Bullen's Parameter as a Seismic Observable for Spin Crossovers in the Lower Mantle

  title={Bullen's Parameter as a Seismic Observable for Spin Crossovers in the Lower Mantle},
  author={Juan J Valencia-Cardona and Quentin Williams and Gaurav Shukla and Renata M. Wentzcovitch},
  journal={Geophysical Research Letters},
  pages={9314 - 9320}
Elastic anomalies produced by the spin crossover in ferropericlase have been documented by both first‐principles calculations and high pressure‐temperature experiments. The predicted signature of this spin crossover in the lower mantle is, however, subtle and difficult to geophysically observe within the mantle. Indeed, global seismic anomalies associated with spin transitions have not yet been recognized in seismologic studies of the deep mantle. A sensitive seismic parameter is needed to… 
1 Citation

Spin Crossover in Ferropericlase at High Pressure: A Seismologically Transparent Transition?

The pressure-induced iron spin state transition in the lower mantle may influence seismic wave velocities by changing the elasticity of iron-bearing minerals, but no seismological evidence of an anomaly exists.

Spin crossover in ferropericlase and velocity heterogeneities in the lower mantle

It is shown that a spin state change in iron in ferropericlase produces seismic velocity anomalies that can be misinterpreted as compositional heterogeneity, and the one-of-a-kind signature of this spin crossover in the RS/P heterogeneity ratio might be a useful fingerprint to detect the presence of Fp in the lower mantle.

Elastic anomalies in a spin-crossover system: ferropericlase at lower mantle conditions.

A formulation for thermoelasticity of spin crossover systems is introduced, applied to Fp by combining it with predictive first principles density-functional theory with on-site repulsion parameter U calculations, and results are compared with available data on samples with various iron concentrations.

Iron Partitioning and Density Changes of Pyrolite in Earth’s Lower Mantle

Using a multianvil apparatus to study a synthetic material similar in composition to the lower mantle, Irifune et al. demonstrate that the spin transition occurs at lower pressures, and thus shallower depth, than suggested by earlier studies based on simpler compositions, and the observed density profile agrees well with seismological models, which suggests that pyrolite is a good model composition for the upper to middle parts of theLower mantle.

Bullen’s parameter η: a link between seismology and geodynamical modelling

Elasticity of (Mg,Fe)O Through the Spin Transition of Iron in the Lower Mantle

The complete elastic tensor of ferropericlase was measured through the spin transition of iron, whereupon the elastic moduli exhibited up to 25% softening over an extended pressure range from 40 to 60 gigapascals, fully consistent with a simple thermodynamic description of the transition.

Influence of the iron spin crossover in ferropericlase on the lower mantle geotherm

The iron spin crossover in ferropericlase introduces anomalies in its thermodynamics and thermoelastic properties. Here we investigate how these anomalies can affect the lower mantle geotherm using

Profiles of the Bullen parameter from mantle convection modelling