云南马厂箐铜钼矿床碱性杂岩体期次划分及LA-ICP-MS锆石U-Pb定年

云南省马厂箐铜矿床位于“三江”成矿带中南段,是大陆碰撞环境下与喜马拉雅期碱性斑岩有关的矿床,矿区大面积出露的碱性杂岩体是一复式岩体,与成矿作用关系密切。文章通过大量野外调查和室内工作,对其侵入时间、侵入期次和各期次岩性组合特征进行了研究,认为马厂箐岩体共经历了3期演化:Ⅰ期正长斑岩、石英正长斑岩→Ⅱ期斑状花岗岩、早期煌斑岩→Ⅲ期花岗斑岩、晚期煌斑岩。其中Ⅰ期不成矿,Ⅱ期与Ⅲ期岩浆活动与成矿关系密切。通过LA-ICP-MS锆石U-Pb同位素年龄测试,确定其形成时代在32.4～38.5 Ma之间,其活动时间与印度—亚洲碰撞带岩浆活动主要成矿时间和青藏高原晚碰撞阶段成矿高峰期时间一致。

Classification of intrusion stages of the alkalic complex and U-Pb dating of LA-ICP-MS zircon of the Machangqing Cu-Mo deposit, Yunnan Province

The Machangqing Cu-Mo deposit located in the central-southern part of Sanjiang metallogenic belt in Yunnan Province, is an alkaline porphyry type deposit of Himalayan period in the continental collision environment. The alkalic complex which outcrops widely in Machangqing deposit area is a duplex pluton, and is closely related to the copper-molybdenum mineralization. Based on the large amount of field investigation data and indoor research information, the intrusion age and stages of intrusion of the alkaline complex, and the lithological association of each period alkaline rockmass were studied, and the evolution of the Machangqing alkalic complex was classified into three stages, i.e., the first stage of syenite and quartz syenite porphyry, the second stage of porphyritic granite and early lamprophyre dike, and the third stage of granite porphyry and late lamprophyre dike. Among them, there is no mineralization associated with the first stage of intrusion, and extensive mineralization with the second and third stages of intrusion. Based on the U-Pb isotope measurement of the zircon mineral by LA-ICP-MS, it is interpreted that the formation age of Machangqing alkalic complex ranges from 32.4 Ma to 38.5 Ma. The intrusion age is consistent with the period of the magmatic metallogenesis within the India-Asia plate collision zone and the period of the main mineralization in the late Qingzang plate collision.