Geological Characteristics And Genesis Of The Guliku Gold Deposit In The North Part Of Great Xing'an Range

The Guliku gold deposit is located in the north of Heilongjiang Province,the eastern part of Xingmeng orogenic belt and in the northeast of Xing'an block.The metallogenic division belongs to Nenjiang Paleozoic and Mesozoic Mo,Au,Cu,Pb,Zn(Ag)metallogenic belt.On the basis of systematic collection of previous research results,through field investigation and laboratory test and analysis,the author systematically studied the metallogenic geological background,metallogenic geological characteristics,metallogenic magmatic rock characteristics,stable isotope composition of ore,fluid inclusion characteristics,etc.,and determined that the deposit is a low sulfide epithermal deposit.The research achievements are as followsThe gold mineralization of guliku gold deposit can be divided into two types:carbonate bearing plagioclase quartz vein type and reticular vein silicified rock type.The ore bodies are vein like,arc vein like and banded,occurring in volcanic rocks of Early Cretaceous Longjiang and Guanghua formations and in the contact zone with metamorphic rock series of Neoproterozoic early Cambrian basement Luomahu Group.According to the mineralization characteristics,the ore types are divided into gold,gold and silver,and silver types.The main metal minerals are composed of pyrite,argentite,native silver,chalcocite,and silver tetrahedrite,and trace chalcopyrite,galena,sphalerite,chalcocite.The ores display euhedral subhedral crystal structure,metasomatic structure,solid solution separation structure,vein,network vein and breccia structure.The wall rock alteration of the mining area is developed,and the main types of wall rock alteration include silicification,plagioclasization,potassic,sericitization,chloritization,carbonation,kaolinization.In terms of spatial distribution,the alteration is divided into three zones:albite silicified inner zone,sericite pyritization middle outer zone,kaolinization qingpansitization outer zone.Gold silver mineralization is closely related to albitization and silicification alteration.The rhyolites related to mineralization,characterized by high potassium and rich alkalinity,is rich in large ion lithophile elements(LILE)such as Ba,Rb,Th,U and light rare–earth elements(LREE),inaddition,it is depleted in high field strength elements(HFSE)such as Nb,P and Ti and heavy rare–earth elements(HREE),The fractionation characteristics of LREE and HREE are obvious,showing a right dipping REE distribution pattern of LREE enrichment and HREE depletion.The weak negative Eu anomaly indicates that the magmatic evolution is in the early stage In this process,the fractional crystallization of plagioclase is not obvious.The results of mineral inclusion study show that the ore-forming fluid of guliku gold deposit belongs to medium low temperature(180?260?),low salinity(1.33?6.12%Na Cl eqv)and low density(0.64?0.96g/cm³)fluid.The ore-forming depth is 0.531?1.130km.S isotope analysis shows that the sulfur of guliku gold deposit mainly comes from upper mantle and deep crust.According to zircon U-Pb dating,the rhyolites are(127.2±2.8)Ma and(130.9±1.3)Ma,respectively.According to the above research,the ore-forming material of the deposit mainly comes from the upper mantle and deep crust,the ore-forming fluid is mainly meteoric water,mixed with magmatic hydrothermal solution,belonging to the Na Cl-H₂O system hydrothermal solution;the ore-forming age is the late Early Cretaceous,and the deposit is a low sulfide epithermal deposit.The guliku gold deposit was formed in the extensional tectonic environment in the late Early Cretaceous,which is related to the lithospheric extension after the closure of the Mongol–Okhotsk ocean.