Scientists discover unexpected atomic properties of materials in Earths lowermost mantle

September 17th, 2008 - 3:21 pm ICT by ANI  

Washington, September 17 (ANI): A team of researchers has discovered that materials deep inside Earth have unexpected atomic properties that might force earth scientists to revise their models of Earths internal processes.

A team of scientists led by Jung-Fu Lin at The University of Texas at Austins Jackson School of Geosciences recreated in the lab the materials, crushing pressures and infernal temperatures they believe exist in the lowermost mantle, nearly 2,900 kilometers (1,800 miles) below Earths surface.

According to the researchers, the materials exhibit rare and unexpected atomic properties that might influence how heat is transferred within Earths mantle, how columns of hot rock called superplumes form, and how the magnetic field and heat generated in Earths core travel to the planets surface.

The planetary building blocks magnesium, silicon, oxygen and iron are the most abundant minerals in the lowermost mantle.

Jung-Fu Lin and his team synthesized materials from these building blocks in a diamond anvil cell, a device containing two interlocking diamond pieces that squeeze the sample like a vice.

They subjected the sample to more than 1.3 million times standard atmospheric pressure.

Shining a laser through the transparent diamonds, they then heated the sample to almost 3,000 degrees Celsius (5,400 degrees Fahrenheit) for several days.

The scientists used a facility at Argonne National Laboratory called a synchrotron light source, to reveal the samples electronic and atomic structure.

They determined that the high pressures had caused some of the electrons in the samples iron, which normally repel each other, to pair up or become bound to each other.

This was the first evidence of a broad region in the subsurface with what scientists describe as intermediate-spin state, or partially paired iron electrons.

We were surprised to find partially paired electrons, said Lin. That doesnt normally occur in other geological materials that we know about, he added.

The degree of electron pairing, also known as electronic spin state, can affect how well the materials conduct heat and electricity.

According to Lin, modelers who make computer simulations of mantle dynamics will now have to go back and try to determine how this intermediate-spin state might affect the way heat is transferred within Earth, how superplumes form, how convection occurs in the mantle and how Earths magnetic field might radiate from the core.

The electronic spin state can also affect the speed of seismic waves traveling through material in the deep mantle.

As a result, seismic images of the lowermost mantlecollected when earthquake vibrations travel through and reflect off of material in the subsurfacemay have to be reinterpreted. (ANI)

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