Study On The Geologic Characteristics And Genesis Of The ShangKeng-Guo Pb-Zn Deposit,northern Greater Khingan Range Metallogenic Belt

The Greater Khingan Range metallogenic belt,with huge resources potential,is one of the most important nonferrous minerogenie zones in China.Because of the increasing funding and the more and more attention supported by the government,the ore-searching achievements are remarkable.A series of medium-to large-type ore deposits(Pb5 Zn,Ag,Mo and U)have been discovered.The shangkengguo lead zinc ore is situated in the west side of the Great Khingan-minerogenie prospect of Mo,Pb,Zn,Ag and U,which has predictable ore-searching prospect.The deposit was located in pyroclastic rock in the Guanghua formation,lower Jurassic system.A volcanic edifice of central type eruption is the main Ore system,development of two volcanic eruption cycles.There has a crater situated in the centre,circular distribution,has to south lateral prostration.The migration pathway was provided by the volcanic edifice.The enrichment space of the lead and zinc deposit was provided by the faults zone around the volcanic edifice.There are about 15 concealed ore bodies in the shangkengguo lead zinc ore.Influenced by the F9 fault zone,these ore bodies are parallel vein distribution(NE 34°to NNE11°),the dip angle ranges from 56°to 80°.There are 3 types of ore mineral associations,including pyrite-sphalerite-galena-chalcopyrite,sphalerite-pyrite and sphalerite-sphalerite.The important indicator for depositare is the alteration association of the pyrite-chlorite-silicifica-tion and kaolinization.According to the rare earth elements of ores,hydrothermal solution was from the hypomagma.The differentiation of the ore-forming elements began in the silicate magmatic.The elements along the direction of ore body from high temperature to Iow temperature has obvious zonation,indicates that the ore-forming fluid is composed of a volcano along the tectonic outward migration.According to the isotope analysis of S and Pb,the ore-forming material of the deposit come from the hypomagma,Ore forming hydrothermal solution is a mixture of magmatic hydrothermal origin and atmospheric precipitation.According to the geothermometer analysis of sulfur isotope in galena and blende,the mineralization temperature was 267?350?,indicating a mesothermal temperature deposit.The field investigation and indoor comprehensive study show that the deposit is a continental volcanic hydrothermal type deposit.In Late Mesozoic,the hypomagma remelted the basement.As a result,some of the lead and zinc in the basement were mixed with the hypomagma.The differential magma was erupted during the paroxysmal eruption.In the later period of the eruption,volcanic feeder was sealed by the rhyolite porphyry filling.In a relative stable condition,the sufficient differentiation induced the ore-forming elements accumulating in the fluid.In the last phase of the volcanism,the subvolcanic rock and the surrounding rock were broken and the fracture was formed due to the repeatedly fault activities.Then,the space was prepared for the mineralization.The ore-forming hydrothermal solution permeated into the factures and the lead zinc ore was formed by the metasomatism and filling function.