The Contribution Of Mantle Component To Diagenesis And Metallogeny

Yanbian area of Jilin province is located on the overlap position of Paleo-Asian Ocean Orogenic domain and Paleo-Pacific Ocean domain,and since Mesozoic,it was mainly affected by the subduction of Paleo-Pacific Ocean Plate.In this contribution,we selected the Shiguo intrusion,Gaoling intrusionand Nongping Au(Cu)ore deposit to explore the contribution of mantle material to the petrogeny and metallogeny.Shiguo granodiorite shows high silicon,alkalis and low Ta/La ratios,and enriched in LILEs and LREEs,and depleted in HFSEs and HREEs with features of typical arc rocks.Shiguo has Sr-,Ba-and Eu-anomalies,which indicate the early fractional crystallization.Shiguo granodiorite has high zircon saturation temperatures,which shows that the granodiorite was generated by high heat fiuxed melting.Shiguo is featured by low initial 87Sr/86Sr,positive ?Nd and young model age with deplting Hf isotopes,and these features indicate that Shiguo formed by the basaltic magma of high heat flux underploted the juvenile crust reslting in the partial melting.The MME(173.4± 1.2 Ma)and host of Gaoling(171 ± 1.4 Ma)have similar ages.Through the petrology,geochemistry and Hf isotopes,we regard the MME as the product of incomplete mixing of crust and matle magma,and represts the mantle end-member.The zircon in host has the lowest ?Hf(t)of-3.5,which represents the crustal end-member,however,zircon in the MME has the highest ?Hf(t)of 7.1,which represents the depleted mantle component.The geochemistry features of Gaoling show the addition of subducting sediment and plate-derived fluid in the source area.According to the estimation of Sr-Nd isotopes,mantle component may account for 60%-70%of the source.Nongping ore-bearing porphyry has high Sr/Y and(La/Yb)N ratios,which are similar to the adakite.The features of petrology and geochemistry show the the fractional crystallization of amphibole,magnetite,sphene and zircon lead to the magmatic evolution to the high Sr/Y ratios.Nongping ore-bearing porphyry formed at 95.6±1.2 Ma,with chronology of other ore deposits in the same area,we find that these mineralization events mainly happened on 110-90 Ma,which may represent a new metallogenic peak.The Nd/Ta and Lu/Yb ratios of Nongping porphyry are similar to that of the continental crust,but the Mg#,Sr and Ba content and Zr/Hf ratios indicate that role of mantle material in the formation of Nongping porphyry.Sr-Nd-Hf isotopes of Nongping porphyry show the addition of mantle fluid in the early stage of minerlization,and as the evolution of the ore-bearing fluid,the crustal material was added in it.In summary,Shiguo and Gaoling show the reworking of crustal material and magmatic mixing are the important mechanism of crustal evolution,mantle component provide heat and material.And the study of Nongping porphyry deposit show the importance of mantle fluid to the formation of the Nongping Au(Cu)deposit.