Metastable structural-magnetic transformations in sulphides in course of oxidation

The modelling of the oxidation process of pyrite (FeS2) has been performed to explain the complex phase creations in the natural massive sulphide deposits of hydrothermal origin. We studied the multistage structural magnetic transformations of pyrite on the air within the temperature interval of 20-700 C deg by means of Moessbauer spectroscopy, thermomagnetic analysis and x-ray diffraction. The emergency of hexagonal and monoclinic nonstoichiometric pyrrhotites with varied degree of vacancy ordering and disordering have been observed. The Curie points of those metastable phases change within the limits of 120-240 C deg for hexagonal and within 320-460 C deg for monoclinic pyrrhotites. (author) 6 refs.; 3 figs.; 1 tab