News – AU – A new, clearer look into the hidden crystals of the earth

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PICTURE: A transmitted light view through a 200 micron section of a peridotite sample showing the three main minerals – olivine (clear-green), orthopyroxene (gray-green), and garnet (pink)

Geologists developed a new theory about the state of the earth billions of years ago after studying the very ancient rocks that formed in the mantle beneath the continents

Assistant Professor Emma Tomlinson from Trinity College Dublin and Professor Balz Kamber from Queensland University of Technology have just published their research in the leading international journal Nature Communications

The seven continents on earth today are each built around a stable interior known as a craton, and geologists believe that craton stabilization is around 2, 5 – 3 billion years ago was crucial in the formation of land masses on Earth

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

“Many rocks from the mantle under ancient continents contain surprisingly high amounts of silica – much more than in younger parts of the mantle”

The new study looking at the global data for mantle peridotite provides 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 silica-rich minerals

“For more than 1 billion years from 38 to 2.5 billion years ago, volcanoes also erupted very unusual, very low viscosity lavas – lava that was very thin, very hot, and often contained varying amounts of silica,” added Dr Tomlinson added

“Our modeling suggests that the unusual lavas were in fact molten rocks that interacted with the mantle at great depths, and that interaction resulted in variable levels of silica”

“Both the silica-rich rocks in the deep mantle and the low-viscosity volcanic rocks were no longer produced by the earth 5 billion years ago. This timing is the boundary between the Archaic and the Proterozoic Ages – one of the most significant breaks in the geological time scale of the earth “

“This could be due to a change in the flow of the mantle. As soon as the mantle slowly moves to the core (2nd900 km), the very high temperatures of the archaic eon were no longer possible “”

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Earth, Peridotite, Kraton, Mineral, Geology, Balz Kamber

News – AU – A new, clearer insight into the hidden crystals of the earth
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Source: https://www.sciencecodex.com/new-clearer-insight-earths-hidden-crystals-667218