Conversions of Magnetic Anomaly and 3-D Inversion at Low Magnetic Latitudes

Abstract

At low magnetic latitudes, the magnetization direction is almost horizontal, amplification effect of pole reduction factor causes band-shape fake anomaly along the direction of the magnetic declination. Experts have been solving the problem pole reduction at low magnetic latitudes (RTP-L). However, no greatly effective method has been found. The magnetic anomaly with a reduction procedure at low magnetic latitudes misleads the judgment of experts if the method is not well used. For making a reliable magnetic anomaly interpretation result at low magnetic latitudes, it is proposed that a pole reduction procedure can be approximately simulated by the total field multiplied by -1 in this paper. In addition, a comprehensive magnetic anomaly conversions and inversion method is assembled and restricted at low magnetic latitudes including non-linear filter, analytic signal and 3-D inversion to avoid the distortion of magnetic anomaly during reduction to pole (RTP). This method takes into account the magnetic anomaly characteristics at low magnetic latitudes. The application of this method can prevent the uncertain factor of RTP-L, give the boundary of magnetite, and provide shapes and size of magnetite effectively without involving the directions of magnetization. It made good effect in Pampa de Pongo Fe deposit in Peru which is located near the magnetic equator (inclination=5.5°). Therefore, a simple method to simulate RTP-L, combined with non-linear filter, analytic signal, 3-D inversion, can enhance the reliability and accuracy of magnetic anomalies interpretation at low magnetic latitudes.