Shown that the continental crust arose 500 million years earlier than expected

Shown that the continental crust arose 500 million years earlier than expected
Shown that the continental crust arose 500 million years earlier than expected
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Scientists have found that the continental crust formed half a billion years earlier than previously thought. This is critical to understanding the processes of plate tectonics and biological evolution.

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The results of the study were presented at the EGU General Assembly 2021. The appearance of the continental crust during the Archean period (from four to 2.5 billion years ago) is important for understanding the subsequent tectonics of lithospheric plates, ocean chemistry and biological evolution.

After all, when the continental parts become stable, they begin to erode and "add" important minerals and nutrients to the ocean. It is not known exactly at what period stable continental parts appeared on Earth, since few such ancient rocks have survived, and the composition of rocks that are older than three billion years has changed under the influence of time.

Scientists from the University of Bergen (Norway), the Institute of Geology and Paleontology (Germany) and the University of Utrecht (the Netherlands) have shown that weathering changed the strontium isotopic composition in Archean seawater. To do this, experts have applied a new approach using the mineral barite.

It is formed from a combination of sulphate from ocean water and then mixed with barium from hydrothermal vents. At the same time, barite has a reliable record of the chemical composition of the ocean in its structure, so its composition does not differ from what it was 3.5 billion years ago.

As a result, scientists tested six barite deposits on three different continental parts with an age ranging from 3.2 to 3.5 billion years ago. They calculated the ratio of strontium isotopes in barite, and then concluded when the weathered continental rock entered the ocean and turned into barite. It turned out that weathering began about 3.7 billion years ago, that is, about 500 million years earlier than previously thought. This significantly affects our knowledge of how life originated and developed.

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