A new, clearer insight into the Earth’s hidden crystals

Geologians developed a new theory about the state of the earth billions of years ago after examining the very ancient rocks that formed in the earth’s mantle beneath the continents.

Assistant Professor Emma Tomlinson of Trinity College Dublin and Professor Balz Kamber, University of Technology, have just published their research in leading international journal, Nature communication.

The seven continents on earth today are built around a stable interior called a craton, and geologists believe that craton stabilization was critical about 2.5-3 billion years ago for the formation of land masses on Earth.

Little is known about the shape of cratons and their supporting mantle keels, but important clues can be found in peridotite xenolites, which are samples of mantles brought to the earth’s surface by erupting volcanoes.

Dr Tomlinson, of Trinity’s School of Natural Sciences, said:

“Many rocks of the mantle beneath ancient continents contain a surprising amount of silica – much more than is found in younger parts of the mantle.”

“There is currently no scientific consensus on the reason for this.”

The new research, which looks at the global data for mantle peridotite, comes with a new explanation for this observation.

The research used a new thermodynamic model to calculate that the unusual mineralogy developed when very hot molten rock – above 1700 ° C – interacted with older parts of the mantle, and this caused the growth of minerals with silica .

“For more than 1 billion years, from 3.8 to 2.5 billion years ago, volcanoes also erupted very unusual lavas with very low viscosity – lava that was very thin, very hot and often containing varying silica,” the dr. Tomlinson added.

“Our modeling suggests that the unusual lavas were in fact the molten rocks that cooperated at great depth with the mantle, and this interaction led to the changing level of silica.”

Professor Kamber, QUT, said:

“Both the silica-rich rocks in the deep mantle and the volcanic rocks with a low viscosity, ceased by the earth about 2.5 billion years ago. This timing is the boundary between the Archaic and Proterozoic centuries – one of the most important fractions in the geological nature of the Earth. time scale. “

What caused this boundary remains unknown, but the research offers a new perspective.

Professor Kamber added:

“This may be due to the change in the way the mantle flowed. Once the mantle began to slowly rotate to the core (2,900 km), the very high temperatures of the Archaic eon were no longer possible.”