On The Relationship Between Magmatic Rocks And Metallogeny In The Jinchiling Gold Deposit,Zhaoyuan Area, Shandong Province

:Jinchiling deposit is located in north central of Zhaoyuan-Laizhou metallogenic belt. Gold deposits here appear to have interesting spatial relationship to the contact zones between various intrusions within the granitic complex, as well as to be accompanied by multiple dikes. Many other gold deposits in the Jiaodong area have similar occurrence which suggests that there is a genetic-relationship between gold mineralization and the formation of granite complex. Up to date, however, this genetic relationship is still controversial. In order to reveal whether the composite rock pluton have influenced the ore-forming process, whether dikes have contributed to gold mineralization, as well as the geological significations of above phenomenon, this paper discussed the relationship between the formation of magmatic complex and the ore-forming process through detailed petrogenesic-metallogenic studies of the Jinchiling deposits, including field geological investigation and mapping, structural geologyanalysis, petrographic study, trace element geochemistry, fluid inclusion study, and the stable isotope analysis, etc..After re-encoding of the geological and geochemical data of Linglong granite composite bodies (GCB), the author believes that both Linglong type granite and Guojialing type granodiorite are formed by repeated crustal melting in the Mesozoic, and are good examples of "the in-situ melting theories". Linglong type granites are formed in the Late Jurassic whereas Guojialing type granodiorite are formed in the Early Cretaceous, the difference of their lithology is related to their melted source rocks.The author rebuilt the inner relationship of repeated crustal melting from Late Jurassic to Early Cretaceous. The repeated crustal melting, occurring in the Late Jurassic, contains three phases melting interface(MI). After eroding, the bottom surface of earliest MI was cropped out on higher topography of granite body at the North and South ends, whereas the top surface of third MI formed on lower topography of granite body and the second MI was located between the first MI and the third MI. The Early Cretaceous’repeated crustal melting contains at least four phases MI, the generalspatial distribution of the different phases MI is from old to new from the top down.The characteristics of petrography and geochemistry show that the dikes are various and diversified. K-Ar dating shows that most dikes have formed between120Ma and104Ma,the author believes that the various dikes in the granite complex should have been formed by small scale melting from multi-sources, and is a good example of post-orogenic dike complex.The characteristics of hydrogen and oxygen isotope show that the initial ore-forming fluids of Jingchiling gold deposit originate from magmatic system, and the later ore-forming fluids have mixed meteoric water. The result of sulfur isotopic shows that the range of δS34is similar with the Precambrian metamorphic rock series in the Jiaodong region, which suggests that the sulfur sources has the inheritance, direct source is granite and indirect source is repeated melting of Precambrian metamorphic rock series. Through analysis of type, temperature, salinity and composition of fluid inclusions, it conduct that the ore-forming fluids should be derived from magmatic system, which experienced fluids mixing or water-rock interaction in main metallogenic stage, and evolved poor CO2, low salinity and low-temperature fluid with meteoric water as the main body in late metallogenic stage.The metallogenic model of Jinchiling deposit has been built through analysis of temporal and spatial relationship between granitoid complex, dike assemblage and gold mineralization, as well as relationship between magmatic rock-forming mechanism and gold mineralization mechanism. The gold, occurred in Precambrian layers, was re-activated and re-mobilized, migrated and finally enriched in the suitable location of fault zones after repeated crustal melting in the late Yanshanian. The multi-sourced dikes could partially contributed ore-forming materials during their emplacement. The whole process, which involves multi-source ore-forming material, caused the multi-stage formation of gold deposits in the part of this area.