Uncovering The Rock Record Of Earth’s Earliest Continental Crust

This study was led by Professor Jia Liu and Professor Qunke Xia from the School of Earth Sciences at Zhejiang University; researchers have taken a major step toward uncovering Earth’s missing geological history. The project, completed by PhD students Denggang Lu, Zhikang Luan, Jingjun Zhou, and Tianting Lei, sheds light on what the continental crust may have looked like during the Hadean eon—Earth’s earliest era, around 4.4 billion years ago.

“The Hadean is a key period for understanding the origin of Earth’s continents,” said Prof. Jia Liu. “But rocks from this time are incredibly rare. So far, the only known samples are from the Acasta region in Canada and date to about 4.03 billion years ago.” Due to intense geological activity in Earth’s early days, most rocks from that time have been destroyed, leaving behind what scientists call a “missing chapter” in Earth’s story.

However, one tiny but incredibly durable mineral has preserved clues: zircon. Some zircons are older than 4.3 billion years and are found in places like the Jack Hills in Australia. These ancient crystals record information about early magma activity.

“We don’t know what the actual rocks of the Hadean crust looked like, because we don’t have any—but zircons give us a window into that hidden world,” said PhD student Denggang Lu.

To unlock that window, the team compiled the world’s most comprehensive geochemical database to date of igneous zircon and their host rocks—more than 14,000 zircons and 823 matched rock records. Using this database, they trained supervised machine learning models to find patterns between trace elements in zircons and the chemical makeup of their host rocks. This allowed them to predict what the “missing” rocks might have looked like. It’s as if Earth’s earliest rocks had been brought back to life—virtually passed through modern instruments and revealed with chemical details, just like real samples tested in the lab.

“In an age of rapid AI development, using machine learning to uncover the relationship between zircons and their rocks is incredibly exciting,” said Prof. Liu. “It gives us a chance to push the known rock record back by nearly 400 million years and explore how the earliest crust may have evolved.”

The study suggests that the Hadean crust was likely formed through convergent tectonics—similar to what happens during continental collisions—rather than deep oceanic subduction. This points to early forms of plate convergence on the early Earth, offering a new model for primordial crust formation and introducing an innovative approach to studying Earth’s most ancient and elusive rocks. The method not only expands the potential of zircon in early Earth studies but also provides a significant breakthrough in uncovering the planet’s “missing geological chapters.”

This figure shows the temporal evolution of the chemical composition of Earth’s earliest continental crust, recovered from zircon data from Jack Hills Credit ©Science China Press

Earth’s Hadean crust formed via operation of convergent tectonics, National Science Review

Astrobiology, Astrogeology,