Geological and Geophysical Characteristics of the Chentaitun Porphyry Copper Deposit in Inner Mongolia and Prospecting Direction

The Chentaitun copper district in Inner Mongolia, dominated by porphyry copper deposits, located in the middle section of the Hinggan Mountain, formed in middle Jurassic time. Two mineralization types have been identified: porphyry copper mineralization and vein-style copper mineralization. Porphyry copper mineralization occurred around the contact zones between the Permian Dashizhai Formation volcanoes and Chentai porphyry intrusion, with intense wall-rock alteration. The alteration associated with porphyry copper mineralization can be divided into four zones from lower to upper or from inside to outside, which are potassic, quartz-sericite-pyrite (QSP), argillic and propylitic zones. Porphyry copper mineralization was predominantly concentrated in the QSP zone. Vein-type copper ores were filled within the fractures of the Wanbao Formation sedimentary strata and Dashizhai Formation volcanic rocks. Central gradient-array induced polarization and CSAMT survey results were verified by diamond drilling. It is concluded that high chargeability anomalies are spatially coincident with both porphyry and vein-type copper orebodies. Therefore, the chargeability high could be key targets for the next stage of exploration. Low resistivity anomalies are not only caused by porphyry copper mineralization, but also generated by the Wanbao Formation sedimentary rocks of high porosity. It is necessary to investigate the reasons before applying the resistivity low to exploration targets. However, the high resistivity anomalies are usually associated with compact and barren geologic bodies.