Research On Metallogenic Series And Prognosis Of Endogenetic Metallic Deposits In The Middle Section Of Tianshan-Xingmeng Orogen

Metallogenic series study mainly is to reveal the laws of metallogenic processes in the four-dimension space, and deduce the relationship between the earth evolution and the distribution of the material constituting the earth. Such study has greatly improved our recognition of the global geologic laws, besides it also promoted exploration of the mineral resource. This dissertation mainly tries to study Metallogenic Series and Prognosis of Endogenetic Metallic Deposits in the South Mongolia-Erlianhaote-Dongwuqi district and the Huanggang-Ganzhuermiao district in the middle section of Tianshan-Xingmeng orogenic belt. My study based on the previous researches, conducting a detailed analysis on some important deposits where petrological and isotopic dating methods are employed to research the spatial and temporal distribution of the polymetallic deposits in the Tianshan-Xinmeng orogenic belt according to the metallogenic theory. The distribution pattern of various types of endogenic polymetallic deposits was thought as the marker and restriction condition of the variable tectonic setting, which provides a theoretical background to select optimum targeted large-scale polymetallic-intensive deposits in the middle section of the Tianshan-Xingmeng orogenic belt.The Tianshan-Xingmeng orogenic belt was formed mainly by the opening and closure of the Paleo-Asian Ocean from Neoproterozoic to Later Paleozoic, and then overprinted by the intra-plate structure along the continental margin of the west Circum-Pacific tectonic belt from Mesozoic to Cenozoic. Based on detailed analyses upon the tectonic and metallogenic evolution histories, we found a strong and complicated relationship between the tectonic evolution and metallogenic evolution both in space and time. As the result, we define two metallogenic belts in the area taking into account the geologic, geophysics and geochemistry, and remote sensing data: (1) Cu, Mo, Au, Fe, Zn, W, Pb, Cr metallogenic belt in the South Mongolia-Erlianhaote-Dongwuqi district to the north; and (2)Sn, W, Cu, Pb, Zn, Be, Ag, Fe, Nb(Ta) metallogenic belt in the Huanggang-Ganzhuermiao district to the south.After summarizing the characteristics of deposits and associated their tectonic setting, totally four metallogenic series and sub-metallogenic series are defined in the two metallogenic belts of the studied area according to the theory of metallogenic series:1. Three metallogenic series in the South Mongolia-Erlianhaote-Dongwuqi Metallogenic belt are as following:Ⅰ. The Later Devonian to the Early Carboniferous Magma-type Cr-Fe deposits complex related to ultramafic or mafic rock (ophiolite-type) in the Suolunshan -Hegenshan(Ⅰ).Ⅱ. The Later Devonian to Early Carboniferous Intermediate-acid granitoids-related Cu-Au-Mo deposits complex in the South Mongolia(Ⅱ).Ⅲ. The Yanshanian Granitoids-related Fe-Zn-Pb-Cu-Au-W-Ag deposits complex in the Erlianhaote-Dongwuqi district(Ⅲ).2. One metallogenic series is defined in the Huanggang-Ganzhuermiao Metallogenic belt, including two sub-metallogenic series.The Yanshanian Acid to intermediate-acid granitoids-related Sn-W-Cu-Pb- Zn-Be-Ag-Fe-Nb(Tb) deposits complex in the Huanggang-Ganzhuermiao district(Ⅳ), which is consisted of a Yanshanian Acid granitoids-related Sn-W deposits complex in the Huanggang-Ganzhuermiao district and a Yanshanian intermediate-acid granitoids-related Pb-Zn deposits complex in the Huanggang-Ganzhuermiao district.We carried out a detailed analysis of the typical deposits of different metallogenic series, especially the geological settings and ore-bearing structure in the Hegenshan Cr-Fe deposit, Oyu Tolgoi Cu-Au porphyry deposit, Chaobuleng skarn-type Fe polymetallic deposit, Shamai hydrothermal wolframite-quartz-vein W deposit, Dajing Sn polymetallic deposit, and Baiyinnuoer Pb-Zn deposit. Employing various methods of geological analyses such as isotopic geology, geochemistry, and inclusion-thermometric method, we documented the identity and differences of variable deposits.In the light of ore-control factors and metallogenic rules, Five regional metallogenic models have been established.From the view point of ore-controlling factors such as ore-bearing structure, mantle fluid, and interaction of crust and mantle, geological events, we have analyzed the spatial and temporal characteristics of ore distribution, concluding that the participation of the mantle fluid, as well as the heterogeneity of mantle-sourced material is strongly coupled in the ore mass-source with the formation of the large-scale deposit-intensive area. The Mesozoic tectono-magmati crock belt is a deposit-riched area. Geo-chronological data clearly demonstrated that the deposits formed mainly in two stages: Later Devonian to Early Carboniferous and Later Mesozoic. The later one is closely related to the Mesozoic tectonic transition event (140Ma) and the lithospheric thinning process (120Ma) in the North China. we consider that the coupling between the metallogenic event from 370Ma to 320Ma and the subduction of oceanic crust formed the first and second metallogenic series, and the coupling between the metallogenic event about in 140Ma and the large transition of tectonic system formed the fourth metallogenic series, and the coupling between the metallogenic event about in 120Ma and the process of lithospheric thinning formed the third metallogenic series in this area.In order to keeping up the Chinese requirement for mineral resource and the major goal of this study, we predicted and evaluated the prospect of Au, Ag, Cu, Pb, Zn, Sn, W and Mo deposits in the studied area based on the characteristics of the metallogenic belts in inner Mongolia. Total five B-grade potential areas, including Chaganaobaomiao Cu(Ag) polymetallic prospect(Ⅴ-1), Dalaimaio Cu(Ag) polymetallic prospect(Ⅴ-2), Aoyoute Cu(Ag) polymetallic prospect(Ⅴ-3), Chagantaolegai-Chaobuleng Ag-Cu polymetallic prospects(Ⅴ-4), Huanggang-Ganzhuermiao W-Sn, Pb-Zn polymetallic prospect(Ⅴ-5) are defined in the dissertation.Comparing the ore-froming geological conditions of the Eelianhaote-Dongwuqi area with those of the South Mongolia area, we believe that Erlianhaote-Dongwuqi area is also of advantage for economic ore deposits same as the South Mongolia. But their ore-forming elements assemblage is different. The deposits in the South Mongolia are mainly porphyry-related Cu(Au)-Cu(Mo) deposits hosted in the Later Paleozoic intermediate and acid granitoids with a much larger scale and relatively simple mineral assemblage. On the other hand, the deposits in the Erlianhaote-Dongwuqi area have a very complicated mineral assemblage and they were formed mainly in the Later Paleozoic and Later Mesozoic according to identified deposits and occurrences. The majority of economic deposits were mainly formed in Later Mesozoic, which is very likely related to the strong superimposing events of the west Circum-Pacific tectogenesis–magmatism–metallogenesis upon the eastern segment of the Paleozoic Tianshan-Xinmeng orogenic belt. In conclusion, during our reconnaissance in the Erlianhaote-Dongwuqi area, we should notice the similarities between the Erlianhaote-Dongwuqi and South Mongolia areas. More important, we also should pay more attention to the particularities in the Erlianhaote-Dongwuqi area.