Comprehensive Study On Metallogenic Model Of Liwu Ore Section In Liwu Copper Mine,Jiulong County,Sichuan Province

Liwu Copper Mine in Jiulong County,Sichuan Province,formerly known as Liwu Copper Mine,is located in Jianglang dome metamorphic core complex on the western margin of Yangtze Platform.It has been over 60 years since the exploration and development of the deposit,and now it has been classified as a crisis mine.Although the exploration geological work has been completed in Liwu copper deposit,the investigation and research on regional mineral geology is not very high,and the previous studies on the mineralogy of Liwu ore block are also lacking.Although many units and scholars have done research work on it,the genesis of its deposit has been controversial,and there is basically no comprehensive research on systematic deposit geochemistry and metallogenic model in Liwu ore section of Liwu copper mine field.In view of this,the comprehensive study on metallogenic model of Liwu ore block is selected as the topic,based on the macroscopic geological characteristics of the ore deposit,combined with the study of mineralogy,fluid inclusion analysis and stable isotope geochemistry,so as to understand the intersection relationship and generation sequence of ore minerals,divide metallogenic stages and periods,determine metallogenic fluid,source of ore-forming materials and metallogenic age,and finally establish the genetic model of the ore block,providing reference for peripheral and deep prospecting.Through the study of ore micro-mineralogy,it is found that the gangue minerals in Liwu ore block are mainly pyrrhotite,chalcopyrite and sphalerite,and the gangue minerals are quartz,muscovite biotite,etc.It can be seen that there are obvious filling metasomatic texture,metasomatic residual structure,solid solution separation structure,etc.,which have obvious structural characteristics of hydrothermal filling metasomatic origin.By testing the uniform temperature and freezing point of 64 inclusions in 7inclusion slices,it is found that the freezing point temperature ranges from-1.5?to-14.1?with an average of-7.05?,while the uniform temperature ranges mainly from 158.3?to 222.1?,with an average temperature of 188.55°C and 265.4?.Through the test data of uniform temperature and freezing point,it is concluded that the salinity of inclusions is between 2.57%and 17.87%by weight.The ore-forming fluid density of Liwu ore block is estimated to be 0.91g/cm³by Na Cl-H₂O solution inclusion density formula,while the density is estimated to be 0.955g/cm³by using the graphic casting point of fluid system density calculation model.According to the previous empirical formula,the pressure range of Liwu ore block is between318.43×10⁵Pa to 959.98×10⁵Pa.Through the study of hydrogen and oxygen isotopes of ore,it is found that?¹⁸O value is in the range of-0.90?7.33‰,the average value is 3.105‰,and?D value is in the range of-61.2?-75.8‰.It is found that the main sources of water in ore-forming fluid are magmatic water and metamorphic water,and atmospheric precipitation may be added in the later stage.Through the study of ore sulfur isotope,it is found that?³⁴S is between 2.79‰and 8.95‰,different metal sulfides have the same sulfur source,and mantle sulfur is inferred as the main sulfur source.According to the results of lead isotope test,the composition test shows that the values of ²⁰⁶Pb/²⁰⁴Pb are between 18.179 to 18.537,²⁰⁷Pb/²⁰⁴Pb are between 15.751 to 15.935,and²⁰⁸Pb/²⁰⁴Pb are between 38.890 to 39.277.Compared with the previous test results,it is found that the lead in Liwu ore block is mixed lead,mainly in crust and a little in mantle,and the lead source comes from ore-bearing metamorphic rock series with high probability.After comprehensive analysis,it is considered that Liwu ore block has the characteristics of multi-stage mineralization,and should be a metasomatic metamorphic deposit filled with medium-high temperature hydrothermal solution.The ore source bed first appeared due to submarine volcanic eruption-sedimentation,but it was not enriched and integrated in a large area.Later,it was mineralized under the joint influence of hydrothermal activity and metamorphism,and it belongs to becoming a deposit.