High-temperature conductivity of magnetite ores in relation to their genesis and mineral composition (by the example of the Goroblagodatskoe skarn-magnetite deposit)

Samples of magnetite ores of different parageneses and mineral compositions from the Goroblagodatskoe skarn-magnetite deposit were studied by physical and mineralogo-petrographic methods. Electrical-resistance curves were obtained for an ore containing 80–90% magnetite for the temperature range 20–800 ºC. Three groups of samples were recognized according to the pattern of temperature curves and electrical resistance: sulfide-free, sulfide-containing (pyrrhotite), and variolitic ores. The parameters of high-temperature conductivity (activation energy E0 and coefficient of electrical resistance logR0) have been determined. A linear relationship between E0 and logR0 (logR0= a – bE0) has been established for magnetite ores of all mineral types. The coefficient a varies from 1.92 to 4.80 depending on the type and mineral composition of magnetite ores. The coefficient b is nearly constant for all studied samples, 6.65. The figurative points of the samples in the E0–logR0 coordinates lie in the field bounded by the straight lines logR0= 4.80 – 6.65E0 and logR0= 1.92 – 6.65E0. The samples of magnetite ores of the skarn and hydrosilicate paragenesis with visible pyrrhotite inclusions and samples of variolitic ores form an individual group in the above field. Within the group, the ores are also subdivided into garnet-magnetite (skarn paragenesis), epidote-chlorite-magnetite (hydrosilicate paragenesis), pyroxene-magnetite, and orthoclase-magnetite (variolitic ores).