Greigite: a true intermediate on the polysulfide pathway to pyrite

摘要: The formation of pyrite (FeS2) from iron monosulfide precursors in anoxic sediments has been suggested to proceed via mackinawite (FeS) and greigite (Fe3S4). Despite decades research, the mechanisms are not sufficiently understood because solid dissolved intermediates oxygen-sensitive poorly crystalline therefore notoriously difficult characterize quantify. In this study, hydrothermal synchrotron-based energy dispersive X-ray diffraction (ED-XRD) methods were used investigate situ real-time transformation polysulfide pathway. rate disappearance specific Bragg peaks during reaction changes morphology phases as observed with high resolution microscopy derive kinetic parameters determine pyrite. results clearly show that is formed an intermediate on pathway kinetics follow a zero-order law indicating solid-state mechanism. crystals under conditions supports conclusion furthermore implies growth by oriented aggregation nanoparticulate greigite, respectively. activation enthalpies entropies determined temperature dependence constants according Eyring equation. Although uncharacteristic mechanism, indicate large increase order transition state, commensurate