Geochemistry And Genesis Of The Baoxingchang Porphyry Molybdenum-copper Deposit In Xiangyun, Yunna

The porphyry molybdenum-copper multi-metal mine in Jiudingshan is located in the copulae between west margin of the Yantze Platform and sanjiang fold system in Yunnan province,which sandwiched the triangle between NW jinshajiang-honghe fault and SN chenghai fault.By the collisional orogenics in Himalayan between indian continent and Eurasia,the magma was so activity and the structure was so complexity that made a series of porphyry deposits occurrence in this area.Baoxingchang ore block was the important porphyry copper molybdenum mining segment in Jiudingshan.In this paper,in order to identify the stage and sequence of magmatic activity,we study of the contact relation between the different types of porphyry and formation age,and divide into 4 stages in sequence:I stages was the orthophyre,quartz-orthophyre;Ⅱ stages was the porphyritic granite and lamprophyre in early stage;Ⅲ stages was the granite porphyry and lamprophyre in late stage;Ⅳ stages was the alkali-feldspar granite.The results of study show that the granite porphyry is the main metallogenetic rock body in the baoxingchang.The granite porphyry had a high potassium,alkalinity,LREE,SiO2,Al2O3,and low Yb that make it clear that it was adakite and had a strong capacity to caught and carried ore-forming element,and beneficial to molybdenum-copper mineralization.By study the isotope geochemistry and fluid inclusion in different ore block,analyze the material and fluid sources mineralization.Studies on stable isotopes in baoxingchang show that the metallogenic material such as S,Pb were came from hypomagma,ore-forming fluid wae came from Magmatic hydrothermal.The ore-forming fluid was M edium-high temperature and moderate salinity by the fluid inclusion study show.The ore is formed in the conditions of low depth,low pressure.The study of the ore-controlling factors indicate that the formation lithology,occurrence,chemical feature,alteration,metamorphic,structure are strong influence to the deposit forming.In Ⅲ stages of late Himalayan magmatism,the granite porphyry which rich in Mo,Cu and S intruded into porphyritic granite and lower Ordovician strata as apophysis or dyke.In the last stage of magmatic evolution,the residual magma-hydrothermal which rich in ore-forming elements gathered together in the top of granite porphyry and country rock.The metasomatic alteration was strong in this area,from granite porphyry to country rock,occur potassic,silicification,propylitization,sericitization in sequence.In granite porphyry occurred impregnated mineralize of molybdenite,chalcopyrite and pyrite.The quartz-vein type molybdenite and chalcopyrite were filling into joint fracture of porphyritic granite.In the contact zones of hornstone-skarn,formed stringer-disseminated type chalcopyrite and molybdenite.Above of the mineralization zone is an integrated zoning of mineralization-alteration of porphyry.