Thermal equation of state of Fe₃O₄ magnetite up to 16 GPa and 1100 K

Titelangaben

Siersch, Nicki C. ; Criniti, Giacomo ; Kurnosov, Alexander ; Glazyrin, Konstantin ; Antonangeli, Daniele:
Thermal equation of state of Fe₃O₄ magnetite up to 16 GPa and 1100 K.
In: American Mineralogist. Bd. 108 (2023) Heft 7 . - S. 1322-1329.
ISSN 1945-3027
DOI: https://doi.org/10.2138/am-2022-8571

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Abstract

Fe3O4 magnetite is an important mineral commonly found in various geological settings, including the planet Mars, whose thermoelastic properties at high pressure and temperature are still poorly constrained. We performed X-ray diffraction measurements on natural magnetite using resistive-heated diamond-anvil cells up to 16 GPa and 1100 K. We fitted a thermal equation of state (EoS) to the collected data resulting in K0 = 182(1) GPa, K0′ = 4, θD = 660 K, γ = 1.8(1), and q = 2.7. Moreover, it was possible to explore the structural evolution of magnetite in detail using single-crystal measurements. Over the studied pressure and temperature range, we found no evidence of a transformation from an inverse to a normal spinel structure. The EoS parameters obtained in this study will be implemented into currently available databases for self-consistent thermodynamic modeling. In particular, our results are used to model and compare the sound wave velocities of a magnetite-bearing and magnetite-free martian upper mantle assemblage. We observe that the incorporation of magnetite reduces the sound wave velocities; however, the magnitude of the effect is below the current seismic detection limit of the InSight mission on Mars at the low abundance of magnetite expected in the martian mantle.