Ore-forming Fluid Geochemistry Characteristics And Mechanism Of The Zhunsujihua Porphyry Mo Deposit In Erenhot-East Ujimqin Banner Metallogenetic Belt

Zhunsujihua porphyry Mo deposit is located in Southwest part of the Erenhot–East Ujimqin metallogenic belt.The newly discovered Mo deposit has a great scientific research and economic development.Combining the past research results,this thesis is themed by geochemistry of ore deposit in the Zhunsujihua porphyry Mo deposit.Through the data from petrography,fluid inclusions,and H-O-S-Pb isotopics,this paper discusses the possiblle origin about ore-forming fluid and ore-forming material.?1?Zhunsujihua porphyry Mo deposit occurs in the contact zone between the granite porphyry and Carboniferous-Permian Baoligaomiao Formation.Mo mineralization is mostly associated with silicification and phyllic.The hydrothermal alteration and mineralization processes can be divided into four types outward from the intrusive rock:potassic alteration?Stage I:quartz–K-feldspar±pyrite veinlets?,silicification?Stage II:quartz–molybdenite veinlets?,phyllic?Stage III:quartz–polymetallic sulfide veinlets?,and carbonatization?Stage IV:barren quartz–calcite veins?.?2?Four types of fluid inclusions?FIs?can be distinguished by petrography in hydrothermal quartz,including gas-liqiud two-phase inclusion?V-type:vapor liquid raio>50%;L-type:vapor liquid raio<50%?,mono-phase inclusion?PG-type:pure gaseous incusion;PL-type:pure liquid inclusion?.The homogenization temperatures in quartz of stage I,II,III,and IV vary from 300 to 520°C,230 to 410°C,170 to260°C,and 136 to 227°C,with salinities of 4.18–13.30 wt.%NaCl equiv.,2.07–11.10wt.%NaCl equiv.,1.74–8.95 wt.%NaCl equiv.,and 0.70–5.71 wt.%NaCl equiv.,respectively.The initial ore-forming fluids in this deposit are characterized by high temperature,and intermediate to low salinity belonging to an H₂O-NaCl system.?3?H-O isotopes reveal that the hydrothermal fluids of the Zhunsujihua porphyry Mo deposit have a dominantly magmatic signature with an input of meteoric water during the carbonate stage,the stable isotope(?³⁴S_V-CDT)from molybdenite and pyrite explain the ore-forming components were dominately sourced from magmatic reservoir,and the Pb isotope indicate that the ore-forming materials were dominantly derived from the upper continental crust mixed with a little mantle materials.In conclusion,Paleo-Asian Ocean subducted toward the North which gave rise to the melting of the upper crust.Magma rose gradually along the tectonic fissures and intruded into Carboniferous-Permian Baoligaomiao Formation metasanstone.Therefore,this processes resulted in hydrothermal alteration.The physicochemical conditions of hydrothermal system were changed when the ore-forming fluid flew,caused the deposit of ore-forming materials in the structural fracture,and formed the Zhunsujihua porphyry Mo deposit.