Rocks dating back 3.4 billion years from south-west Greenland’s Isua mountain range have yielded valuable information about the structure of Earth during its earliest stages of development. In these rocks, which witnessed the first billion years of Earth’s history, a French-Danish team led by researchers from the ‘Magmas and Volcanoes’ Laboratory (CNRS / Université Blaise Pascal / IRD) have highlighted a lack of neodymium-142, an essential chemical element for the study of Earth’s formation.
This deficit supports the hypothesis that between 100 and 200 million years after its formation, Earth was made up of an ocean of molten magma, which gradually cooled. The work, which was carried out in collaboration with the Laboratoire de Géologie de Lyon (CNRS / Université Lyon 1 / ENS de Lyon) and the University of Copenhagen, was published on 1 November 2012, in the journal Nature.
Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System. The heat produced by the accretion process, as well as by the decay of radioactive elements, caused this material to melt. As a result, 100 to 200 million years after its formation, Earth must have been made up of an ocean of molten magma, in the center of which a metallic core formed. The ocean gradually cooled. Earth’s crust then appeared, and the process of continental drift began. The crystallization of the molten magma is likely to have been accompanied by the chemical layering of Earth: concentric layers with distinct chemical compositions became differentiated. It is the signature of these primordial inhomogeneities that the researchers found in the Isua rocks.
Written By: CNRScontinue to source article at sciencedaily.com