and Britain's University of Bristol.
Their findings suggested the continents began to grow relatively late in Earth's history, from around 3.5 billion years ago, which is one billion years after the planet formed.
The study also compared the results with measurements of lunar anorthosites, which are rare rocks on Earth but very common on the Moon.
"Our comparison was consistent with the Earth and Moon having the same starting composition of around 4.5 billion years ago," Boyce said. "This supports the theory that a planet collided with early Earth and the high-energy impact resulted in the formation of the Moon." ■