Fluid Inclusion And Ore Genesis Characteristics Of The Huojihe Molybdenum Deposit In Heilongjiang

The Huojihe molybdenum deposit is in the north of Lesser Xingan RangeZhangguangcai Range metallogenic belt where the tectonic and magmatic activities are frequent,resulting in a large area of the medium-acidic magmatic rocks.It provides abundant fluids,materials and heat source in the area.Finally,it forms many porphyry deposits,skarn deposits,and hydrothermal quartz vein deposits.Previous studies on fluid inclusion are not systematic and the results are deviated.Based on the research of the previous studies and the observation of the outcrops in the field,this paper discusses the origin of metallogenic fluid and the source of metallogenic material through the study of the geological characteristics,the fluid inclusion and the isotope geochemistry of the ore deposit.According to the studies,the genesis and metallogenic model of the ore deposit can be concluded.The hydrothermal veins of the Huojihe molybdenum deposit were divided into A vein,B vein,D vein and calcite vein.Early stage A veins are the gray quartz-and sulfide-free veins,and the boundary of the veins is relatively straight,characterized by rare sulfide.The main stage B veins are the sulfide-bearing and granular quartz-dominated veins.The boundary of the vein body is straight,and the vein body is symmetrical.The sulfide is often parallel to the continuous distribution of the veins.The metal sulfide is dominated by the molybdenum ore.It is not readily recognizable alteration.Late stage D vein is quartz-sulfide veins.The veins are more regular and continuous,and the veins are asymmetrical.The metal sulfide mainly consists of pyrite.Calcite,less quartz and sulfide are the mineral assemblages of the calcite vein.The results of the microthermometry shows that this is a high temperature,high salinity,and low density fluid.A vein type of inclusions is rich in the gas-liquid water two-phase inclusions and can rarely daughter-mineral three-phase inclusions.The homogenization temperature is ranged from 292°C to 442°C,and the salinity is 6.74 ~ 12.85 wt%NaCl and 38.20 ~ 49.92 wt%NaCl.B vein type of inclusions is rich in the gas-liquid water two-phase inclusions and can rarely daughter-mineral three-phase inclusions and gas water inclusions.The homogenization temperature is 243°C ~ 389°C,and the salinity is 4.65 ~ 10.61 wt%NaCl and 35.63 ~ 42.79 wt%NaCl.D vein type of inclusions is rich of in the gas-liquid water two-phase inclusions.The homogenization temperature is 202 ~ 335°C,and the salinity is 4.1 ~ 7.86 wt%NaCl.The calcite vein type of inclusions is rich in the gas-liquid water two-phase inclusions and can rarely liquid water inclusions.From the eraly stage to the late stage,the homogenization temperature,the salinity,the pressure and the depth of the metallogenetic fluid have the tendency of decreasing while the density is slightly increasing.The H-O isotope indicates that the fluid is mainly from the magmatic water,while the late stage ore-forming fluid is dominated by the meteoric water.S and Pb isotopes indicate that the metallogenic materials are derived from a crust-mantle mixed source,and it is closely related to the granodiorite.The Huojihe molybdenum deposit is a typical Porphyry molybdenum deposit by the ore characteristics,minerals coexisting relationship and ore textures.