Composition of Earth's mantle is different than previously thought: Study

A new study has helped researchers determine that the composition of Earth's lower mantle is quiet different than previously thought.

The work, performed at the Advanced Photon Source at the U.S. Department of Energy's Argonne National Laboratory, would have a significant impact on our understanding of the lower mantle. Understanding the composition of the mantle would be essential to seismology, and should shed light on unexplained seismic phenomena observed there.

The pressure and heat of the lower mantle is intense, more than 3,500 degrees Fahrenheit. Materials might have very different properties at these conditions; structures might exist there that would collapse at the surface.

The team found that at conditions that exist below about 1,200 miles underground, the ferromagnesian silicate perovskite actually breaks into two separate phases. One contains nearly no iron, while the other was full of iron. The iron-rich phase, called the H-phase, was much more stable under these conditions.

Scientist Li Zhang, Carnegie Institution of Washington, said that all geodynamic models need to be reconsidered to take the H-phase into account and there could be even more unidentified phases down there in the lower mantle as well, waiting to be identified.

Recent technological advances at the beamline allowed them to create the conditions to simulate these intense temperatures and pressures to probe the changes in chemistry and structure of the sample in situ.