祁漫塔格地区肯德可克铁钴多金属矿围岩时代及其意义

东昆仑祁漫塔格地区肯德可克铁钴多金属矿成因类型存在较大争议,对该矿形成构造环境和围岩条件认识的不一致性是重要因素之一,尤其是赋矿围岩时代。本文依据采获的类和腕足类化石,将肯德可克铁钴多金属矿南部围岩重新厘定为下二叠统。利用LA-ICP-MS锆石U-Pb测年技术,获得肯德可克铁钴多金属矿北侧英安质熔结凝灰岩形成年龄为227.1±1.2 Ma,相当于晚三叠世早期,为其划归上三叠统鄂拉山组提供了直接证据。通过野外调研和岩相学研究,认为肯德可克铁钴多金属矿北侧"矽卡岩"属于火山作用形成的中-高温矿化蚀变带,并非典型的矽卡岩。综合分析认为,肯德可克铁钴多金属矿的形成时代不早于早二叠世,主成矿期为晚三叠世的可能性较大,成因类型可能属于火山-热液型多金属矿床,上三叠统鄂拉山组下部中-高温矿化蚀变带可作为寻找这类矿床的重要标志之一。

The age of country rocks of the Kendekeke Fe-Co polymetalic deposit in Qimantag area and its significance

The inconsistent opinions concerning the tectonic setting, the surrounding rock environment and, especially, the age of the wall rocks, have caused much controversy about the metallogenic type of the Kendekeke Fe-Co polymetallic deposit in Qimantag area, East Kunlun Mountains. According to Fusulinida and brachiopod fossils, the authors re-assigned the southern part of the country rock to Lower Permian. LA-ICP-MS zircon U-Pb dating of the dacitic ignimbrite from the north of the deposit yielded the age of 227.1±1.2 Ma, which provides direct evidence for the assigning of this strata to Upper Triassic Elashan Formation. Field investigation and petrographic study have led the authors to believe that the "skarn" on the northern side of the Kendekeke Fe-Co polymetallic deposit should belong to the volcanic middle-high temperature mineralization-alteration zone rather than being a typical skarn. Based on a comprehensive analysis, the authors hold that the mineralization age of the Kendekeke Fe-Co polymetallic deposit should not be earlier than Early Permian, and the main mineralization likely took place in Late Triassic. The metallogenic type may belong to volcanic-hydrothermal polymetallic type. The middle-high temperature mineralization-alteration zone in the lower part of the Upper Triassic Elashan Formation should be one of the important prospecting criteria in search for this kind of Fe-Co polymetallic deposits in this region.