title: Spin crossover in ferropericlase at high pressure: a seismologically transparent transition?
abstract: Seismic discontinuities in Earth typically arise from structural, chemical, or temperature variations with increasing depth. 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. Inelastic x-ray scattering measurements on (Mg(0.83)Fe(0.17))O-ferropericlase at pressures across the spin transition show effects limited to the only shear moduli of the elastic tensor. This explains the absence of deviation in the aggregate seismic velocities and, thus, the lack of a one-dimensional seismic signature of the spin crossover. The spin state transition does, however, influence shear anisotropy of ferropericlase and should contribute to the seismic shear wave anisotropy of the lower mantle.
authors.affiliation: Institut de Minéralogie et de Physique des Milieux Condensés, UMR CNRS 7590, Institut de Physique du Globe de Paris, Université Pierre et Marie Curie, Université Paris Diderot, 75005 Paris, France. daniele.antonangeli@impmc.upmc.fr
authors.forename: Daniele
authors.initials: D
authors.lastname: Antonangeli
authors.forename: Julien
authors.initials: J
authors.lastname: Siebert
authors.forename: Chantel M
authors.initials: CM
authors.lastname: Aracne
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Farber
authors.forename: A
authors.initials: A
authors.lastname: Bosak
authors.forename: M
authors.initials: M
authors.lastname: Hoesch
authors.forename: M
authors.initials: M
authors.lastname: Krisch
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Ryerson
authors.forename: Guillaume
authors.initials: G
authors.lastname: Fiquet
authors.forename: James
authors.initials: J
authors.lastname: Badro