THE MAGNETIC PHASE TRANSITION AND GEOPHYSICAL CRUSTAL ANOMALIES
磁相变与地壳地球物理异常

In previous work, we suggested a possible additional source of geomagnetic and crustal conductivity anomalies: the so-called second-order magnetic phase transition in the Earth's crust, namely a significant enhancement of the magnetic susceptibility near the Curie (Néel) depth. Some geomagnetic anomalies of unknown origin can be easily explained by this phenomenon. In this paper we summarize the one- and multi-dimensional magnetotelluric signatures due to a thin but very high-permeability body at mid-crustal depth. The magnitude of the anomaly due to a high-permeability layer is comparable to that due to a high-conductivity layer, with opposite sign. Wherever the classical magnetotelluric interpretation produces an unrealistic high-resistivity and extremely thick layer, and the nearby geomagnetic anomalies have a suitable spatial wavelength, the second-order magnetic phase transition might be also considered as possible explanation. Although it has been still questionable whether this phenomenon exists in the Earth's crust, some recent solid state physics laboratory results make it more and more probable that the magnetic phase transition might be a potential source of various geophysical crustal anomalies.