Letter abstract
Nature Geoscience 1, 684 - 687 (2008)
Published online: 14 September 2008 | doi:10.1038/ngeo309
Subject Categories: Structural geology, tectonics and geodynamics | Volcanology, mineralogy and petrology
Stable intermediate-spin ferrous iron in lower-mantle perovskite
C. McCammon1, I. Kantor1,4, O. Narygina1, J. Rouquette1,4, U. Ponkratz2, I. Sergueev2, M. Mezouar2, V. Prakapenka3 & L. Dubrovinsky1
The lower mantle is dominated by a magnesium- and iron-bearing mineral with the perovskite structure. Iron has the ability to adopt different electronic configurations, and transitions in its spin state in the lower mantle can significantly influence mantle properties and dynamics. However, previous studies aimed at understanding these transitions have provided conflicting results1, 2, 3, 4. Here we report the results of high-pressure (up to 110 GPa) and high-temperature (up to 1,000 K) experiments aimed at understanding spin transitions of iron in perovskite at lower-mantle conditions. Our Mössbauer and nuclear forward scattering data for two lower-mantle perovskite compositions demonstrate that the transition of ferrous iron from the high-spin to the intermediate-spin state occurs at approximately 30 GPa, and that high temperatures favour the stability of the intermediate-spin state. We therefore infer that ferrous iron adopts the intermediate-spin state throughout the bulk of the lower mantle. Our X-ray data show significant anisotropic compression of lower-mantle perovskite containing intermediate-spin ferrous iron, which correlates strongly with the spin transition. We predict spin-state heterogeneities in the uppermost part of the lower mantle associated with sinking slabs and regions of upwelling. These may affect local properties, including thermal and electrical conductivity, deformation (viscosity) and chemical behaviour, and thereby affect mantle dynamics.
- Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
- Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, USA
- Present address: University of Chicago, CARS, Building 434A, 9700 S. Cass Avenue, Argonne, Illinois 60439, USA (I.K.); Institut Charles Gerhardt UMR CNRS 5253, Equipe PMOF, University Montpellier II, Place Eugene Bataillon, cc1504, 34095 Montpellier cedex 5, France (J.R.)
Correspondence to: C. McCammon1 e-mail: catherine.mccammon@uni-bayreuth.de
MORE ARTICLES LIKE THIS
These links to content published by NPG are automatically generated.
NEWS AND VIEWS
Mineral physics The spin deep withinNature Geoscience News and Views (01 Oct 2008)
Earth Science The mantle deformedNature News and Views (22 Apr 2004)
See all 4 matches for News And ViewsRESEARCH
Supplementary InformationNature Geoscience Letter (01 Oct 2008)
The two main iron-bearing silicate phases in the mantle?ferroperovskite and ferropericlase?are expected to partition iron isotopes differently. Theoretical calculations suggest that the spin state of iron strongly influences the iron isotopic composition of ferropericlase, whereas the iron isotopic composition of ferroperovskite is almost independent of spin state. The two main iron-bearing silicate phases in the mantle?ferroperovskite and ferropericlase?are expected to partition iron isotopes differently. Theoretical calculations suggest that the spin state of iron strongly influences the iron isotopic composition of ferropericlase, whereas the iron isotopic composition of ferroperovskite is almost independent of spin state. Calculated (B3LYP) bond lengths, in picometres (10 Reduced partition function ratiosNature Geoscience Letter (01 Jul 2009)
See all 59 matches for Research
