Characteristics of minerals and their associations of transformation processes in pyrite at elevated temperatures: an X-ray diffraction study

Abstract

In order to improve our understanding of the mineral transformation processes in pyrite at elevated temperatures, its heating products at different temperatures between room temperature and 1250°C over a period of 1 h in air were investigated using X-ray diffraction (XRD), and the phases and their diffraction peaks were analysed using X’Pert High Score software. These investigations showed that the temperature ranges of pyrite and its heating products are: pyrite, room temperature to 700°C; 4H-pyrrhotite, 500–1200°C (peak content, 700°C); magnetite, 1000–1200°C (peak content, 1000°C); hematite, the final product, 350–950°C (peak content, 900°C) or ⩾1200°C. Seven mineral paragenetic associations were present during the transformation processes: room temperature to 300°C, pyrite; 350–400°C, pyrite+hematite (trace); 500–700°C, pyrite+4H-pyrrhotite+hematite (trace); 700–950°C, 4H-pyrrhotite+hematite; 1000–1100°C, 4H-pyrrhotite+magnetite; ∼1200°C, hematite+magnetite+pyrrhotite (trace); ⩾1250°C, hematite. Based on these results, we discuss the possible pathways of formation for pyrrhotite, magnetite and hematite.