Study On Deposit Genesis And Mineralization Enrichment Regularity Of Mizhananeng Pb-Zn Deposit In Yushu,Qinghai Province

Mizhananeng deposit is a newly discovered lead-zinc deposit in Duocai.Through preliminary estimates,the 334 resources is 35,700 tons,where Pb resources is 34,400 tons,Zn resources is 0.24 million tons and that of Ag is 740 kg.It has a significant potential for prospecting,and it is the potential zone for the search of medium-sized carbonate-type lead-zinc deposit.However,the theoretical research in this area is very weak,the uncertainty of deposit type and characteristics of ore-controlling rules restrict the progress of prospecting.Therefore,it is necessary to carry out comprehensive study on the deposit and improve the overall research degree of the deposit to provide theoretical guidance for the further investigation and a basis for prospecting breakthroughs in Duocai.Based on the field work,we figured out the regional geological background,the geological characteristics of the mining area and the deposit.Through the analysis of the fluid inclusions,isotopes characteristics and electron probe of single mineral,the physical chemical condition of ore deposition,source of ore formation fluid and materials were found out.With all that,the genesis of mineral deposit was evaluated and the law of mineralization enrichment was summarized.The research area is located in the north of the northwest of the Sanjiang,which is China's emerging important mineral resources base.Its tectonic position is located between the Kekexili-Jinshajiang suture zone and the Wulanwula-Yushu fault,distributed in the northwest west of the Xiagenglong-Batang.It belongs to the Tongtiehe copper,lead and zinc Metallogenic subzone of the Sanjiang polymetallic metallogenic belt.The orebodies are mainly found in the Jiapeila group of Jiezha of Late Triassic.The lithology contains the middle-thick limestone section and the thin limestone-sandstone interbedded rock section,and the middle-thick limestone section is the main ore-hosting rock.The Mizananeng lead-zinc-mining area is located in the centre of Mizananeng anticline.The F2 fault,located in the south wing,is the main transmitting ore structure and local ore-bearing structure.The F2 fault controls the distribution of ore body ?,which distributed in the in the fault zone and its adjacent rock fissures.The anticline is affected by the northeast-southwest thrusting force,which is easy to produce empty in the anticline.It provides a favorable place for the ore-forming,which may be the ore-bearing structure of the deposit.The next specific working position should focus on the turning point of the double anticline.The fluid inclusions of Mizananeng lead-zinc deposit are mainly the gas-liquid two-phase brine solution inclusions.The ore-forming fluids were low temperature(120?190 0C),low salinity(0.8?2.4%NaCl and low density(0.89?0.96 g/cm3),and the temperature and salinity were slightly decreased with time.The pressure and depth of main ore formation process are 7.94?11.25 Mpa and 0.79?1.22 km,respectively.The atmospheric precipitation was the main source of ore formation fluid.The sulfur isotopic characteristics indicate that the source of sulfur is inhomogeneous.The sulfur of two barite sample are mainly derived from marine evaporite,and the source of that of four sulfides is characterized by both the characteristics of the sedimentary and magmatic sulfur,mainly magmatic.Lead isotope results show that lead has mixed lead characteristics,which is consistent with sulfur isotope results.The electron probe analysis of pyrite,sphalerite and galena show that the pyrite and sphalerite are characterized by mix of hydrothermal and sedimentary genesis,which is consistent with the results of sulfur and lead isotopes.In summary,through the analysis of the fluid inclusions,sulfur-lead isotopes and electron probe,the genesis of the deposit belongs to the shallow-type low-temperature hydrothermal type.By comparing the same type of deposits in the same area,such as the Duorirong and East Mozazhua lead-zinc deposit,the Mizananeng lead-zinc deposit has similar ore geological characteristics,which means Mizananeng was formed at the same period(34 Ma).And the age is close to that of Zhayong Cu polymetallic deposit,which indicate the formation Mizananeng lead-zinc deposit was related with the magma activity of the same period and formed at Oligocene.