Geological Characteristics And Metallogenic Regularity Of Mo(Cu) Deposits In Antu Area, Jilin Province

The research area is located in the southern section of Xiaoxing’anling-Zhangguangcailing molybdenum metallogenic belt, with favorable metallogenicgeological conditions and abundant molybdenum resources. Based on the systematicgeological prospecting data, this thesis summarizes the metallogenic regularity of Mo（Cu）deposit in the research area preliminarily, by means of the study on geologicalcharacteristics, metallogenic physicochemical conditions, diagenetic and metallogenicages and ore-forming materials sources of typical deposits（Shuangshan, Liushengdian）,and comparison with the similar type deposit in same metallogenic belt.The Shuangshan deposit and Liushengdian deposit,15km away from each other,belong to medium-scale molybdenum deposit newly discovered in Antu area of JilinProvince. Shuangshan deposit contains valuable copper resource, but Liushengdiandeposit is a single-molybdenum deposit. Those two deposits which were formed in thesame geological background and geological conditions are adjacent in the space,controlling by EW, NW and NE trending faults. Mo（Cu） ore bodies mainly occur inmonzonitic granite porphyry which accompanies typical altered zoning. There are closespatial relationship between Mo（Cu） mineralization and the quartz-sericite zone; Themajor mineralization types are stockwork type and veinlet-disseminated type. The mainmetallogenic stage of Shuangshan deposit consists of quartz-molybdenite-pyrite stage andquartz-polymetallic sulfide stage, but Liushengdian deposit only develops quartz-molybdenite-pyrite stage. The analysis of fluid inclusions indicates that the types of fluid inclusions formed inthe main metallogenic stage of Shuangshan deposit are liquid-rich phase inclusions （typeL）, halite-bearing three-phase inclusions （type S）, vapor-rich or pure vapor inclusions（type V） and CO₂-bearing three-phase inclusions （type C）. Homogeneous temperature andsalinity decrease gradually from quartz-molybdenite-pyrite stage to quartz-polymetallicsulfide stage; Only liquid-rich phase inclusions （type L） and vapor-rich or pure vaporinclusions （type V） can be distinguished from the main metallogenic stage ofLiushengdian deposit that is characterized by more various vapor-liquid ratio. Shuangshandeposit and Liushengdian deposit were formed in mesothermal and hypabyssalenvironment, accompanying widely fluid boiling in the main metallogenic stage. Theore-forming fluid belongs to the NaCl-H₂O-CO₂±CH₄system.Chronological data show that the weighted mean U-Pb age of zircons of theore-forming monzonitic granite porphyry from Shuangshan deposit is （178.42±0.73）Ma（MSWD=2.1） and the Re-Os isochron age of molybdenites collected from ores is（174.5±2.0）Ma （MSWD=1.5）. The Re-Os isotopic dating for the Liushengdian depositgives an isochron age of （169.36±0.97） Ma（MSWD=0.73）. Both Shuangshan deposit andLiushengdian deposit were formed in Early Jurassic period, and they are resulted fromtectonic-magmatic-metallogenic events in the same period. The Re values ranged from29.49to71.67μg/g and from9.88to11.37μg/g, indicating the ore-forming materialsderived mainly from the crust and mixed with a small amount of mantle substances.In sum, Mo（Cu） deposits in Antu area belong to the quartz monzonite porphyry type.The Mo（Cu） mineralization occurred in the Early Jurassic period and Mo（Cu） deposits aredistributed along the regional deep faults, controlling by the secondary fracture system.The ore-forming materials derived mainly from the crust, and fluid boiling and mixingwere key mechanism for Mo（Cu） deposition and enrichment. The monzonitic graniteporphyry of Shuangshan deposit possesses the potential for both Mo and Cumineralization, and shows metallogenic specialization for porphyry Mo（Cu） deposit.Based on the study of metallogenic regularity, this thesis also summarizes prospectingcriteria for Mo（Cu） deposits in the region in the aspect of regional structure, magmatic rocks, wall rock alteration and mineralization type and so on.