Ancient supercontinent was a diamond factory

January 13th, 2009 - 2:20 pm ICT by ANI  

London, Jan 13 (ANI): A mineral exploration company has found diamonds, which are white and a few millimeters across, just outside the small village of Eurelia in Australia, which indicates that the ancient supercontinent was a diamond factory.

According to a report in New Scientist, after the discovery, the mineral exploration company sent the diamonds to Ralf Tappert, a diamond expert at the University of Adelaide.

Tappert and colleagues said that minerals found trapped inside the Eurelia diamonds could only have formed more than 670 kilometers (416 miles) beneath the surface of the Earth a distance greater than that between Boston and Washington, DC.

The vast majority of diamonds worldwide form at depths between 150 km and 250 km, within the mantle roots of ancient continental plates, said Tappert. These diamonds formed in the Earths lower mantle at depths greater than 670 km, which is much deeper than normal diamonds, he added.

Fewer than a dozen ultra-deep diamonds have been found in various corners of the globe since the 1990s. Sites range from Canada and Brazil to Africa and now Australia.

Deep diamonds are important because they are the only natural samples that we have from the lower mantle, said Catherine McCammon, a geologist at the University of Bayreuth in Germany.

This makes them an invaluable set of samples much like the lunar rocks are to our studies of the moon, she added.

The Eurelia gems contain information about the carbon they were made from. Their heavy carbon isotope signatures suggest the carbon was once contained in marine carbonates lying on the ocean floor.

Location, though, provides researchers with a common thread for the Brazilian, African and Australian deep diamonds, which could explain how they were born.

All six groups of diamonds were found in areas that would once have lined the edge of the ancient supercontinent Gondwana.

Deep diamonds have always been treated like oddball diamonds, said Tappert. We dont really know what their origin is. With the discovery of the ones in Australia, we start to get a pattern, he added.

Their geographic spread suggests that all these ultra-deep diamonds were formed in the same way.

As the oceanic crust dived down beneath Gondwana a process known as subduction it would have dragged carbon down to the lower mantle, transforming it into graphite and then diamond along the way.

Eventually, volcanic rocks known as kimberlites are propelled to the surface during rapid eruptions, bringing the gems up to the surface. (ANI)

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