MODIFIED MAGNETITE AND MAGHEMITE IN MAGNETITE QUARTZITES OF THE KREMENCHUK IRON ORE REGION

A study of magnetite ores of the Kremenchuk iron ore region with different degrees of maghemitization, concentrates and weakly magnetic fractions from them was carried out using the X-ray diffraction (XRD) method, thermomagnetic analysis (TMA) and ferromagnetic resonance (FMR). It was shown that the complex use of magnetic methods allows detecting ferromagnetic phases and changes in the magnetic structure of magnetite that are weakly manifested in diffractograms. By comparing TMA and FMR data in magnetite quartzites, at least 2 types of cation-deficient (z-Mag1 and z-Mag2) magnetite of lower and higher oxidation states with Curie points (ТС) near 540 and 500 °C, respectively, were established. The magnetic phase with ТС > 580 °C is attributed to thin intergrowths of near-stoichiometric magnetite and maghemite, rather than maghemitized magnetite. Maghemitized magnetite was found in various types of ores and industrial concentrates after the first dry magnetic separation, which indicates its significant (up to ~10%) distribution in the Kremenchuk iron ore region. It is assumed that z-Mag1 and z-Mag2 may be from a finely dispersed generation dispersed in quartz at the diagenetic stage, and the others from the early metamorphic generation stage of ore evolution. Obtained results confirm the assumption that magnetite and maghemite are only the extreme members of the continuous series of magnetitomaghemites — kenomagnetites. The results of the work can be used in assessing the technological characteristics of magnetite quartzites when preparing them for enrichment and in assessing the parameters of iron ore pellets.