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Bridgmanite identified as Earth's most abundant mineral

Scientists have identified and characterised a mineral that makes up 38 per cent of the Earth's volume and dubbed it Bridgmanite.


Bridgmanite identified as Earth's most abundant mineral

Washington: Scientists have identified and characterised a mineral that makes up 38 per cent of the Earth's volume and dubbed it Bridgmanite.

A team of scientists led by Oliver Tschauner, a mineralogist at the University of Las Vegas, has clarified the definition of the Earth's most abundant mineral - a high-density form of magnesium iron silicate, now named Bridgmanite.

Their research was performed at the Advanced Photon Source (APS), a US Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National Laboratory.

The mineral was named after 1964 Nobel laureate and pioneer of high-pressure research Percy Bridgman.

For decades, scientists have believed a dense perovskite structure makes up 38 per cent of the Earth's volume, and that the chemical and physical properties of Bridgmanite have a large influence on how elements and heat flow through the Earth's mantle.

But since the mineral failed to survive the trip to the surface, no one has been able to test and prove its existence - a requirement for getting a name by the International Mineralogical Association.

Shock-compression that occurs in collisions of asteroid bodies in the solar system creates the same hostile conditions of the deep Earth - roughly 2,100 degrees Celsius and pressures of about 240,000 times greater than sea-level air pressure.

The shock occurs fast enough to inhibit the Bridgmanite breakdown that takes place when it comes under lower pressure, such as the Earth's surface.

Part of the debris from these collisions falls on Earth as meteorites, with the Bridgmanite "frozen" within a shock-melt vein.

Previous tests on meteorites using transmission electron microscopy caused radiation damage to the samples and incomplete results.

So the team decided to try a new tactic: non-destructive micro-focused X-rays for diffraction analysis and novel fast-readout area-detector techniques.

Tschauner and his colleagues from Caltech and the GeoSoilEnviroCARS, a University of Chicago-operated X-ray beamline at the APS at Argonne National Laboratory, took advantage of the X-rays' high energy, which gives them the ability to penetrate the meteorite, and their intense brilliance, which leaves little of the radiation behind to cause damage.

The team examined a section of the highly shocked L-chondrite meteorite Tenham, which crashed in Australia in 1879.

The first natural specimen of Bridgmanite showed it contains an unexpectedly high amount of ferric iron, beyond that of synthetic samples. Natural Bridgmanite also contains much more sodium than most synthetic samples.

The results were published in the journal Science. 

From Zee News

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