内蒙古额尔古纳地区八大关铜钼矿床流体包裹体特征与成矿时代

八大关铜钼矿床为内蒙古额尔古纳地区发现较早但研究程度较低的典型斑岩型矿床。为确定其成矿机制、形成时代和构造背景，对主成矿阶段矿石脉石英中的流体包裹体开展了岩相学、显微测温、气相组分的激光拉曼光谱分析，利用LA-ICP-MS锆石U-Pb法和辉钼矿Re-Os法分别测定了成矿石英闪长斑岩体和铜钼矿石的同位素年龄。结果表明：八大关铜钼矿床成矿流体为中高温、中低盐度、中低密度的NaCl-H₂O-CO₂±CH₄流体体系，流体的沸腾作用是矿床形成的重要机制；成矿石英闪长斑岩体的锆石U-Pb同位素年龄的加权平均值为（217.6±2.6）Ma，矿石中辉钼矿的Re-Os模式年龄为（222.4±3.3）Ma，因此八大关矿床的成岩成矿作用发生于晚三叠世。综合本文获得的成岩成矿年龄及前人在区域构造演化方面的研究资料认为，八大关矿床形成于与洋壳俯冲有关的活动大陆边缘构造背景，与蒙古-鄂霍茨克洋向南俯冲所引起的构造-岩浆活动具有密切的成因联系。

Characteristics of Fluid Inclusions and Mineralization Age of Badaguan Cu-Mo Deposit in Erguna Area,Inner Mongolia

The Badaguan porphyry copper-molybdenum deposit was discovered early, but has been low-degree researched. To determine its ore-forming fluid and mineralization mechanism, fluid inclusions in quartz grains from the ore are analyzed, including petrographic characteristics, microthermometry and gas compontents. LA-ICP-MS zircon U-Pb dating of metallogenic quartz diorite porphyry and Re-Os isotopic dating of molybdenite mineral have been carried out. The Badaguan deposit is charactered by the veinlet, network and veinlet-disseminated mineralization and facial zonation of wall-rock alterations, which are similar with those of the porphyry deposits. The ore-forming fluid is of medium- low-density, medium-low-salinity, medium-high-temperature NaCl-H₂O-CO₂±CH₄ fluid system, fluid boiling might be an important mechanism for the formation of mineral deposits. Weighted mean U-Pb age of zircon grains from the metallogenic quartz diorite porphyry is (217.6±2.6)Ma, and Re-Os model age of the molybdenite is (222.4±3.3)Ma, which indicates that the metallogenic intrusion and associated copper-molybdenum mineralization took place in Late Triassic. Moreover, according to the geochemical characteristics and previous data in tectonic environment of the metallogenic porphyry in this area, authors propose that the Badaguan deposit may be resulted from tectonic-magmatism induced by southward subduction of the Mongolia-Okhotsk ocean. These conclusions are very significant for discussion of regional metallogenic regularities and metallogeny in board area among China, Russia and Mongolia.