عنوان مقاله [English]
Increasing demands of raw materials and energy resources has led to a fast growth in the geophysical studies. Due to the properties of minerals and geological conditions, there are various geophysical methods. Among these methods, magnetic method is capable of exploring the magnetic mineralization of rocks with relatively high or low magnetic properties. In this method, the magnetic field variations of the ground are measured. Sonajeel is located 17 kilometers from Harris, East Azarbaijan Province. The main stone units in this area are from the old to the new: volcanic and volcanoclastic rocks, Sonajeel porphyry stock, Incheh granitoid stock, and Okuzdaghi volcanic rocks. In this study, the magnetic method is used as an indirect method for identification of copper ore deposits. Based on the magnetic method, information can be obtained about the gradient, depth, shape, and extension of the source of anomalies. There are several examples for using this method (especially the airborne magnetic method) to explore the copper deposits. Including the copper project in the Cadia region of Australia, as well as the use of magnetism to explore the mineralization of copper and gold in the polymetal exploration area of Bashmaq Hashtrood. For the aim of identification of copper mineralization in the study area, the magnetic data along 19 survey lines were carried out. The length of each line was considered to be1000 meters and magnetic measurements were made at magnetic stations having distance intervals of 20 meters. The distance between the successive survey lines was 50 meters, except the distance between survey lines 19 and 18 that were located 30 meters from each other. The total survey area was about 1 km2. After applying diurnal correction on the magnetic data, the processing of the data was made by applying various filters such as reduction to the pole (RTP) to remove the effect of the inclination angle and to locate the subsurface position of the anomaly that is assumed to be symmetrically placed on the creator mass, upward continuation filter to study the process of mineralization in depth, and also, vertical derivatives and analytical signal processing methods were used to estimate the anomalous boundaries. Three-dimensional (3D) modeling of the magnetic data was also carried out using the Mag3d software. The results indicated that the mineralization process was extended in the north and north-east to the south-east of the study area. Upward continuation filtering was applied to the data at altitudes of 20, 40, 80 meters. The maps resulting from this filtering represented the root of the subsurface anomaly in the southeastern of the region. As a result of comparison of the various magnetic images with the 3D model, obtained from modeling the magnetic data using the Mag3d software, we found out that the copper mineralization in the study area is scattered but covers a large range of the area. Moreover, according to the results of 3D modeling of the data, the magnetite susceptibility in north and northeast of the study area is more than that in south and southeast of the area. The contrast of the magnetic susceptibility in north of the study area from the depth of 100 m to 270 was high, however, in the east and southeastern parts of the study area, from the depth of more than 100 meters, there was a high magnitude of magnetic susceptibility. Hence, it can be concluded that in the northern parts of the study area, potassic alteration was closer to the ground surface. It should be mentioned that the potassic alteration is a good place for copper and magnetite mineralization as the copper and magnetite mineralization is located in the center or middle of the potassic alteration. By comparing and interpreting the magnetic results and assessing these results with the geological data or information from the study area, the probability of occurrence of the magnetite mineral and, consequently, the copper mineralization or deposits in the Sonajeel area is highly indicated.