Study On The Mineralization Of Copper Polymetallic Deposits In The East Slope Of Southern Great Xing'an Range

The east slope of Southern Great Xing'an Range generally refers to the Paleozoic accretive orogenic belt south of the Hegenshan-Heihe fault and north of the North China Craton.According to the characteristics of topography and geomorphology,it can be divided into three NE trend extension area:the west slope,the main peak and the east slope.Among them,the Tianshan Tuquan metallogenic belt?east slope?develops polymetallic deposits dominated by copper.The study area is located in Hinggan League of the metallogenic belt.Typical deposits include Shenshan Fe-Cu deposit,Naoniushan Cu deposit,Lianhuashan Cu-Ag deposit,Agui Cu deposit and Budunhua Cu deposit.According to the geological characteristics,ore bodies and mineralization characteristics of the deposit,the copper polymetallic deposit in the east slope of southern Great Xing'an Range can be divided into three main types:skarn-?Shenshan Fe-Cu deposit?,porphyry-?Naoniushan and Budunhua Cu deposit?and hydrothermal vein-type?Lianhuashan Cu-Ag and Agui Cu deposit?.Among them,Shenshan Fe-Cu deposit occurs in the carbonate of Zhesi Formation or its contact zone with granodiorite.Its mineralization has experienced two stages of skarn and sulfide-quartz periods.The latter can be further divided into two stages:pyrite-chalcopyrite–molybdenite-quartz and barren sulfide quartz-carbonate;Naoniushan Cu deposit and Budunhua Cu deposit occur in the granodiorite porphyry and tonalite porphyry respectively,and the mineralization and orebodies are mainly vein or veinlet disseminated.Hydrothermal mineralization can be divided into four stages:arsenopyrite-pyrite-quartz,pyrite-chalcopyrite-pyrrhotite-quartz,pyrite-chalcopyrite–sphalerite-galena-quartz and sulfide quartz-carbonate;Lianhuashan Cu-Ag deposit and Agui Cu deposit occur in subvolcanic rock,the former ore body is controlled by NW fault,while the latter ore body trend is consistent with NE or near EW fault.Lianhuashan hydrothermal mineralization can be divided into four stages:arsenopyrite-quartz,pyrite-chalcopyrite-quartz,pyrite-chalcopyrite-sphalerite-galena-quartz and barren sulfide quartz-carbonate.Agui can be divided into four stages:hematite-magnetite-quartz,arsenopyrite-pyrite-chalcopyrite-quartz,pyrite-chalcopyrite-pyrrhotite-quartz and sphalerite-galena-quartz-calcite.The comprehensive study of fluid inclusions and stable isotopes shows that the ore-forming fluids and materials of each typical deposit in the study area are closely related to regional magmatism.The ore-forming fluid of Shenshan skarn deposit is a high temperature and high salinity NaCl-H₂O system hydrothermal fluid,which is derived from magmatic water and a small amount of meteoric water;The sulfur in ore-forming materials is derived from magmatic sulfur,and the lead is derived from crust-mantle mixed lead.The ore-forming fluid of porphyry Cu polymetallic deposits?Naoniushan and Budunhua?is a mixed solution of magmatic water and meteoric water.The ore-forming fluid is a high temperature high salinity NaCl-H₂O system hydrothermal solution,and the ore-forming material is derived from magmatic rock.The ore-forming fluid of the hydrothermal vein type Cu polymetallic deposits?Lianhuashan and Agui?is the medium-high temperature and medium-high salinity NaCl-H₂O system hydrothermal fluid.The ore-forming fluid is magmatic water in the early stage and a large amount of meteoric water in the later stage.The sulfur of metal sulfide in the deposit is derived from magmatic sulfur,and the lead is the mixed source of crust and mantle.Fluid boiling plays an important role in the main ore-forming stages of each deposit,which may be the key genetic mechanism leading to the precipitation of metallic minerals.According to the study of diagenesis and geochemistry of typical ore deposits,there are three stages of copper polymetallic mineralization in the east slope of Southern Great Xing'an Range:Early Triassic in Indosinian,late Jurassic and early Cretaceous in late Yanshanian.They are formed in the tectonic environment of the Paleo-Asian Ocean,the Mongolian Okhotsk ocean and the joint influence of the Mongolian Okhotsk ocean and Paleo-Pacific Ocean.According to the comprehensive analysis of regional tectonic evolution-magmatism-hydrothermalmineralization,the regional metallogenic model is established as follows:1)During the Early Triassic of Indosinian,the Lianhuashan Cu-Ag deposit was formed by partial melting of thickened lower crust under the influence of Paleo Asian Ocean closure?250Ma^?;2)In the late Jurassic of the late Yanshanian,the Mongolia Okhotsk ocean closed in a scissor like manner from west to east,and the upwelling of asthenosphere materials triggered large-scale magmatic activities in the area.The thickened lower crust is partially melted to form the parent magma of Shenshan granodiorite?160Ma^?,Budunhua tonalite porphyry?150Ma^?and Naoniushan granodiorite porphyry?140Ma^?.Three kinds of magma gradually developed into Shenshan skarn Fe-Cu deposit,Budunhua Cu deposit and Naoniushan Cu deposit through different degrees of crystallization differentiation;3)In the early Cretaceous,the Mongolian Okhotsk ocean and the Paleo-Pacific tectonic system jointly affected,and the lithospheric extension,and the Agui Cu deposit was formed after the mixing of crust and mantle materials?125Ma^?.