US EPA

8909312 

Journal Article 

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

Subramani, T; Lilova, K; Abramchuk, M; Leinenweber, KD; Navrotsky, A 

2020 

1 

Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
EISSN: 1091-6490 

117 

46 

28645-28648 

English 

33139534 

10.1073/pnas.2017312117 

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.