Chinese scientists have analyzed the composition of the oldest zircons using machine learning. These minerals store information about the processes in the bowels of the planet. According to the authors of the new study, everything indicates that the movement of plates in the lithosphere has already occurred in Katarchea.

According to modern ideas, the Earth’s appearance is determined by the dynamics of its solid shell (lithosphere). It is divided into horizontally moving plates. When they collide, they crinkle, bend, slide under each other and descend into the mantle.

It is not known exactly when this process began. One of the most recent estimates – 3.6 billion years – was derived from the analysis of zircons. These silicate minerals preserve information about the composition of the parent igneous melt, even if the rocks are later reprocessed.

The oldest zircons (4.2 billion years old) were discovered in the Jack Hills region of Western Australia. Geologists call this time a comforting one. At that time, the Earth was still very hot, magma was rising to the surface, there was no atmosphere, and the thin crust of the planet was bombarded by comets and asteroids.

No catarrhal rocks are preserved, only zircons. According to chemical composition, they are divided into two types, by analogy with granites – I and S. The first was formed in the presence of real mantle melts, the second in the presence of material, mostly sedimentary, coming from the surface. Thus, S-zircons indicate the existence of continents and chemical weathering, and therefore plate tectonics.

Some experts doubted the existence of plate movements in the catarrhal. It is believed that this mechanism arose later, when the Earth’s crust hardened and thickened. The debate on this issue continues. To allow this, it is necessary to analyze all available data on the composition of detrital zircons and the ratio of chemical elements in them.

Scientists from the Chinese Academy of Sciences, together with colleagues from Canada and the US, used artificial intelligence to do this. They trained the model on 374 detrital zircon samples of known origin. Convinced that it had correctly identified both types of minerals, the researchers applied it to classify 971 zircons of Catarchean age.

Note that attempts have already been made to create classifiers for zircons, but the authors of the new study are confident that their model is the most accurate. More than a third of the zircons from Jack Hills turned out to be of the S type. A similar relationship is observed for minerals recently found in the Green Sandstone in South Africa. So the phenomenon is more common than previously thought.

The authors of the article summarized: “This shows conclusively that S-type granite masses and their accompanying sedimentary rocks already existed on Earth at least 4.2 billion years ago.”

The earliest reliable dates for S-type granites are 3.55 billion years, and for sedimentary rocks, 3.95 billion years. In the new study, their ages are shifted significantly to the left.

Scientists noted that almost half of Qatari zircons are of the S type. However, their proportions change over time. According to the authors, this reflects the cycle of creation and disintegration of supercontinents. In the interview Science Jun Korenaga, a geophysicist at Yale University who also models the onset of plate tectonics, called it “pure speculation.”

“If subduction (the sinking of one lithospheric plate beneath another) was present more than four billion years ago, this does not mean that the plate tectonic mechanism was fully activated,” said Chris Hawksworth, a geochemist at the University of Bristol. “The impact of a giant asteroid could have pushed the crust into the mantle,” the researcher stressed.

With all this, there is more and more evidence for the early onset of lithospheric plate movements. And the new scientific study is another argument “in its favor.”