Ancient mantle revealed by 3.7-billion-year-old rocks in Australia

by Simon Mansfield
Sydney, Australia (SPX) Nov 06, 2025

Researchers at the University of Western Australia, along with colleagues from the University of Bristol, the Geological Survey of Western Australia, and Curtin University, examined feldspar crystals from anorthosite rocks found in the Murchison region of Western Australia. These rocks, dated at 3.7 billion years old, are confirmed to be the oldest on the Australian continent and among the earliest on Earth.

Lead author Matilda Boyce said the scarcity of ancient rocks makes determination of early crustal growth timing and rates challenging. The team applied fine-scale analytical methods to original plagioclase feldspar, capturing the isotopic composition of the ancient mantle.

The evidence revealed that continental crust formation began about 3.5 billion years ago, indicating continents grew later in Earth's history - around one billion years after the planet first formed.

Researchers compared their data with lunar anorthosites collected during NASA's Apollo missions. Boyce noted that while anorthosites are rare on Earth, they are prevalent on the Moon. Their analyses showed that both Earth and Moon share a starting composition date of around 4.5 billion years ago, supporting the impact theory for the Moon's origin.

Funding for the project was provided by the Australian Research Council.

Research Report:Coupled strontium-calcium isotopes in Archean anorthosites reveal a late start for mantle depletion

Related Links
The University of Western Australia
Explore The Early Earth at TerraDaily.com