Minerals, Alteration And Fluid Characteristics Research Of Southern Tiegelong High Sulfidation Epithermal-porphyry Cu (Au) Deposit, Tibet

Southern Tiegelong Cu (Au) deposit (Rongna) within Duolong ore cluster, Bangonghu-nujiang ore belt, is a porphyry-high sulfidation deposit, which is the first discovered high sulfidation epithermal Cu (Au) deposit in Tibetan plateau with huge geological and economical value. Through systematic geological suveys, core logging, section measure in the filed and microscope identification, EPMA, and fuild inclusion temperature test in the laboratory, this thesis focuses on some researchesof ore minerals%alteration assemeblages、alteration distribution and fluid inclusion to ensure the deposit types, build the alteration modol and discuss the genesis primarily. There are some As-bearing minerals like enargite and tennantite; Cu-S series minerals like covellite, digenite, chalcocite, djurleite, spionkopite, geerite etc. that are typical high-very high sulfidation station minerals;Cu-Fe-S series minerals like chalcopyrite and bornite as well as molybdenitedeveloping in the deposit.Alteration is characterized by typical alunite-kaolinite-dickite etc. clay minerals in acid environment, and rutile, anatase, anhydrite, goyazite,pyrophyllite, diaspore etc. as well. Alteration distribution is consist of potassic-phyllicalteration-chlorite alteration-alunite-kaolinite/dickitealteration-leach belt from deep to shallow position of the mine.All the ore minerals and alteration information indicate that high sulfidation system is located at the shallow place while the porphyry system is located at the deep place of the mine. Thus, Southern Tiegelong is a deposit that high sulfidation overlaying porphyry deposit. One group of fluid that enrich volatiles like SO2±H2S、Cl2and another group of fluid that has many daughters with high temperature, high salinity are the keys to the formation of minerals and alteration of this mine. The fluid that helps form advanced argillite at shallow place is acid high fO2and middle-low temperature(mainly239℃-292℃), low salinity (mainly0.35%-4.18%); but the fluid in deep porphyry is daughters-bearing high temperature(mainly285℃～390℃and404℃～430℃), high salinity (mainly32.39%～35.99%nd32.39%～38.94%). The mixture of magmatic hydrothermal fluid that enriched in vapor(mainly SO2、H2S and Cl2) and meteoricwater is the key to help form acidic, high fO2,middle-low temperature and low salinity fluid that contribute to the formation of high sulfidation epithermal alteration and mineralization. Additionally, my work estimates the pressure and the mineralization depth, and the results indicate that the advanced argillite alteration formed at the depth of approximate500-600m; and the porphyry at shallow place intruded to about1.2km deep, while the deep porphyry intruded to2.7km beneath ancient ground. Thus we can infer that the Southern Tiegelong deposit had been lifted around500-1000m after the mineralization and alteration happened. There are typical porphyry-epithermal system in Duolong ore cluster region contains specific minerals、alteration and fluid, which indicate some other similar porphyry-epithermal deposits could be discovered in this region.