Ore–fluid Geochemistry And Metallogenic Epoch Of The Lingdong Gold Deposit And Lingyun Copper Deposit,Eastern Tianshan

Much more world-class gold deposits and copper deposits,which are the main part of the "Asian Golod Belt",have been found along the northern margin folding-thrusting fault zone of southern Tien Shan in the western region of Tien Shan.But few are found along that in the eastern region of Tien Shan.The Lingdong gold deposit with gold grade of 3.5g/t and the Lingyun copper deposit with copper grade of 1.4g/t,are new-discovered and explorating important deposits along the zone in the eastern region of Tien Shan.The gold orebody occurrs as lense hosted in tension-shear faulted crystal tuff of Early Devonian in the in the Yanxingshan brittle-ductile shear zone.The gold occurrence in ores is intergranule-,included-and nanometre-gold mainly in pyrite and pyrrhotite.The Lingyun copper deposit is bedded and lenticular in foliation or brittlement faulted crystal tuff.The ore-forming process of copper is divided into two stages characterized by quartz-sulfides paralleling to the foliation direction and ankerite-sulfides cutting the foliation direction.Re-Os dating of the Lingdong gold-bearing pyrite obtains an mineralization age of(306.0±4.2)Ma and the Lingyun chalcopyrite obtains an mineralization age of(297.9±3.4)Ma,which are almost consistent with the collision orogenic age after the closing of the southern Tien Shan ocean.The gold or copper mineralizqation might be closely related to the brittle-ductile deformation during the orogenic processes.The Linfdong ore ?34S ranges from 2.9‰ to 6.5‰,that is close to the tuff ?34S(from 3.3‰to 6.6‰),indicating that the ore sulpher was derived from the tuff.The Lingyun ore ?34S ranges from-14.4‰ to-6.6‰,indicating that the ore sulpher was derived from the reduction of sulfate in sea water.The Lingdong Pb isotopic compositons(206Pb/204Pb=17.160?17.483,207Pb/204Pb=15.369?15.736,208Pb/204Pb=35.749?38.879)and the 187Os/188Os(i)(0.680±0.039)of the gold-bearing pyrite in the ores indicate that the metal was sourced mainly from hosted tuff and partially from.deep reservoir by metamorphic fluids.The Lingyun Pb isotopic compositons(206Pb/204Pb=17.756?19.132,207Pb/204Pb=5.436?15.650,208Pb/204Pb=38.161?39.157)and the 187Os/188Os(i)(187Os/188Os(i)=18.54±0.67)of the copper in the ores indicate that the metal was sourced mainly from hosted tuff.For lingyun copper deposit,the main mineralization stage fluid is a type of middle-low temperature(130?370?),low salinity(1.5?14.9wt%NaCl),CO2-H2O-NaCl(±N2)fluid system related to the orogenic-metamorphism based on the microthermometry.Late mineralization stage fluid is a type of low temperature(135?150?),low salinity(1.7?5.0wt%NaCl)H2O-NaCl fluid system.The LingDong gold deposit and Lingyun copper deposit are brittle-ductile shear zone hosted orogenic deposit mineralizing under collision deformation setting.The orogenic deposit is showing a better exploration prospect along the northern margin folding-thrusting fault zone of southern Tien Shan in the eastern region of Tien Shan and should be paid much more attention.