内蒙古宜里钼矿流体包裹体特征及其地质意义

Characteristics of Fluid Inclusions of the Yili Mo Deposit in Inner Mongolia and Their Geological Significance

内蒙古宜里钼矿是大兴安岭北段新近发现的具有大型钼矿前景的中型斑岩型钼矿床。矿区地质特征简单,已发现钼矿体主要分布在F4断层的上盘,辉钼矿呈细(网)脉状产出。赋矿围岩主要为二长花岗岩、正长花岗岩和卧都河组地层。流体包裹体研究表明,宜里钼矿石英脉中的流体包裹体主要呈星散状随机分布或成群分布,其大小集中在3~10μm,形态多样,包裹体类型主要有气液两相、纯液相、纯气相包裹体、含子晶矿物的多相包裹体。包裹体均一温度和盐度呈现出双峰式分布特征,均一温度峰值分别集中在165℃~215℃和265℃~340℃,w(NaCl)%峰值分别集中在为3~7和11~14。成矿流体的密度主要集中在0.613 g/cm3~0.972 g/cm3。综合成矿阶段和成矿特征,成矿流体类型为高温低盐度和中温低盐度的中等密度的成矿流体。根据成矿压力估算,矿床形成古深度约为1.24~1.52km。包裹体激光拉曼光谱分析表明包裹体中气相和液相成分均以H2O、CO2为主,并发现有含黄铜矿子晶包裹体,代表了成矿阶段的流体特征。

The Yili Mo deposit located in the northern Daxing'anling Mountains is a newly found medium-scale Mo deposit. It has simple geology in the mining area,where ore bodies are discovered mainly in the hanging wall of the F4 fault. Host rocks are monzonitic granite,syenogranite and Woduhe group rocks. The main mineralized type is veinlet-disseminated. Fluid inclusions in quartz veins suggest that these inclusions are distributed in groups or scattered stars randomly with long axes of 3 ~ 10μm. The types of fluid inclusions include two-phase,pure liquid,pure gas and multi-phase inclusions with daughter minerals. Homogenization temperature and salinity show a bimodal distribution that homogenization temperature peaks are concentrated in 165℃ ~ 215℃ and 265℃ ~ 340℃,and w( NaCl) % peaks in 3 ~ 7 and 11 ~ 14,respectively. The density of ore-forming fluids ranges 0. 613 g / cm3~ 0. 972 g / cm3. A comprehensive analysis indicates that ore-forming fluid types include high-temperature with low-salinity and medium-temperature with low salinity,and all have a medium density. Laser Raman spectroscopy studies show that the inclusions in gas and liquid ingredients are mainly H2O and CO2. And a chalcopyrite crystal was found in inclusions indicative of a characteristic of ore-forming stage fluid.