Impurities in diamonds unravel earth’s turbulent past

July 24th, 2011 - 3:49 pm ICT by IANS  

Washington, July 24 (IANS) Jewellers abhor impurities in diamonds, but scientists say they provides clues that unravel the turbulent period of our planetary past.

Researchers analysed data of over 4,000 of these impurities in diamonds (mineral inclusions) to find that continents started the cycle of breaking apart, drifting, and colliding about three billion years ago, when the so-called Wilson cycle began.

Steven Shirey from the Carnegie Institution’s Department of Terrestrial Magnetism explained: “The Wilson cycle is responsible for the growth of the Earth’s continental crust, the continental structures we see today…”

“But when it all began has remained elusive until now. We used the impurities, or inclusions, contained in diamonds, because they are perfect time capsules from great depth beneath the continents,” said Shirey, who led the study, the journal Science reports.

“They provide age and chemical information for a span of more than 3.5 billion years that includes the evolution of the atmosphere, the growth of the continental crust, and the beginning of plate tectonics,” Shirey concluded, according to a Carnegie statement.

Co-author and longtime colleague Stephen Richardson of the University of Cape Town added: “It is astonishing that we can use the smallest mineral grains that can be analysed to reveal the origin of some of Earth’s largest geological features.”

The largest diamonds come from cratons, the most ancient formations within continental interiors that have deep mantle roots or keels around which younger continental material gathered.

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