Around four billion years ago, the temperature of Earth's mantle was so high that Archean crust formed in then would simply have melted back into the mantle, a new research has found.
Researchers at Institute of Geosciences at Johannes Gutenberg University Mainz (JGU) developed model calculations that helped in determining that the extreme density of the primary crust was the reason that caused it to recycle back into the mantle again.
They observed that the dense primary crust went to the mantle in drip form in a vertical pattern. The observations in the study however, contrasted with the mechanisms through which the modern tectonic plates primarily moved, which are lateral.
Investigators believe that because of the mantle's high temperature during the Archean eon, Earth's primary crust formed at that time would have been extremely thick and rich in magnesium.
"Furthermore, Archean crust exposed today is composed mostly of tonalite-trondhjemite-granodiorite (TTG), indicative of a hydrated, low-magnesium basalt source, suggesting that they were not directly generated from a magnesium-rich primary crust," wrote researchers.
The team of researchers led by Professor Richard White, created an ancient Earth crust and mantle model through computer simulations to show the conditions that prevailed during Archean era.
The model suggested that the base of the thickened and magnesium-laden crust would have been gravitationally unstable at mantle temperatures greater than 1,500 to 1,550 degree celsius. They expect the dense residues with high content of mafic minerals to reside in the mantle..
"The conclusion is that these pieces of crust cannot be the direct products of an originally magnesium-rich primary crust," researchers explained in the press release. "These TTG complexes are among the oldest features of our Earth's crust. They are most commonly present in cratons, the oldest and most stable cores of the current continents."
Developments of the study has been published in the online journal Nature Geoscience.
