AGU: Geophysical Research Letters

 

Editors' Highlight

Unsolved problems in the lowermost mantle

Observed within the deepest several hundred kilometers of the mantle, large anomalies in seismic velocities, called the D” layer, have come into recent scrutiny since scientists announced the discovery of a possible new high-temperature, high-pressure crystal packing structure transformed from the common mantle mineral perovskite. As new research emerges to synchronize this discovery with the current understanding of the lowermost mantle, Hirose et al. (2006) sought to list the important unsolved problems in mineral physics, seismology, and geodynamics that must first be addressed. Among other considerations, these questions involve the origin of the D” discontinuity; the determination of whether the D” layer is chemically heterogeneous, and if so, why; and the seismically inferred jump at this layer, which is too large in comparison to first-principles calculations. The authors expected that revealing the relative roles between phase transitions and chemical anomalies, though challenging, will prove critical to understanding the role of the D” layer in the thermal and chemical evolution of the Earth.

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