Characteristics Of Temporal And Spatial Evolution And Polymetallic Mineralization Of Early Mesozoic Granites In Southeastern Xiaoxing' An Mountains

The Southeastern XiaoXing'An Mountains are a part of grand- scale of"Sea of Granites"in Northeast Mesozoic located in Eastern XingMeng orogenic belt. In this dissertation, based upon the research in the temporal and spatial evolution of Early Mesozoic Granites,genesis and the formation of tectonic background and petrogenesis and mineralization in the region, the metallogenic series of ore deposits were divided, diagenetic and metallogenic model were established, and metallogenic prospective zones were enclosed and also prospecting potentiality was evaluated. It had the following main achievements and understandings:1. Through the research of Porphyritic monzonitic granites,generally grown mafic microgranitoid enclave(MME)among porphyritic monzonitic granites,catagenesis rock dyke - pyroxene diorite and diorite porphyrite etc intermediate-basic dykite group as well as macroscopical and microcosmic,major- trace elemental and isotope characteristics, it had new understandings that the rocks had obvious crust-mantle magma mixing genesis and also it had new achievements that Zircon U-Pb dating age of Porphyritic monzonitic granite LA-ICPMS was 191.4~231Ma,dating age of hypomagmatic dyke - pyroxene diorite was 186.3~207Ma (/bulk Rb-Sr isochron), and Zircon U-Pb dating age of Porphyritic monzonitic granites was 190.8~202.08Ma.2. Aluminium type A2 syenite - alkali feldspar granite in Late Triassic-Early Jurassic period were firstly determined and Zircon U-Pb dating age was 175.1~214Ma, the genesis of the rocks was related to partial melting of materials from ancient modification of crust under the basic magma underplating and common control in a certain crust-mantle magmatic mixing and differentiation and so formed the tectonic environment of collapse and expansion after continental collision.3. In the research area the granites in Early Mesozoic was evolved from porphyritic monzonitic granite,monzoporphyry - orthophyre to aluminum type A2 syenogranite - alkali feldspar granite and type-A alkali granite. The rocks were formed in the Late Triassic-Early Jurassic period. This explained that this area had experienced the sequential evolution of tectonic background of continental geodynamics from continental collision to the collapse after collision after the final closure of the Paleo-Asian Ocean, it implied that this region had entered into an epicontinental accretion tectonic setting in marginal-pacific tectonic domain, and it brought huge significance in ensuring the conversion time between Paleoasian tectonic domain and Paleo-Pacific tectonic domain.4. Based upon the granites in Early Mesozoic in temporal and spatial evolution,genesis and tectonic background and the characteristics of petrogenesis and mineralization, the metallogenic series of ore deposits were divided into two sub-class metallogenic series of ore deposits which were Mo-Au-Pb-Zn-Fe sub-class metallogenic series of porphyritic monzonitic granite from collision-transition period after collision and Fe-Pb-Zn-Mo sub-class metallogenic series of alkali feldspar granite from collapse after collision; and it was indicaated that the differentiation of mineralization of two sub-class metallogenic series of ore deposits was related to ore-forming tectonic background and the properties of magmatic source, petrogenesis, the blending ratio of magmatic material in crust mantle, intensity of blending, emplacement depth of magma and so forth, and for the first time the model of petrogenesis and mineralization was established from the underplating granites in Early Mesozoic.5. Among Xiaoxilin lead-zinc orefield, it had been achieved the LA-ICPMS Zircon dating age of fine - medium granule porphyritic monzonitic granite which was closely related to mineralization was 197~207Ma and indicated new understandings of overlaying lead-zinc mineralization in Late Triassic-Early Jurassic period.6. In conclusion, in summarizing the strata,igneous rocks,geological analysis of structural ore-control,metallogenic regularity and various types of prospecting indicator in the research area and in combination with the comprehensive characteristic research of geology, geophysical prospecting, geochemical prospecting and remote sensing, four Grade-I and one Grade-II and one Grade-III metallogenic prospective zones of Fe polymetallic deposit and gold deposit were enclosed, which were related to the Early Mesozoic granites. The analysis of metallogenic regularity and prospecting potentiality was conducted in the metallogenic prospective zones.