The Geochemical Features Of PGE And Semimental Elements From The No.2 Orebody In Jinchuan Cu-Ni Sulfide Deposit,Gansu Province And Its Significance In Ore Genesis

The Jinchuan super-giant Ni-Cu-(PGE)magmatic sulfide deposit,located at Jinchang,Gansu province,China,is the third largest in the world and the largest mining camp in China.Its special geological characteristics?huge economic values and prospecting potential have largely attracted many attention of geologists and ore deposit scientists from all over the world.And in recent years,much studies about the genesis of Jinchuan intrusion and ore bodies and their chronology have been done,which make us understand the metallogenic model of Jinchuan deposit completely and deeply.The No.2 ore body in Jinchuan deposit is the object of this research.which systematically analyze the contents of the platinum-group(Ir?Ru?Rh?Pt?Pd)and semi-mental elements(As?Bi?Sb?Se?Te)of sulfide ores sampled from the western(38 line)?middle(41 line)?eastern(52 line)part of the No.2 ore body in the eastern intrusion of Jinchuan,Combine our new data with data published previously,the goal is to recognize the spatial variation regulation of these elements and its indicative significance to the formation of the No.2 orebody in Jinchuan deposit.According to the study about the geochemical characteristics of Ni?Cu?PGE and semimetal elements in the sulfide of ores from Jinchuan No.2 orebody,and comparison with the No.1 and No.24 ore bodies,theses new recognition and achievements below can be concluded:(1)The value of Cu/Pd of sulfide ores in Jinchuan deposit is obviously higher than the mantle value,which indicates that they are the results of sulfide second segregation.Meanwhile the value of Cu/Pd of sulfide ores in No.2 ore body is also higher than it in No.1 and No.24 ore body,which suggests that the parental magma of No.2 ore body had suffered higher degree prior sulfide segregation.(2)On a 100% sulfide basis,the positive correlation between the contents of IPGE and PPGE?the decoupling between Pd/Ir with semimetal elements?the low Pd/Ir(<100)and similar primitive-mantle normalized PGE patterns of sulfide ores of No.2 ore body imply that the concentrations of PGE and chalcophile elements is restrained by the segregation of sulfide,but little affected by fractional crystallization of sulfide melts and alteration of post thermal fluids.(3)The similar contents of Ni?Cu?PGE and similar primitive-mantle normalized PGE patterns of sulfide ores in the eastern(26 line)of No.1 ore body and the western(38 line)of the No.2 ore body suggest that they are belong to one magma conduit..(4)The contents of ?PGE on a 100% sulfide basis decrease gradually from the west to the east of the ore body,and the simulated calculation of sulfide segregation show that the R dropped from the west to the east of the ore body during the second sulfide segregation.it also can be concluded that the ore-bearing magma flowed from the west to the east during the diagenesis(5)The massive ores are the consequence of late injection of sulfide melts,thus the deep of No.2 ore body have the potential to find new mental resources,such as the base of the net-textured rich ores?the contact between the host rock and the country rock and the fractures in the foot wall.