内蒙古陈台屯斑岩型铜矿地质、地球物理特征 及找矿方向

内蒙古陈台屯铜矿区是一个以斑岩型铜矿为主要目标的勘查区,位于大兴安岭中段,成矿时代为中侏罗世。目前在矿区发现了斑岩型铜矿化和脉状铜矿化两种矿化类型。斑岩型铜矿化主要形成于陈台斑岩体顶部与二叠系大石寨组安山质火山岩的内、外接触带上,围岩蚀变作用强烈,并具有明显的分带特征,自下而上、由内到外可分为钾化带、黄铁-绢英岩化带、泥化带和青磐岩化带,斑岩型铜矿化主要集中于黄铁-绢英岩化带中。脉状铜矿主要充填于万宝组沉积地层和大石寨组火山岩的裂隙中,围岩蚀变仅发育黄铁-绢英岩化和弱青磐岩化。通过对矿区开展激电中梯测量和CSAMT电阻率测深并施工钻探验证,发现高极化率异常与斑岩型铜矿体和脉状铜矿体均具有良好的空间对应关系,可以作为下一步铜矿勘查的重要目标;低电阻率异常既可以由斑岩型铜矿化作用所引起,又可以由孔隙度较高的万宝组砂岩所引起,因此首先需要区分异常形成的原因,进而用低电阻率异常指导找矿,但高电阻率异常通常代表了致密的、不含矿的地质体。

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

Abstract: 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.