Greigite (Fe₃S₄) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

Iron sulfide minerals are widespread on Earth and likely in planetary bodies in and beyond our solar system. Using measured enthalpies of formation for three magnetic iron sulfide phases: bulk and nanophase Fe₃S₄ spinel (greigite), and its high-pressuremonoclinic phase, we show that greigite is a st...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-11, Vol.117 (46), p.28645-28648
Main Authors: Subramani, Tamilarasan, Lilova, Kristina, Abramchuk, Mykola, Leinenweber, Kurt D., Navrotsky, Alexandra
Format: Article
Language:English
Subjects:
Ambient temperature
Enthalpy
Iron
Iron sulfides
Magnetic fields
Magnetism
Mercury
Minerals
Phase diagrams
Physical Sciences
Planetary magnetic fields
S phase
Solar system
Spinel
Surface energy
Surface properties
Surface stability
Terrestrial environments
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Summary:Iron sulfide minerals are widespread on Earth and likely in planetary bodies in and beyond our solar system. Using measured enthalpies of formation for three magnetic iron sulfide phases: bulk and nanophase Fe₃S₄ spinel (greigite), and its high-pressuremonoclinic phase, we show that greigite is a stable phase in the Fe–S phase diagram at ambient temperature. The thermodynamic stability and low surface energy of greigite supports the common occurrence of fine-grained Fe₃S₄ in many anoxic terrestrial settings. The high-pressure monoclinic phase, thermodynamically metastable below about 3 GPa, shows a calculated negative P-T slope for its formation from the spinel. The stability of these three phases suggests their potential existence on Mercury and their magnetism may contribute to its present magnetic field.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2017312117