Rocks in Canada may be oldest on Earth, dating back 4.16 billion years
An obscure rock formation on the eastern bank of Canada Hudson Bay can contain the oldest known rocks on the earth, affirms a new study.
The analysis dated from the striated gray rocks of the site, which is part of an outcrop called the green stone belt Nuvvuactuq, to 4.16 billion years – which means that they are remains of the first crust of the planet of 4.57 billion billions of planets.
The dating, carried out by two methods which used the decrease of the radioactive isotopes (versions of elements) to measure the age of the old magma trapped inside the rocks, strengthens considerably A controversial previous study by the same scientists.
If their conclusions, published on June 26 in the journal ScienceStanding, they could offer a unique window on the ancient history of our planet and the geochemical stadium where life has emerged.
“Volcanic rocks must have at least 4.16 billion years or more; I would say that the best age for them is 4.3 billion years,” said the co-author of the study Jonathan O’NeilProfessor of environmental sciences at the University of Ottawa, told Live Science. “No known rock is older.”
The earth started like a red -heated lava ball. It has slowly cooled during its first 600 million years, known as Hadean Eon, when pockets of solid rock began to form. It was a tumultuous period for our young planet, which was hit several times by asteroids and even underwent a cataclysmic blow of the Protoplanet Theia, which torn a piece of earth To train our moon.
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So, as 3.8 billion years agoThe surface of the earth broke out in tectonic plates, which plunged each other to be recycled inside the earth or to build large mountain ranges or trenches. This subduction means that many rocks on the surface of our planet have long been chemically changed by intense heat and pressure.
However, some regions are far enough from the limits of tectonic plates to contain rocks that have remained unchanged for billions of years. One of them is in northeast Canada, and its oldest part is the Greenstone Nuvvuactuq belt (NGB). Scientists agree that this outcrop has at least 3.8 billion years.
Then, in 2008, O’Neil and his colleagues published a study suggesting that the NGB was 4.3 billion years – which would mean that it contained the oldest rocks in the world.
But other geologists opposed, suggesting that there were defects in the methods of researchers. The old rocks are generally dated using a mineral called Zircon, which is chemically stable over billions of years. The volcanic rocks of the NGB, however, do not contain zircon, which forced scientists to measure the age of the rocks by the decrease of the Samarium element in the neodymium.
However, the problems were hidden in this new method. Samarium can decompose in the neodymium through two ways (Samarium-146 in the neodymium-142, or Samarium-147 in the neodymium-143), creating two isotopic clocks with different disintegration speeds. The first disintegration path leads to a half -life – the time period required for half of the original element to stay – of around 96 million years, while the second route has a half -life covering billions of years.
This means that the two decrease paths have produced extremely different estimates for the ages of the rocks. Indeed, with the longer lifespan clock at the present day, it is particularly sensitive to tectonic events mudding its isotopes halfway from the disintegration process.
“Any” cuisine “of rocks or metamorphism after 4 billion years will not really affect this short clock, but can reset the long lifespan clock and cause the age difference between these two systems,” said O’Neil.
To get around this problem, the team returned to training to search for sections where the magma of the Earth’s mantle, or intermediate layer, intrusion into the primordial crust of the planet. Because these intrusions had to be younger than the rock in which they infiltrated, they could be used at the minimum age. The new analysis revealed that in these sections of the NGB, the two samarium disinterested in neodymium offered the same age: 4.16 billion years.
If additional research confirms that the rocks are as old as the O’Neil team believes, they could offer an essential overview of the way life has emerged on our planet and potentially beyond.
“Some rocks of the green stone belt Nuvvuactuq have been formed by precipitation of sea water, and they can help understand the composition of our first oceans, their temperature, perhaps the atmosphere and could also accommodate the oldest traces of life on earth,” said O’Neil. “Understanding the environment where life could have started on our planet also helps in our quest to find traces of life elsewhere, like Mars.”
