Interpretation of geomagnetic data using power spectrum and 3D modeling of Gol-e-Gohar magnetic anomaly

Abstract

In this paper, we have evaluated the magnetic data of Gol-e-Gohar Iron Ore Anomaly No. 8, which is located about 50 km southwest of Sirjan, Kerman Province (Iran). The geological studies showed that the main minerals of the area are magnetite and hematite. Field geomagnetic data were processed after applying diurnal and International Geomagnetic Reference Field (IGRF) corrections. The results revealed two major anomalies including an anomaly in the northern part and another anomaly with northwest-southeast trend in the southeast part. After preliminary studies, the northern anomaly was found to be insignificant and thus the further studies were done only on the southeast anomaly. The aim of the study is to estimate the boundaries (depth to the top, centroid and bottom) of the body in the southeast part based on the analysis of ground magnetic data by using power spectrum. Power spectrum technique was often used to estimate the Curie-point and basement through geophysical data. Based on optimized power spectrum the depth to the top and bottom of the anomaly were estimated as about 36 m and 118 m respectively. To investigate the accuracy of the spectrum's results we have done the 3D modeling in model vision software and then did inversion analysis in Mag 3D environment. We used the results of power spectrum as the input of 3D forward modeling. Inversion results showed that there is a magnetized body which located at azimuth −45° (N45 W) at a depth of 35 to 123 m from surface. The simulation results also showed approximately same result as inverse modeling. Finally, in order to examine to the accuracy of the result we have compared them to boreholes studies which they almost confirmed the above results and the presence of a body containing magnetite.