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In the first billion years of Earth’s 4.5 billion year history, a study has found that continents were formed by meteorite impacts. Tim Johnson, a research team at Curtin University’s Earth Science Institute (TIGER) in Australia, published the results of this study in the international scientific journal Nature on the 11th.
The research team analyzed the oxygen isotopes of zirconium among minerals extracted from ingots in Pilbara, Australia, where the remains of ancient crust are best preserved. An ingot is a stable continental crust that has not undergone severe tectonic fluctuations since the Cambrian. The Pilbara region, located in Western Australia, is considered to be the place with the oldest traces of life on Earth, including fossils of living creatures that were found about 3.6 billion years ago.
The zirconium in this region is estimated to have formed 2.5 to 4 billion years ago and consisted of three layers. In the oldest layers, traces of magma formed by the melting of the Earth’s mantle in a huge impact have been found. The mantle is a thick layer of rock that surrounds the Earth’s core beneath the crust.
In the second layer, quartz crystals formed by cooling of the magma formed in this way were found. In the layer closest to the surface, flossite, a rock formed by magma solidifying over a long period of time, was discovered.
“It is no coincidence that old felsic rocks were found on the surface of zirconium,” the research team said. A similar oxygen isotope composition was found in ancient continental crust found in other parts of the planet, the team added.
“As the Earth’s continents have evolved, various mineral resources have been deposited,” said Johnson, who led the study.
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