Analysis of dielectric losses in chromespinelide samples from the ophiolite complexes of the Urals

Relevance is determined by the need to search for scientifically based criteria for the identification of chromite mineralization. The purpose of this work is to study the features of dielectric losses and their temperature dependence of ore-forming chromespinelides in relation to the chemical composition and phase transformations in their structure. Research methodology. To study the dielectric properties of chromespinelides, samples were prepared in the form of a cube with an edge of 0.02 m (two cube samples were prepared from each sample). Measurements were performed in an open system at atmospheric pressure. Dielectric losses were measured with a two-electrode setup every 10 degrees in the temperature range 20–900 °C. Heating rate is 4 deg/min. The temperature in the system was determined with a platinum-piatinum-rhodium thermoeiectric coupie at 0.01 m from the sampie. As a measuring device for determining the tangent of the angie of dielectric losses (tg δ) at alternating voitage, the “Digitai L, C, R Meter” E7-8 was used. The operating frequency of the device is 1 kHz. In the initial sample and the duplicate sampie after its roasting to 900 °C, the content of oxides of ferrous and ferric iron was determined. The reiative change in the ratios of oxide and ferrous iron in the initial sample and in the dupiicate sample after roasting was compared with the position of the maximum dielectric losses on the temperature scale. Results. Samples of chromite ore from various deposits and ore occurrences of the Urals were studied by physical, physicochemical, mineralogical and petrographic methods. The temperature dependences of dielectric losses of 21 samples of chromite ore, consisting of 80–90% of chromespinelides, were obtained. All curves clearly show the maximum dieiectric iosses. This indicates that the losses are of a relaxation nature. The position of the maximum on the temperature scaie is different for the studied chromespinelides and is mainly associated with a change in the ratio H. H value is the relative change in the ratio of oxide and ferrous iron FeO/Fe2 O3 in a chromespinelide sample during its heating to 900 °C. The position of the maximum dielectric losses for the studied samples varies from 450 °C (sampie 1 – massive chromitite from the Podenny mine III deposit – Alapaevsi<y massif) to 842 °C (sample 21 – massive chromite ore from the Tsentrainy deposit – Ray-lz massif). In this case, H vaiue varies from 1.61 to 11.14, respectively. A relationship was revealed between the position of the maximum dieiectric losses on the temperature scale of the studied samples of chromite ore and the parameter H. Conclusions. The above results in combination with other physicochemical parameters can be used as an indicator of a rapid assessment of the type of mineralization.