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

ABSTRACT: 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-pressure monoclinic 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.

SUBMITTER: Subramani T

PROVIDER: S-EPMC7682356 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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

Subramani Tamilarasan T Lilova Kristina K Abramchuk Mykola M Leinenweber Kurt D KD Navrotsky Alexandra A

Proceedings of the National Academy of Sciences of the United States of America 20201102 46

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-pressure monoclinic 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 Fe<sub ...[more]

PMID: 33139534

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