An analysis of feldspar crystals within the oldest magmatic rocks in Australia has provided a unique insight into Earth's ancient mantle and continents, and the early beginnings of the Moon.
Lead author and PhD student Matilda Boyce collaborated with researchers from UWA's School of Earth and Oceans, the University of Bristol, the Geological Survey of Western Australia and Curtin University on the study published in Nature Communications.
Researchers examined 3.7-billion-year-old anorthosites from the Murchison region of Western Australia – the oldest rocks on the Australian continent and some of the oldest rocks on Earth.
"The timing and rate of early crustal growth on Earth remains contentious due to the scarcity of very ancient rocks," Ms Boyce said.
"We used fine-scale analytical methods to isolate the fresh areas of plagioclase feldspar crystals, which record the isotopic 'fingerprint' of the ancient mantle."
The results 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 collected during NASA's Apollo program.
"Anorthosites are rare rocks on Earth but very common on the Moon," Ms Boyce said.
"Our comparison was consistent with the Earth and Moon having the same starting composition of around 4.5 billion years ago.
"This supports the theory that a planet collided with early Earth and the high-energy impact resulted in the formation of the Moon."
The research was funded by the Australian Research Council.
