Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Harizha Ag-Cu Polymetallic Deposit In Eastern Kunlun Orogenic Belt,Qinghai Province

Hariza Ag-Cu polymetallic deposit is located in Dulan area,Qinghai province.The geotectonic location of the deposit is in the granite belt of Middle Kunlun uplift basement,eastern region of eastern Kunlun orogenic belt.The major outcropping layer of mining area is Paleoproterozoic Jinshuikou Group and Late Triassic Orashan Formation.The dominating trend of fracture is NE-SW direction.Magmatic action in mining area is intense and the rocks formed from Caledonian to Yanshanian are exposed in the mining area.The research revises the rock-forming age of Late Hercynian porphyaceous moyite and granodiorite(using zircon u-pb dating),whose ages are 417.5±1.5Ma and 235.1±0.85 Ma respectively.Zircon U-Pb age of gabbro vein close to ? mineralized zone is 430.2±1.5Ma.Ore-bearing country rock of ? ore belt should be Orashan Formation crystal tuff,not "granodiorite porphyry" as previously thought,whose rock-forming age is 233.9±3.6Ma instead of being formed in Late Hercynian.5 ore belt and 3 mineralized zone are delineated in the mining area and ?,? ore belt are the main metallogenic belt in the area,which have 49 ore bodies.The ore bodies appear in vein shape,strictly controlled by fault structure,showing the dominating trend of NW direction.The incline of ? ore belt is SW,while the incline of ? ore belt is NE.There are two types of mineralization in the mining area,one is silver-copper polymetallic mineralization,which is the major mineralization type in the area,and the other is independent silver mineralization,which is distribution limited.The ore minerals include arsenopyrite,pyrite,sphalerite,chalcopyrite,galena,pyrrhotite,tetrahedrite,pyroxenite,acrosite,freibergite and a small amount of covellite,limonite and marcasite.The main texture of ore includes granular texture and metasomatic texture and the main structure of ore includes vein structure,disseminated structure and massive structure.The main alteration of country rock includes silicification,serictization,chlorinization,kaolinization,potassic alteration,carbonation and minor epidotization.Mineralization in the mining area is closely related to silicification and serictization and it is divided into three metallogenic stages,namely early hydrothermal mineralization stage,which is Ag-Cu polymetallic mineralization period,late hydrothermal mineralization stage,which is independent silver mineralization period,and supergene oxidation stage.Temperature measurement of fluid inclusions showed that the main metallogenic stage fluid of Hariza Ag-Cu polymetallic deposit has the feature of medium temperature(220-240? in ? ore belt and 200~220? in ? ore belt),low salinity(3.53~15.21wt% Na Cl eqv in ? ore belt and 0.70~19.55wt% Na Cl eqv in ? ore belt),low density(0.63~0.95 g/cm3 in ? ore belt and 0.63~0.99 g/cm3 in ? ore belt).For ? ore belt,the ore-forming pressure is 52-102 MPa and metallogenic depth is 5.76~8.34 Km.For ? ore belt,the ore-forming pressure is 38~84MPa and metallogenic depth is3.8~7.5km.The results of hydrogen and oxygen isotope analysis indicated that the ore-forming fluid was mainly composed of mantle juvenile water and metamorphic water,added a small amount of meteoric water.the results of sulfur and lead isotope analysis indicated that the metallogenic material came form the deep,mixed with crustal material.The research found zircon in the hydrothermal quartz vein of major metallogenic stage,whose U-Pb age was 223.2±1.6Ma,The age can represent mineralization age,namely late Triassic epoch.Combined with regional tectonic evolution,we conclude that Hariza Ag-Cu polymetallic deposit was formed in the late indosinian,in the setting of changing from compressional regime to extensional regime after continental collision orogenesis of eastern Kunlun orogenic belt.It is a tectonically controlled mesothermal vein Ag-Cu polymetallic deposit,superimposed late low temperature hydrothermal vein type silver deposits.Systematically summarizing the law of mineralization,we think that fault structure controls the form,occurrence,distribution of ore bodies,topoenrichment of mineralization and spatial positioning of industrial ore bodies.It is mainly manifested in that the ore body is concentrated in the NNW direction of fault strike horizontally and in the position with steep inclination vertically.Indicating that ore controlling stucture is dextrorotatory normal fracture.Analyzing the denudation and preservation conditions in this area,There is a postmetallogenic fault(F4),which is located between ? ore belt and ? ore belt,whose trend is nearly parallel to that of vein.Tectonic movement of F4 leads to differential denudation of geological bodies on both sides.The preservations of ? ore belt and ? ore belt are different.? ore belt in the west of fault underwent larger denudation,whose position was relatively elevated,while ? ore belt in the east of fault underwent smaller denudation,whose position was relatively decline.According to the characteristics of differential denudation,We conclude that ? ore belt can be treated as the root of ? ore belt,whose potentiality of exploration is not promising.? ore belt has a big deepening,which has larger metallogenetic potentiality,and prospecting should be focused on the deep of ? ore belt.