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Although the world is 4.54 billion years old, the rocks are not. The many processes that shape the earth's crust and the highest levels of our planet are constantly changing these rocks: they form, they grow, break, turn into dust and convert back to rocks.
Some of Earth's oldest rocks have persisted for about 4 billion years, but researchers believe that they have now discovered evidence of something much older. The super-diamonds found in Brazil allude to a rock reservoir located at least 410 kilometers below sea level, which could be a few tens of millions of years younger than the Earth itself. The study is published in the journal Science.
During its formative years, the Earth has experienced violent volcanism and enormous geological changes. He also collided with an object the size of Mars, which threw so much material into orbit that half became the Moon we all know and love today. There are very few original rocks left on Earth, but the reservoir does not seem to have been disturbed since the formation of the planet.
Since the 1980s, scientists have found clues that something deep in the mantle was much older. When they compared the amount of helium-4 and helium-3, they found that the ratio of these elements was closer to what we see in ancient meteorites than that of we are watching on Earth today. Scientists also looked at chemical clues trapped in super-deep diamonds and found support for the idea of an unchanging ancient material at the bottom of the earth's crust.
"Diamonds are the hardest and most indestructible natural substance known. They therefore form a perfect time capsule that provides us with a window on the deep Earth. We were able to extract helium gas from twenty-three super-deep diamonds from the Juina region of Brazil. These have shown the characteristic isotopic composition expected from a very old reservoir, "said in a statement Dr. Suzette Timmerman, head of research at the Australian National University.
"From the geochemistry of diamonds, we know that they have formed in a region called transition zonewhich lies between 410 and 660 kilometers below the surface of the Earth. This means that this invisible reservoir, left since the beginning of the Earth, must be in this zone or below. "
Research is a first step in understanding what a tank looks like. It is still unclear whether there is one large reservoir or several small ones. Its chemical composition is also unknown, but finding the oldest undisturbed material on Earth is definitely intriguing.
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