Home – Home – Jornals – Russian Geology and Geophysics 2015 number 11

The magnetic viscosity of geologic media exerts a significant, often high and sometimes predominant influence on the pulse induction characteristics measured in the laboratory and in the field. Compared with the frequency methods, measurement of pulse magnetization parameters has advantage, namely, magnetic viscosity is observed in the absence of the primary field, and the transitive pulse parameter is measured over a wide time range. This reduces the error of measurement of parameters characterizing magnetic viscosity. In contrast to the transitive parameter, its derivative, i.e., a pulse parameter, is not influenced by a constant (slowly decreasing) component of the total residual magnetization. This eliminates the problem of the uncertainty on the separation of low-viscosity component from the total magnetization. The temporal decrease in the pulse parameters of magnetization is described by the power function a · t-b , where a is the initial value (varies over a wide range) and b is the exponent close to unity. As shown by the measurements made with the use of induction coil systems, the parameter a shows a strong linear correlation with the frequency-dependent magnetic susceptibility Δ k , which is commonly used to evaluate the content of superparamagnetic particles. This suggests that the pulse induction systems can be used for an express study of a large number of samples in order to identify SP-particles and estimate their contents. Although the exponent b differs negligibly from unity, this difference is much higher than the error of determination of this parameter from the experimental data. Mathematical modeling of the pulse parameters of magnetization has shown that both are influenced by the distribution of the particle volume, which makes prerequisites for solving the inverse problem, i.e., finding the distribution that provides the best explanation of the experimental pulse parameters.