Scientists have just published a discovery It could change the current view of how tectonic plates work. south of africa They found the oldest rocks, 2.7 billion years old, found on the seafloor., it also appears to originate from the neighboring African continent. They didn’t expect to find stones of this age in a relatively young place: “It’s like finding a mother in kindergarten,” say researchers from the Chinese Academy of Sciences.
Between the Earth’s solid tectonic plates and the convective mantle lies a warm, soft layer known as the asthenosphere, varying between 40 and 660 kilometers in depth. At mid-ocean ridges, basalt from the warm asthenosphere rises to the surface of the seafloor.forming new oceanic crust and regenerating the seafloor.
Over time, this new oceanic crust ages, cools, and becomes denser. But When this material encounters an obstacle, such as a continent, it sinks underneath, thus returning matter from below to melt in the asthenosphere and return it to the mantle. deeper, a phenomenon known as subduction. Therefore, oceanic crust is typically not older than 200 million years.
However, something was found that did not fit. A joint research team led by Professor Liu Chuanzhou from the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGG), He found abyssal peridotites from the seafloor along the southwestern ridge of the Indian Ocean, especially south of Madagascar.. This is a surprise because they are the oldest rocks ever discovered in the ocean. A later study actually comes from the neighboring African continent. This study has been published Science Advances this is so many weeks.
These newly discovered rocks in the Indian Ocean are 2.7 billion years old and date back to a period that geologists call “Archaean,” from the Greek word for “ancient.” They’re too old to be there. To use an analogy, the emergence of these ancient rocks on a young mid-ocean ridge is “like finding a mother in a kindergarten,” according to scientists. These incredibly ancient mid-ocean ridge rocks offer a clue to their mysterious origins.
Continental rocks, not ocean floor
Also, these ancient rocks have strongly refractory compositions; In geochemistry, refractory refers to a lack of soluble (i.e., easily soluble) components in the mantle. Then, They look less like the stuff in the oceans and more like the rocks that make up the continents.
How is this possible? According to the authors of the work, the only explanation for this is: These rocks from the archaeal mantle of the Indian Ocean would have broken off and transported more than 2,000 km to the mid-ocean ridge via the asthenosphere. where they were discovered.
Computer simulations were performed to test whether this geological recycling mechanism was actually valid. And really, The results obtained show that this recycling process is quite efficient. In fact, up to 20% of the continent can be submerged in just 100 million years, which from a geological perspective is a blink of an eye.
Ancient continental debris found on the ocean floor clearly shows that oceanic plates have a more complex function than previously thought Previously.
“Therefore, to decipher Earth’s evolution, more attention should be paid to the bottom of the oceanCovering three-fifths of the Earth’s surface,” the researchers explained.
The work was carried out in collaboration with the Woods Hole Institution of Oceanography and the Max-Planck Institut fur Chemie.
Reference research: https://www.science.org/doi/10.1126/sciadv.abn6749
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