Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Xiaokelehe Cu-Mo Deposit In Daxinganling,Heilongjiang Province

Xiaokelehe Cu-Mo deposit is located in Xinlin Area of Daxinganling in Heilongjiang province.The geotectonic location is at the joint of Xing'an block and Erguna block.The metallogenic area belongs to the middle-north region of Daxinganling polymetallic metallogenic belt.It is a typical porphyry Cu-Mo deposit in this area.The mainly exposed strata in the area including Wolegen,Auspicious Groove Group and Big Net Group of the Lower Ordovician-Lower Silurian;Baiyingaolao Group of Upper Jurassic;Guanghua Group of Lower Cretaceous;Yaluhe Group of Upper Pleistocene series and Holocene series of Quaternary.The tectonics in the area is dominated by the faults,and the NE-and NW-trending faults are the main rock-controlling and ore-controlling structures in the mining area.The mainly magmatic rocks in the mining area are the intrusive rocks of Late Carboniferous,Late Jurassic and Early Cretaceous.And the Early Cretaceous granodiorite porphyry is the most important ore-bearing rock mass of the deposit,with the diagenetic age of 142.7Ma±.The magma originated from the partial melting of the copper-rich basic lower crust and the ancient molybdenum-rich silica-aluminum lower crust.The tectonic environment is mainly related to the combination of the back-arc extensional of the subduction of Paleo-Pacific plate and the compression-extension transition environment of the post-orogenic of Okhotsk.The mainly ore minerals in the mining area are chalcopyrite,molybdenite and pyrite,containing a small amount of magnetite,galena and sphalerite etc..Ore structure contains lumpy structures,veinlet structures and disseminated structures.Alteration showed typical surface-type characteristic,consisted of potassic zone-sericitization zone-propylitization zone from inside to outside.On the basis of petrographic studies,the fluid inclusions can be categorized as twomajor types: gas-liquid fluid inclusions and daughter-mineral-bearing three-phase fluid inclusions.The ore-forming fluid has the characteristics of medium-high temperature(180.9? to 478.3?)and high salinity fluctuation(3.53% to 54.75%).The metallogenic pressure of the deposit is about 4.4~33MPa,and the metallogenic depth is about 1~ 3.3km.The compositions of hydrogen-oxygen isotope of fluid inclusions reveals that they came from magmatic water,mixed meteoric water later.Sulfur isotope compositions showed that the minerals are partly derived from the granodiorite porphyry and partly from the basement or surrounding rock stratas.Through comprehensive analysis,we can draw a conclusion that Xiaokelehe deposit is a typical porphyry copper-molybdenum deposit.The study of mineralization enrichment regularity shows that the strata of Baiyingaolao Group of Late Jurassic and Guanghua Group of Lower Cretaceous is closely related to mineralization,and the main ore-controlling and ore-hosting structures of the deposit are NE-and NW-trending faults.The mineralization mainly occurs in the Early Cretaceous granodiorite porphyry and the surrounding rocks in the middle and deep underground,and the distribution characteristics of mineralization alteration show that the wall rock alteration which is the most closely related to mineralization is sericitization,followed by potassic alteration.The metallogenic elements are distributed in an irregular annular from the center to the periphery of the granodiorite porphyry,followed by Mo,Mo(Cu)to Cu(Mo)-Cu to Au,Ag,Pb,Zn.Through the study of geophysical and geochemical anomalies,it is concluded that the magnetic anomaly in the mineralized area is characterized by weak negative magnetic anomaly or weak positive magnetic anomaly or gradient zone,and the induced polarization anomalies are medium-high polarization and medium-low resistance,which are the comprehensive ore-caused anomalies.The molybdenum mineralization is visible from the deep to the surface of the concentration center of Mo abnormities in surface,and the chalcopyrite mineralization is poor from the deep to the surface of the concentration center of Cu abnormities in surface,which reflects that this area is a porphyry mineralization dominated by Mo elements.Above the comprehensive analysis of geological characteristics,regular of mineralization and concentration,geophysical and geochemical anomalies and otherelements of the deposit,five main prospecting target areas are delineated: 1.Target A: the inner and outer contact zones of the south-southwest side rock mass;2.Target B: the inner and outer contact zones of the northwest side rock mass in target A;3.Target C: the inner and outer contact zones of the north side rock mass in North area;4.Target D: the inner and outer contact zones of the northeast side rock mass in target A;5.Target E: the concentration center of Mo abnormities of the northwest side rock mass in North area.