The Terminal of Mineral System Exploration in Thick Coverage Area by Gravity and Magnetic Data—A Case Study on the Nihe Iron Deposit

gravity data aiming at evaluating the terminal of mineral system. Nihe iron deposit, situated in the center of Luzong ore cluster area, is the case to our study. Different tectonic environments, source material, and preservation background illustrate distinct properties in the geophysical observation results. Geophysical detection applies the characteristic differences of velocity density, magnetic susceptibility, polarizability, electrical resistance (conductivity), and wave impedance to detect the deep geological union. The multi-scale mineral system detection need to analyze the source, path, accumulation, and preservation in order to delineate the deep processes in multiple scales and targets prospecting. Ore-forming material induced by the regional geodynamic movement underwent transportation, enrichment, and storage conditions changes forming the ore deposit (Lü et al., 2015, 2021; Hagemann et al., 2016). In this paper, taking Nihe iron deposit in Luzong ore cluster area as an example, the aeromagnetic and gravity methods of prospecting give a high resolution delineation of the subsurface structures. The fine processed potential data, reduced to pole (RTP) total aeromagnetic intensity map and the Bouguer anomaly map, was used to analyze the terminal of mineral system. As a result, we get the corresponding depth and the horizontal distribution characteristics of Nihe iron deposit. Our results show gravity and magnetic detection method has an important application effects in the terminal exploration of the mineral system. The research of the terminal in mineral system focuses on three-dimensional (3D) structure of the ore-forming rock mass and the prediction of the metallogenic target area. Airborne gravity and magnetic detection has attracted much attention because of its advantages of low cost, easy operation and high proficiency to detect the terminal of mineral system in thick coverage areas. Felsic– ultrafelsic rocks show high magnetic and high gravity anomalies, so the magnetism and density differences between different ore-bearing rock can be used to delineate the boundary of the rock mass and the target area for metallogenesis. In the process of metallic enrichment, fractures are the migration path and (or) enrichment sites of ore-forming fluids. Therefore, targeting the ore-body enrichment channels and the spatial distribution of oreforming rock bodies has become an important goal of ore deposits exploration. Modeling the results of gravity and magnetic inversion, the 3D visualization can intuitively display the distribution, occurrence, and scope of mafic ore bodies and provide support for estimating the endowment of resources (Howe et al., 2014; McCuaig and Hronsky, 2014; Luo et al., 2018; Zhou et al., 2021). Nihe iron deposit was discovered in the middle part of the Middle and Lower Yangtze metallogenic belt, which was mainly divided into three mineral serials: the magnetite in the southwest, the pyrite in the northeast and the transitional anhydrite section in the middle. According to previous research, the proved reserves of iron ore resources were 184 million tons, pyrite resources were 140 million tons, and anhydrite resources were 13.63 million tons. The former two reaches the large scale deposit and the latter is a medium-sized deposit. Nihe Iron deposit is a major breakthrough in deep prospecting in the Middle and Lower Yangtze metallogenic belt. The predecessors have conducted detailed studies on the geological characteristics, geochemical characteristics, wall rock alteration and sulfur isotopes of the deposit, and each proposed a diagenetic and mineralization model (Zhao et al., 2011; Zhou et al., 2011; Yan et al., 2014, 2019). The technical combination of Nihe iron deposit positioning prediction methods is discussed on the basis of fully understanding the geological ore-controlling laws of the mining area and clarifying the prospecting direction. Besides, the study must combine the perspective of The Terminal of Mineral System Exploration in Thick Coverage Area by Gravity and Magnetic Data―A Case Study on the Nihe Iron Deposit