Study Of Fluid Inclusion And Pyrite Typomorphic Characteristics In Deep Of The Dongping Gold Deposit,Northern Hebei,China.

The Dongping large gold deposits located in Chongli County,Zhangjiakou City,northern Hebei Province,which was firstly found among the alkaline complex in China.The ores is poor in sulphide and rich in telluride.In recent years,as the deep mining,ore types occur to transition from quartz-vein type to altered-rock type.Based on previous research and supported by "Study of mineral character and the mechanism of tellurium bearing gold deposits" project of China Geological Survey,this paper mainly studied the fluid inclusions and the mineral typomorphic characteristics in different occurrence of quartz and pyrite,and obtained the following understanding:(1)Fluid inclusions in quartz of the deep mineralization of Dongping gold deposit is very rich and characterized by multi-phase,large size,low salinity and abundant type.Three-phase CO2-rich inclusions is the main feature.Fluid inclusions of different mineralization stages have the distinctive characteristics.Early stage has a bigger quantity of inclusions,the majority are V-L inclusions and have a moderate salinity.The main mineralization stage has a small number of inclusions,the majority are three-phase CO2-rich inclusions and have a high salinity.Late stage is characterized by a large number of low salinity long cylindrical inclusions.The measured temperature from fluid inclusions was 270??330?.With the mineralization process,mineralization temperature has a decreasing trend,while the salinity first increased and then decreased.The mineralization temperature increased significantly with increasing depth.(2)The component analysis of pyrite showed that:extending longitudinally along the orebody,pyrite changed from S loss to Fe loss.Pyrite enriched in Te,Pb,Bi,Co,W and be poor in As,especially in pyrite from the orebody Quartz-polymetallic sulphides phases enriched in Cu,Pb,Zn,Te and other ore-forming elements.The pyrite of main mineralization stage has a LREE enrichment and a big Eu,Ce abnormal fluctuation.The pyrite in altered rock has a smooth chondrite-normalized REE distribution patterns.Co/Ni values and Co-Ni-As diagram partly indicate the genesis of magmatic hydrothermal,the overall plot dispersed.Contrast the REE distribution patterns of pyrite,silicified alteration of rocks and Shuiquangou alkaline complex,indicating ore-forming fluids may come or inheritance from Shuiquangou alkaline complex.(3)The study of pyrite pyroelectricity show that:the pyrite of Dongping gold deposit is N-type conductivity.Extending longitudinally along the orebody,the pyroelectric coefficient has a increased first and decreased then pulsation trend.The pyrite in quartz veins has a lower pyroelectric coefficient.High Co Ni,low As,and a higher mineralization temperature is the main reason of N-type conductivity of pyrite in Dongping gold deposit.The main mineralization temperature calculated using pyroelectric coefficient shows that temperature concentrated in 200??320?,that basically coincide with the measured temperature from fluid inclusions.(4)Pyrite trace elements show a combination of multiple ore-forming fluids,the assemblies of trace elements showed the great prospecting potential exists under 1184 m elevation.