title: Spin and valence dependence of iron partitioning in Earth's deep mantle.
abstract: We performed laser-heated diamond anvil cell experiments combined with state-of-the-art electron microanalysis (focused ion beam and aberration-corrected transmission electron microscopy) to study the distribution and valence of iron in Earth's lower mantle as a function of depth and composition. Our data reconcile the apparently discrepant existing dataset, by clarifying the effects of spin (high/low) and valence (ferrous/ferric) states on iron partitioning in the deep mantle. In aluminum-bearing compositions relevant to Earth's mantle, iron concentration in silicates drops above 70 GPa before increasing up to 110 GPa with a minimum at 85 GPa; it then dramatically drops in the postperovskite stability field above 116 GPa. This compositional variation should strengthen the lowermost mantle between 1,800 km depth and 2,000 km depth, and weaken it between 2,000 km depth and the D" layer. The succession of layers could dynamically decouple the mantle above 2,000 km from the lowermost mantle, and provide a rheological basis for the stabilization and nonentrainment of large low-shear-velocity provinces below that depth.
authors.affiliation: Earth and Planetary Science Laboratory, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; helene.piet@epfl.ch.
authors.forename: Hélène
authors.initials: H
authors.lastname: Piet
authors.affiliation: Earth and Planetary Science Laboratory, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; Institut de Physique du Globe de Paris, Sorbonne Paris Cité, CNRS, FR-75005 Paris, France.
authors.forename: James
authors.initials: J
authors.lastname: Badro
authors.affiliation: Earth and Planetary Science Laboratory, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; Centre Interdisciplinaire de Microscopie Électronique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Farhang
authors.initials: F
authors.lastname: Nabiei
authors.affiliation: Centre Interdisciplinaire de Microscopie Électronique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; Laboratoire de Spectrométrie et Microscopie Électronique, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Teresa
authors.initials: T
authors.lastname: Dennenwaldt
authors.affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281.
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Shim
authors.affiliation: Centre Interdisciplinaire de Microscopie Électronique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Cantoni
authors.affiliation: Centre Interdisciplinaire de Microscopie Électronique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; Laboratoire de Spectrométrie et Microscopie Électronique, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Cécile
authors.initials: C
authors.lastname: Hébert
authors.affiliation: Earth and Planetary Science Laboratory, Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Gillet
keywords: iron partitioning; lower mantle; spin state; valence state; viscosity