The Longtoushan polymetallic sulfide deposit is located on the east slope of the middle-south Da Hing-gan Mountains and the north side of the Xar Moron River fault along the Hercynian geosyncline fold belt. Field geological survey shows that the ore deposit has two mineralization types, namely layered mineralization and cylinder mineralization. Attitudes, alterations and minerals of the two mineralizeation types show typical characteristics of submarine hydrothermal sedimentary deposition. A systematic study of fluid inclusion petrography and microthermometry was carried out for fluid inclusions in syndepositional barite from the ore deposit. The inclusions in the barite suggest rapid sedimentary characteristics during the hydrothermal sedimentary deposition. Except for secondary fluid inclusions, gas-pure and gas-rich inclusions related to the mineralization are very rare, with the majority being liquid-rich inclusions. Microtherrnometric analysis shows that the liquid-rich inclusions have homogenization temperature 101.4~279.9℃,freezing temperature-5.5 ~ - 0.3℃,salinity 0.5%～8.5%, and fluid density 0.75～0.97 g/cm3. Reflective features such as temperature, salinity and density of the ore fluids are consistent with features of the inclusions developed in submarine hydrothermal sedimentary sul-fides ore deposits. The results provide positive evidence for the viewpoint that the Longtoushan polymetallic sul-fide ore deposit is a marine hydrothermal sedimentation deposit.%龙头山多金属硫化物矿床位于内蒙古大兴安岭中南段东坡,海西期地槽褶皱带西拉木伦河深大断裂北侧.野外地质研究发现,该矿床主要发育层状和筒柱状两类矿化,两类矿化的产状、蚀变、矿物特征等显示出典型的海底热水沉积成矿作用特征.对与该矿床金属硫化物同生沉积的重晶石进行流体包裹体岩相学研究发现,重晶石中的包裹体反映了热水沉积成矿期快速沉淀的特征,除次生包裹体外,与成矿作用有关的流体包裹体中纯气相和富气相包裹体很少,主要是富液相包裹体；对重晶石中富液相包裹体的显微测温研究发现,其均一温度为101.4～279.9℃,冰点温度为-5.5～-0.3℃,盐度为0.5％～8.5％,所代表的成矿流体密度为0.75～0.97 g/cm3,反映的成矿流体温度、盐度、密度等特征符合典型海底热水沉积硫化物矿床的包裹体特征.
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