Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Chayong Cu Polymetallic Deposit,Yushu,Qinghai Province

Chayong Cu polymetallic deposit is located in Yushu of Qinghai Province.The tectonic position is located in a compressed zone between Gondwanaland and Eurasia.Which belongs to a part of Tethys Himalaya tectonic domain.It locates to between Longmu Co-Lancang River suture zone and Jinsha River suture zone which belongs to polymetallic metallogenic belt.The mainly exposed strata in the area is the second formation complex of Triassic Batang group.widely distributed magmatic in the study area.Distribution area is small within the mining area.Mainly intrusive rocks,there are the granodiorite,quartz diorite and gabbro.The gabbro is closely related to the copper mineralization,showing the vein copper ore body is cut through by gabbro,and indirectly limit the metallogenic age.Geological studies indicate that it belongs to continental tholeiitic basalt which is formed in a post-orogenic extensional environment after the Indian-Eurasian plate collision.At present,The zoneidentifiedore body of CuI-1?CuI-3?CuI-4?Cu-Pb-Zn-Ag-MoI-5.Ore minerals are chalcopyrite,molybdenite,pyrite and so on.Ore textures are mainly metasomatic textures,dissemination and massive textures and so on.The main ore structures are sparse disseminated structure,disseminated structure,fine(net)veinstructure.Thewall rock alteration are mainly silicification,biotitization,silky mica-quartzite and so on,Which is characterized by linear alteration,showing high temperature-low temperature gradient characteristics.We used several trenchs revealed lots of vein and lenticular ore bodies,which are controlled strictly by fracture structure.The study of the fluid inclusions shows the type is simple.Quartz fluid inclusion homogenization temperature of 363.7?~415.9?,salinity of 0.53 to 6.29wt%NaCl,density of 0.53 to 0.59g/cm3 in the main mineralization stage.Raman analysis of fluid composition,the gas phase composition of the ore-forming fluidsmainly H2 O,CH4,N2,followed for CO2 is a H2O-NaCl-CH4-N2±CO2 system.The pressure can be calculated to almost 50 to 60 MPa,the depth ranges from 5.63 to 6.22 km.The sulfur isotopes is mainly reductive sulfur from Triassic layer,and mixed with some magmatic sulfur.The lead isotopes mainly from upper crust,mixed with some lower crust.According to the dating results from gabbro,limits on the metallogenic age,belongs to the Himalayan period.The deposit is formed in a post-orogenic extensional environment after the Indian-Eurasian plate collision.Combined with the above characteristics,we determine its genetic type as meso-hypothermal vein-type deposit.Mineralization enrichment studies found that the deposit is controlled strictly by fracture structure.On strick,the ore body is relatively rich in the east-west fault and the intersection between east-west and north-west fault.On vertical,rich in soft occurrence.Element zoning composition is Mo-Cu-Pb,Zn,Ag from deep to shallow.On horizontal,ore veins is a series of north-east equidistant parallel distribution.The direction is NWW on lateral,in which Mo-Cu-Pb,Zn,Ag on Element zoning from east to west,which is the direction of further prospecting on high grade of Pb,Zn,Ag on the west.On the contrary,there is an information that the existence of deep hidden intermediate-acid small intrusive bodies on east.