| The Qianjiadian uranium deposit is located in the northeast of Kailu Sag,Songliao Basin.The lithology of the basement of the basin is mainly late Paleozoic shallow metamorphic rock,Jurassic acidic volcanic rock and granite.The cover is composed of qingshankou formation,Yaojia Formation and Nenjiang Formation of the Upper Cretaceous.Yaojia Formation is the main ore-bearing horizon,and the lithology is mainly fine grained gray-white feldspar lithic sandstone.In this paper,the qianjiadian uranium deposit is taken as the research object,and the characteristics of diagenetic and ore-forming fluids are identified through systematic fluid inclusion studies,and the relationship between oil and gas migration and uranium mineralization is discussed,so as to provide necessary basis for profoundly revealing the genesis of this type of deposit.Through mineral bearing sandstone thin section identification,cathodoluminescence,dyeing and scanning electron microscopy(sem)experiments,containing ore Yaojia sandstone diagenesis is divided into syngenetic stage,early diagenetic stage,middle diagenetic stage,late diagenetic stage and epigenetic stage,build the diagenetic evolution sequence.The fluid inclusion in the quartz enlarging edge can reflect the characteristics of diagenetic fluid.The results of petrography and microthermometing show that the fluid inclusions in the quartz enlarging edge are mainly gas-liquid two-phase inclusions,the homogenization temperature varies from 60.5 ? to 115?,and the salinity varies from 4.1 to 8.1 wt.% Na Cl eqv.,indicating that the diagenetic fluid is a low temperature and low salinity fluid.Based on the electron probe experiment and a large number of previous experimental results,uranium minerals were found in both siliceous cements and carbonate cements,indicating that they are products of mineralization period,so the fluid inclusion in them can reflect the characteristics of ore-forming fluids.Petrography and microthermometry results of fluid inclusions show that the fluid inclusions in siliceous cements and carbonate cements are mainly gas-liquid two-phase inclusions,homogenization temperature varies from 105 ? to161.4?,and fluid salinity varies from 1.7 % to 6.1 wt.% Na Cl eqv.,indicating that the ore-forming fluid is low temperature and low salinity fluid.Compared with the diagenetic fluid,the ore-forming fluid has a higher temperature(40?±)and a slightly lower salinity(2 wt.% Na Cl eqv.±).They are two different fluids.Organic inclusions are developed in ore-bearing sandstones,mainly occurring in quartz enlarging edge,particle dissolution pore,particle fissure and cement,and homogenization temperature is between 60 ? and 130?.By analyzing the relationship between the time of oil and gas migration and uranium mineralization and the relationship between the occurrence of organic inclusions and uranium minerals,it is concluded that the time of oil and gas primary migration is earlier than that of uranium mineralization.The comparative analysis of the spatial relationship between temperature and salinity of ore-forming fluid and uranium mineralization intensity shows that the change of temperature and salinity of fluid inclusions is not the direct factor affecting uranium mineral precipitation.However,the petrographic characteristics of ore-bearing sandstones and the occurrence state of uranium minerals indicate that the superimposition of hydrothermal fluid,the adsorption of clay minerals and the reduction of pyrite may be the main factors causing uranium mineral precipitation. |
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