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Physics and Chemistry of Minerals

, Volume 41, Issue 7, pp 519–526 | Cite as

Chromium solubility in MgSiO3 ilmenite at high pressure

  • Luca Bindi
  • Ekaterina A. Sirotkina
  • Andrey V. Bobrov
  • Tetsuo Irifune
Original Paper

Abstract

The crystal structure and chemical composition of crystals of (Mg1−x Cr x )(Si1−x Cr x )O3 ilmenite (with x = 0.015, 0.023 and 0.038) synthesized in the model system Mg3Cr2Si3O12–Mg4Si4O12 at 18–19 GPa and 1,600 °C have been investigated. Chromium was found as substitute for both Mg at the octahedral X site and Si at the octahedral Y site, according to the reaction Mg2+ + Si4+ = 2Cr3+. Such substitutions cause a shortening of the <X–O> and a lengthening of the <Y–O> distances with respect to the values typically observed for pure MgSiO3 ilmenite and eskolaite Cr2O3. Although no high Cr contents are considered in the pyrolite model, Cr-bearing ilmenite may be the host for chromium in the Earth’s transition zone. The successful synthesis of ilmenite with high Cr contents and its structural characterization are of key importance because the study of its thermodynamic constants combined with the data on phase relations in the lower-mantle systems can help in the understanding of the seismic velocity and density profiles of the transition zone and the constraining composition and mineralogy of pyrolite in this area of the Earth.

Keywords

Ilmenite Chromium Earth’s transition zone Crystal structure Microprobe analysis Synthesis 

Notes

Acknowledgments

The manuscript took advantage from the revision of two anonymous reviewers. The research was supported by “progetto di Ateneo 2012, University of Firenze” to LB, by C.N.R., Istituto di Geoscienze e Georisorse sezione di Firenze, Italy, the Russian Foundation for Basic Research (Project Nos. 12-05-00426, 12-05-33044, and 14-05-31288) and by the Foundation of the President of the Russian Federation for Leading Scientific Schools (Project No. NSh-5877.2012.5) to ES and AB. ES thanks Geodynamics Research Center, Ehime University, Matsuyama, Japan, for support of her visit in 2013.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Luca Bindi
    • 1
    • 2
  • Ekaterina A. Sirotkina
    • 3
  • Andrey V. Bobrov
    • 3
  • Tetsuo Irifune
    • 4
    • 5
  1. 1.Dipartimento di Scienze della TerraUniversità di FirenzeFlorenceItaly
  2. 2.CNRIstituto di Geoscienze e Georisorse, sezione di FirenzeFlorenceItaly
  3. 3.Department of Petrology, Geological FacultyMoscow State UniversityMoscowRussia
  4. 4.Geodynamics Research CenterEhime UniversityMatsuyamaJapan
  5. 5.Earth-Life Science InstituteTokyo Institute of TechnologyTokyoJapan

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