Mineralization And Metallogenic Model Of Tianbaoshan Cu-Pb-Zn-Mo Polymetallic Deposit, Yanbian

Containing our research results and the data from previous, we studied the Xinxing deposit and Dongfeng molybdenum deposit in Tianbaoshan polymetallic deposits. Based on the study of Metallogenic Geological Settingd and ore deposit geology, Mainly discusses the Characteristics of Fluid,S,Pb isotopic characteristic of ore mineral., The ore-forming material sources, Ore-forming Fluid Evolution and metallogenic mechanism of Xinxin deposits and Dongfeng deposits. Based on the above knowledge, we established Metallogenic Model. In this thesis,the conclusions and achievement as following were given out:(1) Tianbaoshan polymetallic deposit belongs to Ya Lujiang river—Mingyue Metallogenic belt .The geotectonic position of the area is located in the joint of Xingkai-Jiamusi Block , North of China Craton,and southeast Dunhua-Mishan fault. Early Paleozoic Qinglongcun Group and Wudaogou group is the oldest strata in this area. Magmatic Rocks are developed well in the area. The age of these magmatic rocks are from Caledonian to Yanshan stage. Hercynian granites are widely distributed as batholith. Mesozoic granites occurs only mostly in stocks and veins. At the same time ,Mesozoic volcanic eruption is very intensive in this area.(2) Xinxing deposit is strict controlled by faults, hosted in the breccia pipe which located in the joint of EW fault, NW fault and SN fault. Research shows that the major ore minerals are sphalerite, galena, chalcopyrite , with minor amounts of pyrite. The types of wall rock alteration are epidotization, sericitization, silication and carbonatization. According to the texture and structure, mineralization stages are divided into: quartz-pyrite stage, quartz-calcite-metal sulfide stage and calcite-metal sulfide stage.Dongfeng deposit shows the character of strata-bound. hosted in the formation contacted with late Hercynian quartz monzonite diorite. The shapes of ore bodies are stratiform, stratiform-like, consistent with the stratigraphic occurrence. Research shows that the major ore minerals are sphalerite, galena, chalcopyrite , molybdenite, associated with pyrite, and pyrrhotite. The types of wall rock alteration are mylonitization epidotization, sericitization, silication and carbonatization. According to the texture and structure, mineralization stages are divided into: volcanic exhalation period and hydrothermal period, which in turn include quartz - sulphide stage and carbonate - metal sulfide stage.(3)Xinxing deposit has two fluid types: gas-liquid phase inclusions (Ⅰ-type inclusions), three phase inclusions containing CO2 (Ⅱ-type inclusions). ClassⅠfluid inclusions accounted for the total content of 85% ~ 90%, the size was between3um ~ 10um, gas-liquid ratio is between 10% ~ 45%, homogenization temperature is at 130℃～330℃, the main ore-forming stage of 190℃~ 260℃, wt﹪NaCl of inclusions mainly concentrated in the 4 ~ 7, density mainly concentrated in between 0.8 g/cm3 ~ 1.00g/cm3. ClassⅡinclusions between the size of 4um ~ 8um, volume ratio of CO2 to the inclusion was 30% ~ 50%, CO2 partial homogenization for the gas. homogenization temperature is at 270℃~ 340℃, and there were no classⅡinclusions, salinity mainly concentrated in the 1.03 wt% NaCl ~ 2.62 wt% NaCl, density range of 0.37 g/cm3 ~ 0.41 g/cm3. Ore-forming fluid show that Characteristics of medium temperature - low pressure - low salinity. The most fluid inclusion type of Dongfeng molybdenum deposit was gas-liquid phase inclusion, and some of the pure liquid inclusions. Gas-liquid phase inclusions accounted for the total content of 60% ~ 70%, the size was between2um ~ 4um, the gas-liquid ratio is between 5% ~ 10%, homogenization temperature is at 101.2℃～189.4℃, the temperature show that the ore-forming characteristics: 150℃~ 190℃temperature stage and 100℃~ 140℃temperature stage. Salinity mainly concentrated in 13wt% NaCl ~ 19wt% NaCl. Content of pure liquid inclusions accounted for 30% ~ 40%, the gas-liquid ratio is 0%. Such inclusions generally oval-shaped and irregular-shaped strip, the individual generally smaller, in general <2 um, the freezing point observation difficult. Ore-forming fluids in general show low-temperature - low pressure - in the nature of salinity.(4) Studying the S, Pb isotope Characteristics of Xinxing deposit and Dongfeng molybdenum deposit, the result shows that:①The most ore minerals of Xinxing deposit and Dongfeng molybdenum deposit are sulfide minerals, the main sulfur to form sulfide, basic no sulfate minerals, so the sulfur isotopic composition of sulfide minerals can be similar to the the isotopic composition of the ore-forming fluids. The average of Xingxin deposits between -4.15‰~ -1.37‰, and the average changes in Dongfeng molybdenum deposit is at -0.46‰~ +1.45‰, all fall into the range of mantle-derived sulfur (0±3‰), indicate that S from the deep magma.②The Pb isotopic of Xinxin deposit and ore deposits Dongfeng molybdenum deposit show the characteristics of anomalous lead, while the deposits and granite in the 207Pb/204Pb-206Pb/204Pb diagram show a good linear relationship. Through the lead structural model the source region and lead structure identification chart analysis, that: It is believed that the Pb of Xingxin deposits from the lower crust and mantle ,and Pb of Dongfeng molybdenum deposit from the upper crust and lower crust, and they have some of the links with granite.(5) From the research of the element in strata and magmatic rocks showed that: the Cu, Pb, Zn, Ag of strata in mining area was significantly higher than the regional average formation, magmatic rocks in mining area occurred local enrichment of Cu, Pb, Zn, Ag elements or leached by fluid after they formation. So we think that the strata and magmatic rocks in mining area proved metallogenic material to Xingxin deposit and Dongfeng molybdenum deposit. The result equates the characteristics of S,Pb isotope.(6) TheⅠandⅡfluid inclusions of Xinxing deposit with a distinct uniform temperature, salinity, density and composition, at the same time , the two types of fluid inclusions without the Characteristics of boiling and mixing, so that these two types of inclusions product in different stages of the fluid. Combining with the deposit in granodiorite, the metallogenic material from the mantle magma, the fluid contain CO2. We think that the ore-forming fluids are the magmatic fluid containing metallogenic material. The mineralization is later than the formation of breccia pipe. The fluid metasomate the breccias and wall rocks while it passed the breccia pipe. The main reason of metallogenic material precipitated is metasomatism.The fluid of Dongfeng molybdenum deposit also without the characteristics of boiling, the water-rich, low temperature and low salinity which it shows are markedly different the magmatic fluid with gas-rich, high temperature, high salinity. But it is similar with hot brine in strata. It output in the contact zone of magmatic rocks and strata or strata, the metallogenic material from the mantle magma, and the composition of S is obvious alreratic volcanic rocks, so that the fluid is formation water. The formation water containing a little of magmatic water were heated by the magmatic rocks, then it cycled and metasomatismed strata, the metallogenic material precipitated in weak zone in strata and fracture zone.