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Compressibilities along the magnetite–magnesioferrite solid solution

Title data

Melai, Caterina ; Boffa Ballaran, Tiziana ; Uenver-Thiele, L. ; Kurnosov, Alexander ; Chumakov, A. I. ; Bessas, D. ; Frost, Daniel J.:
Compressibilities along the magnetite–magnesioferrite solid solution.
In: Physics and Chemistry of Minerals. Vol. 50 (2023) . - 1.
ISSN 1432-2021

Official URL: Volltext

Project information

Project title:
Project's official title
Project's id
Deep Earth Volatile Cycles
GRK 2156/1

Project financing: Deutsche Forschungsgemeinschaft

Abstract in another language

To calculate the thermodynamic properties of recently discovered high-pressure mixed valence iron oxides in the system Fe–Mg–O, information on the equation of state of precursor inverse spinel phases along the magnetite–magnesioferrite join is needed. The existing equation of state data, particularly for magnesioferrite, are in poor agreement and no data exist for intermediate compositions. In this study, the compressibility of nearly pure magnesioferrite as well as of an intermediate $${{\mathrm{Mg}}_{0.5}}^{\vphantom{2+}}\mathrm{Fe}_{0.5}^{2+}{\mathrm{Fe}}_{2}^{3+}{\mathrm{O}}_{4}^{\vphantom{2+}}$$sample have been investigated for the first time up to approximately 19 and 13 GPa, respectively, using single-crystal X-ray diffraction in a diamond anvil cell. Samples were produced in high-pressure synthesis experiments to promote a high level of cation ordering, with the obtained inversion parameters larger than 0.83. The room pressure unit cell volumes, V0, and bulk moduli, KT0, could be adequately constrained using a second-order Birch–Murnaghan equation of state, which yields V0 = 588.97 (8) Å3 and KT0 = 178.4 (5) GPa for magnesioferrite and V0 = 590.21 (5) Å3 and KT0 = 188.0 (6) GPa for the intermediate composition. As magnetite has KT0 = 180 (1) GPa (Gatta et al. in Phys Chem Min 34:627–635, 2007., this means the variation in KT0 across the magnetite–magnesioferrite solid solution is significantly non-linear, in contrast to several other Fe–Mg spinels. The larger incompressibility of the intermediate composition compared to the two end-members may be a peculiarity of the magnetite–magnesioferrite solid solution caused by an interruption of Fe2+–Fe3+ electron hopping by Mg cations substituting in the octahedral site.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: Magnesioferrite; Fe-rich spinels; Compressibility; Crystal chemistry; Single-crystal X-ray diffraction
Institutions of the University: Research Institutions > Central research institutes > Bavarian Research Institute of Experimental Geochemistry and Geophysics - BGI
Research Institutions
Research Institutions > Central research institutes
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 550 Earth sciences, geology
Date Deposited: 10 Jun 2023 21:00
Last Modified: 23 Aug 2023 12:38