| The Fuanpu Molybdenum deposit, which belongs to the northern margin of the NorthChina craton, east of the Xing’an Mongolian orogenic belt and the western outer edge ofthe Pacific subduction zone, is located26km east away from Shulan City, Jilin Province.Regional stratigraphic development is complete， but stratigraphic distribution isdiscontinuous due to the late tectonic magmatic activity, from old to new, there are strataof Paleozoic Permian,Mesozoic Triassic,Jurassic,Cretaceous and Cenozoic,stratigraphyscattered distributed in the ‘sea of granite’.Ten ore bodies are found in the mine,ore typeis quartz vein type.Ore minerals aremolybdenite,pyrite,chalcopyrite,pyrrhotite.Ore extures contains crystal structure,metasomtic structures,anhedral ranular textures,euhedral-hypidiomorphic textures,crushing textures.Ore structure contains vein and veinlet structure and disseminatedstructure.Alteration consist of K-feldspar,sericitizaton,silicification.The mineralizationperiod can be divided into four phases:quartz-magnetite mineralization stage,quartz-molybdenite mineralization stage,quartz-polymetallic sulphide mineralizationstage,carbonate formation stage.The Bangzishan granitic pluton is the proximal enclosing rock of FuanpuMolybdenum Deposit, which composed of porphyroid biotite monzonitic granite，monzonitic granite,bi-granodiorite and granite porphyry.The LA-ICP-MS zircon U-Pbdating of porphyroid biotite monzonitic granite gives an age of179±2Ma，and172±1Mafor granite porphyry，which corresponds to the formation of the Bangzishan granitic pluton in the Middle Jurassic.indicateing products of the Early Yanshanian periods. Thetrace element is ch SiO2content of the stick was61.89%-71.06%granite, is relatively high,high Al2O3content of14.54%-17.11%, K2O content of2.28%-4.38%, Na2O content of3.74%-7.82%, Fe2O3content of2.34%-5.91%, MgO content of0.55%-2.37%aracterizedby a strong enrichment in large ion lithophile elements and incompatible elements, such asRb, K, and U, Th. depletion in Ba,Ta,Nb,P,Ti;. The REE patterns demonstrate LREEenrichment and HREE deplition, with weak negative Eu anomalies. These results indicatethat the Bangzishan granite is the metaluminous-weakly`peraluminous I-type granite ofhight-K cale-alkaline serise in category and it is the product of the westward subduction ofthe Paleo-Pacific plate.Analytical studies on the isotope geochemistry (including H, O and S isotopes) showthat the minerals were from multi-source of the mantle and upper crust ore-forming,fluidswere magmatic water.The source of the ore-forming fluids in theore-forming process isnot entirely magmatic water which is the main source, but withmeteor water mixed.The study of the Fuanpu molybdenum deposit fluid inclusions system acquiresimportant metallogenic physicochemical parameters: fluid inclusions mainly werecontaining gas-liquid two-phase inclusions;the size of inclusions was3-22μm,andinclusions was in the form of oval, circular, quadrilateral, irregular form. The temperatureof various stages of fluid inclusions in quartz veins was110.2℃~476℃, and salinityranged from3.2wt%~17.6wt%. Laser Raman spectroscopy of inclusions indicate thatthe principal gas-phase components are H2O,with a small amount of CO2and CH4.Theore-forming pressure can be calculated to almost40to52MPa, the ore-forming depthranges from4.8to6.0km. The ore-forming fluid in the main mineralization stage ischaracterized by middle-high temperature and middle-low salinities.Study on the genesis of the Fuanpu molybdenum deposit, mineralization time shouldbe Middle Jurassic.indicateing products of the Early Yanshanian periods.We foundFuanpu molybdenum deposit unlike typical porphyry molybdenum deposit,itscharacterized by orebody not occur in porphyry,the deeper depth of mineralization,orestructure in veins, veinlet, disseminated.Therefore,we believe the genetic type of the Fuanpu molybdenum deposit is stockwork deposits associated with plutonic intrusions inthe metallogenic rock of calc-alkaline series. |
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