The oldest fragments of terrestrial crust discovered in Québec: they date back to over 4 billion years ago and tell when the earth was an infernal environment.
The land was born about 4.6 billion years ago, in an era of its history known as Eone Adoano, from the name of the Greek god of the underworld, Hades. This mythological reference reflects The infernal environment of our primordial planet: extreme temperatures, constantly eruption volcanoes, impacts with meteorites and an oxygen -free atmosphere.
According to current estimates, already 4.35 billion years ago the earth’s surface could have started to cool downallowing the formation of a primitive crust and, perhaps, the appearance of the first habitable environments. This initial phase of Earth’s history, however, is still wrapped in mystery. The geological testimonies of the Adoan Ethic are very rare: most of the rocks of that period was destroyed or transformed over the billions of years by numerous geological events, canceling almost completely the traces of the past.
The oldest rocks on the earth. An international team of researchers, which also includes Canadian and French scientists, has recently confirmed that some of the oldest rocks known in the world are found in the north of Québecin the remote belt of green rocks of NuletaGittittittittittuq, in the Nunavik region, north of the 55th parallel. These rock formations date back to Over 4 billion years ago and constitute an extraordinary window on the geological past of the earth.
In particular, the most common rocks in the nursing belt are known as Rocce Ujaraaluk – a term in Inuktitut language which means “large ancient and solid rock”. It is Metamorphic volcanic rocks (i.e. rocks that have undergone profound transformations related to high temperatures and pressures), rich in magnesium and iron, characteristics of a primordial terrestrial crust, perhaps similar to that which today is observed in the ocean seabed.
a matter of age. The possibility that these rocks belong toAeon Adean He was hypothesized for the first time in 2008 by Jonathan O’Neil, today associate professor and then learning to McGill University. O’Neil and colleagues pointed out in the rocks of NuletaGittittittittittittuq variations in the Neodimio-142 isotope, produced exclusively during the Ademan from the radioactive decay of the Samario-146.
This method had so far been used only to date meteorites and lunar rocks, but never successfully applied to terrestrial champions. According to this isotopic dating, some rocks of the belt would have an age of about 4.3 billion yearsmaking them potentially the oldest ever identified on earth. However, this hypothesis was not accepted without criticism. Some subsequent studies, analyzing zircon crystals found in the same rocks, have proposed a younger age, around 3.78 billion years, thus placing them in the next heine, the Archean.
New tests. In an attempt to solve this scientific dispute, in the summer of 2017 the team returned to the place to collect new champions, focusing on intrusive rocks – calls Metagabbri – that cross the formations of Ujaraaluk. These intrusions, being geologically younger than the rocks that cross, offer a fundamental temporal reference.
The field work was led by Chris Sole, then a masterful student at the University of Ottawa, together with Jean-Louis Paquette, French geocronologist expert in isotopic dating, and two university students, David Benn (University of Ottawa) and Joeli Plakholm (University of Carleton). Through an in -depth analysis of petrology, geochemistry and geochronology, whose results have been published on Sciencethe team applied Two independent dating methods based on the Samario-Eodimio systemmanaging to establish a precise age for metagabbris: 4.16 billion years. Since these rocky bodies sink into the rocks of Ujaraaluk, it is certain that the basic rocks are even older – by definitively placing them inside the Ademano.
The secrets of the zirconi. Outside the québec, the only other traces of the Avana area come from tiny but resistant minerals: the zirconi found in Western Australia, dating back to about 4.4 billion years ago. Although the guest rocks have been destroyed, these zirconi survived intact, offering precious indications on the environment of the time.
The chemical analysis of these crystals suggests that They were formed in magicians derived from ocean sediments, to indicate the presence of liquid water on the earth’s surface already these days. Some research speculate that the oceans formed just 150 million years after the birth of the planet. In addition, the zirconi suggest that the first terrestrial crust was of the mafic type (rich in iron and magnesium), similar to that of modern oceanic funds, but so far its existence has only remained hypothetical. The rocks of Nuletagittittittuq could represent the concrete testimony of this lost crust.
