Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Sanalongwa Copper Deposit,Yushu City,Qinghai Province

The main Sanalongwa copper deposit in Qinghai province is located in the southwest Sanjiang area,North West.The tectonic site is located in the southern margin of the Eurasian continent,the western margin of the Yangtze and the east of the Yangtze dam,the eastern part of the Dongba-Lancangjiang suture zone.The strata exposed in the mining area are mainly the Late Triassic Pondang volcanic rocks and limestone groups,and a small amount of sedimentary rock barite is exposed.The ore-bearing strata are mainly bentonite tuffs,Ansan granulite tuffs,basaltic tuffs and so on.The zircon U-Pb age of the basaltic tuff is 237.5±2.9Ma.The geochemical results of the basaltic tuff show that the Mg# value is 50.49 on average,which is larger than the Mg#value of the mantle magma.The ? Eu range is 1.08 ~ 1.69,which indicates that the source region has no separation of the plagioclase;(Th/Ta)PM ?(La/Nb)PM value is3.97~11.66,the average value of(Th/Nb)PM is 6.67 and the TDM1 value is 792-886 Ma,which indicates that the original magma of the rock should originate from the depleted mantle and the crustaceous matter Or enrichment of mantle components.The rocks have the characteristics of calcareous basaltic arsenic,and have some properties of the mid-ridge(MORB).In the southeastern side of HS46 anomaly area,one(?CuPbZn)ore body is circled,the ore body is controlled to a length of 1600 m,width of 4.94-13.34 m,Cu grade of 1.55%,Pb grade of 2.94% and Zn grade of 4.69%.Located in HS37 abnormal area,circle a copper(? Cu)ore body,ore body length greater than 200 m,thickness 6.71 m,Cu grade0.84%.Field investigation and indoor analysis to determine the two sets of mineralization system: the channel around the obvious mineralization,the surrounding rock volcanic rocks;sedimentary facies developed a variety of barite rocks,iron siliceous rocks.The ore minerals of the two ore bodies are mainly chalcopyrite,pyrite,galena and sphalerite.The ore structure is mainly self-shaped structure,semi-self-shape-its crystal structure,vein-like structure,the residual structure of the structure,the structure of the structure.Ore structure is mainly disseminated structure,striped or striped structure,vein or network vein structure,thin film structure.The alteration of surrounding rock is mainly silicification,chlorite(curtain)petrochemical,sericite,carbonation and so on.And it is determined that the deposit has experienced two periods of mineralization during the hydrothermal spill deposition and phenotypic oxidation.Fluid inclusions studies have shown that,(180~220?),low salinity(1~5wt%NaCl),low density(0.84~0.92g/cm3)fluid,and the ore-forming fluid in the sedimentary facies barite(140~160 ?),low salinity(8.8~9.6wt%NaCl),low density(0.92~0.94g/cm3)fluid.The sulfur isotope study shows that the mean value of sulfur isotope ? 34 S in chalcopyrite is-1.9,and the variation of sulfur isotope ?34S in pyrite is in the range of-0.6~-0.3,which indicates the characteristics of deep magmatic sulfur or mantle source sulfur.The results of the ?34S analysis of the barite sample are 15.5 and 15.8,which represent the characteristics of the Late Triassic marine evaporite ?34S.The formation of the metallogenic age for the formation of the surrounding rock basaltic tuff formation era,that is,late Triassic.According to the comprehensive analysis,the Sanalongwa copper deposit is a depleted sulfur-type hot water jet deposit.Through the geological model,geochemical exploration model and so on themineralization enrichment of the deposit analysis,(Au,Ag,Cu,Pb,Zn),and the anomalies of geomagnetic anomalies are the key areas of ore prospecting.