Characteristics Of Ore Minerals And Genesis Of Luobuzhen Pb-Zn Deposit Of The Gangdese Belt,Tibet

The Luobuzhen Pb-Zn deposit,located in the western part of the Gangdese metallogenic belt of Tibet,is still lack of systematic studies on the metallogenic environment and evolution characteristics.This thesis takes Luobuzhen Pb-Zn deposit as the research object,on the basis of summarizing the geological background and previous research results of Luobuzhen Pb-Zn deposit,through field geological survey and drilling core catalog and detailed sample collection work,combined with the interior of thin section analysis,electron microprobe analysis,sulfur isotope geochemistry characteristics and other modern analysis and testing technology,Characteristics of ore minerals and sulfur isotope geochemical characteristics of the Luobuzhen ore deposit have been studied and the following results have been obtained:?1?The mineralization process of Luobuzhen Pb-Zn deposit can be divided into Hydrothermal and Epigenetic period.according to the spatial distribution characteristics of ore bodies,ore types,ore texture and mineral interaction.The hydrothermal period is the main mineralization stage of the deposit,during which hydrothermal activity led to the migration and precipitation of a large amount of metallic elements.Based on the above division,the hydrothermal period is divided into quartz-arsenopyrite-pyrite stage???,quartz-pyrite-galena-sphalerite-chalcopyrite stage???and quartz-calcite stage???.?2?According to the Electron probe data of sphalerite,arsenopyrite,pyrite,chalcopyrite and hessite,it shows that the sphalerite,the major and trace element characteristics indicate it formed in the hydrothermal environment,is belong to the quartz-pyrite-galena-sphalerite-chalcopyrite stage.The arsenopyrite,which belongs to the quartz-arsenopyrite-pyrite stage,the ratio of Co/Ni in arsenopyrite and Crystal structure characteristics shown that it is shown that the arsenopyrite has the characteristics of medium-low temperature hydrothermal.According to the different types of pyrite minerals,structure,mineral assemblage and stage of mineralization,the deposit is divided into two generations.the electron probe data shown that the metallogenic temperature in the first phase to the second phase has increased,the sulfur fugacity has increased,and the spatial depth has gradually deepened.However,in general,the two metallogenic stages still have the characteristics of medium-low temperature hydrothermal origin.In addition,the physical and chemical properties of hessite indicateed that the deposit has the characteristics of medium low temperature hydrothermal mineralization.?3?According to the sulfur isotope geothermometer,the temperature of pyrite-galena is 296?.The temperature of pyrite-sphalerite is roughly the same as that of pyrite-galenaat296?;thesphalerite-galenatemperatureis279?;the pyrite-chalcopyrite temperature is 275?;the chalcopyrite-galena temperature is 218?,show that the ore-forming temperature ranges from 218?to 296?.It can be seen from the above characteristics that the ore-forming temperature of the Luobuzhen Pb-Zn deposit belongs to medium-low temperature.?4?Sulfur isotope analyses in combination with other available data indicate that?³⁴S values of sulfur isotope in sulfides are-3.5‰⁰.7‰,the range is 4.2‰,with an average of-0.5‰;the?³⁴S value of pyrite range from-1.1‰to 0.7‰with a range of1.8‰,with an average of-0.13‰,the?³⁴S value of chalcopyrite is-0.8‰;the?³⁴S value of sphalerite is-1.2‰‰;the?³⁴S value of galena is-3.5‰,the sequence of sulfide enrichment is pyrite>chalcopyrite>sphalerite>galena.Indicatedthat sulfur isotopes in these minerals were in an equilibrium state during their formation.Comparing the?³⁴S values of different types of sulfur isotope reservoirs on the earth and the typical deposits on the Gangdese metallogenic belt,it is believed that the sulfur in the Luobuzhen Pb-Zn deposit belongs to magmatic sulfur.