Vestnik MGTU (Apr 2020)
Residual magnetization of various genetic rocks and ores of the Kola region under the influence of mechanical oscillations
Abstract
The paper considers magnetoelastic phenomena in rock samples. Research is of interest for solving problems of nonlinear geophysics, as well as of some issues of materials science. Magnetite-bearing rocks and ores have been sampled in different geological structures of the Kola region in order to study their magnetoelastic properties. All samples have been subject to elastic mechanical oscillations in laboratory conditions. The experiment has been conducted under changing impact parameters of acoustic waves. The effect of signal amplitude on magnetic properties of the samples has been first studied using magnetite-bearing amphibolites from the Serpovidny Ridge structure. According to results of the experiment, it is considered reasonable to use a pulse signal with higher amplitude in the future. An effect of a signal direction regarding a vector of residual magnetization has been studied, using rocks with different ferromagnetic contents. Values of natural residual magnetization of the studied samples vary from 100 А/m to 0.5 А/m. The study has indicated some relation between a spatial behavior of a vector and a direction of the acoustic impact in rocks with high magnetite content. In particular, the spatial location of the vector changes considerably, when the angle between the direction of the acoustic wave front and the magnetization vector of samples is 100 degrees and more. No statistically significant relations or patterns have been identified for low-magnetic samples. At the final stage, the effect of duration of elastic mechanical oscillations impact on magnetic properties of rocks has been studied. Results of the research also indicate an interrelation between an impact of this acoustic effect and an amount of the magnetic matter in the rock. Thus, a significant response of the samples' magnetic state is registered during the acoustic impact on rocks with high ferromagnetic content. In general, it has been concluded that studying electromagnetic effects on high-magnetic samples is more promising compared to rock samples with lower ferromagnetic content.
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