| Xiangshan uranium ore field is an important volcanic-type uranium ore field in China.There are more than 20 uranium deposits in the area,which are mainly divided into three types:volcanic lava subtype,subvolcanic rock subtype and cryptoexplosive breccia type.The former two types are dominant,while cryptoexplosive breccia has only one Baquan deposit.The similarities and differences of fluid inclusion characteristics between volcanic lava subtype and subvolcanic subtype uranium deposits may provide relevant information of mineralization,and provide reference for exploration of mineralization process,genetic analysis of ore deposits and regional prospecting.Zoujiashan deposit,Yunji deposit,Julongan deposit belong to volcanic lava subtype.Shannan deposit and Shazhou deposit belong to subvolcanic subtype.Both of them are selected as research objects.On the basis of existing work,through field geological survey,thin section microscopy identification,scanning electron microscopy,fluid inclusion temperature measurement,the characteristics of fluid inclusions are compared,and Xiangshan metallogenic model is discussed.The main achievements are as follows:?1?The homogenization temperature of fluid inclusions in Xiangshan uranium ore field varies from 160-400 C.The peak distributions are:Zoujiashan 122-162?,242-298?,cloud 160-187?,227-287?,Julongan 220-260?,Shannan 220.5-240?,261.7-298.2?,Shazhou 201-240?,280-298?,325.6-340?.The values of the two subtypes can be divided into two or three peak ranges.The metallogenic stages of the two subtypes overlap.The temperatures of the volcanic lava subtypes are lower and those of the subvolcanic subtypes are higher.The salinity of fluid inclusions in Xiangshan uranium ore field ranges from 0.88-22.00wt%.The peak value distribution is:Zoujiashan 2.98-3.28wt%,3.88-4.18wt%,Yunji 3.24-3.54wt%,3.84-4.14wt%;Julongan 18-20wt%;Shannan 5.97-7.97wt%,9.97-10.97wt%;Shazhou 11.2-14.2wt%,volcanic lava type and subvolcanic type with obvious difference,and the subvolcanic type has a high salinity.The density of Xiangshan ore-forming fluid ranges from0.6-1.1g/cm3.Zoujiashan deposit is 0.65-0.95g/cm3;Yunji deposit is0.75-0.95g/cm3;Julongan deposit is 0.5-1.15g/cm3;Shannan deposit is 0.64-1g/cm3;Shazhou deposit is 0.70-1.05g/cm3.The density of the two fluids changed slightly,and the whole fluids were medium and low density fluids.?2?According to Shao Jieliang,the average metallogenic pressure and depth of Xiangshan uranium deposit are calculated:Zoujiashan 340.3×105Pa,1.132 km,204.57×105Pa,1.132 km,204.57×105Pa,1.68km;Yunji 379.55×105Pa,1.55×105Pa,1.26km,721.12×105Pa,2.4 km;Julongan 139.3×105Pa,5.15km;Shannan506.8×105Pa,1.6 km,781 1.8×105Pa,2.6 km;Shazhou 619×105 Pa,2.11km 634×105Pa,2.11 km,914.4×105Pa,3.0 km.The metallogenic pressure and metallogenic depth vary greatly from deposit to deposit.Generally speaking,the mineralization depth of volcanic lava subtype is shallow,and that of subvolcanic rock is deep.?3?The phase composition of inclusions is mainly H2 and CO2 which is in a reducing environment.This mean is The source of ore-forming fluid is the same,and all of them are in reduction environment.?4?According to the study on the characteristics of fluid inclusions above,it is believed that the mineralization of Xiangshan ore-field uranium deposit has undergone two phases of secondary mineralization.The early metallogenic temperature is high,mainly due to the post-volcanic hydrothermal stage,with subvolcanic subtype uranium deposits as the representative.The late metallogenic temperature is relatively low,which is closely related to the heating of deep and large faults and the hydrothermal fluid formed by basin dehydration.It is affected by Zoujiashan-Shidong fault and represented by volcanic lava subtype uranium deposit.Early uranium mineralization is often superimposed by late uranium mineralization... |
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