High-temperature electrical conductivity of chromite ores from the Alapaevsky hyperbasite massif, Middle Urals, as a function of their composition and metamorphism

   Research subject. Chromite ores and massive chromitites with alumina (low chromium) chrome spinelide (the Podennoye deposit deposit) and chromite ores with high-chromium chrome spinelide (Kurmanovskoye deposit) of the Alapaevsky hyperbasite massif.   Materials and methods. Samples of chromite ores and massive chromitites collected during field research were studied in transparent sections using chemical analysis and electrical methods (electrical conductivity, dielectric losses).   Results. The temperature dependences of electrical resistance and dielectric losses in the temperature range of 20‒800°C were obtained. The electrical parameters lgRₒ and Eₒ were determined, and the inverse linear relationship bet-ween them was revealed. The electrical parameters for the three groups of samples were found to differ depending on the degree of metamorphic changes. It was established that an increase in metamorphism leads to an increase in lgRₒ and a decrease in Eₒ. For the studied samples of chromite ore from the Podennoye deposit, Eₒ and lgRₒ vary from 0.61 to 0.96 and from 2.5 to –0.41, respectively. In the Kurmanovskoye field, these parameters vary from 0.81 to 1.35 and from 0.95 to –2.8, respectively. For the studied samples of chromitites from the Podennoye deposit, Eₒ varies from 0.21 to 0.41, while lgRₒ varies from –0.08 to 1.67. In this case, the coefficients a and b are different for each group of samples. For some samples, the chemical composition was determined, and for six samples (two samples from each group), the content of ferrous and trivalent iron oxides in the original sample and a duplicate sample after calcination at temperature of up to 800 °C was determined. Relative change in the ratio of ferrous and trivalent iron oxides in the initial sample (FeO/Fe2O3)* and a duplicate sample (FeO/Fe2O3)** H = [(FeO/Fe2O3)*/(FeO/Fe2O3)**] was compared with the position of the maximum of dielectric losses on the temperature scale. In the coordinates H–T, °C, the studied samples, depending on the metamorphic changes, occupy a certain place.   Conclusions. The study indicates the potential of the obtained information to be used as petrogenetic indicators of chromite deposits with a simultaneous assessment of the degree of metamorphic changes.