Geological Characteristics And Prospecting Direction Of The Yuejinshan Cu-Au Deposit, Heilongjiang Province

The Yuejingshan Cu-Au deposit is located in the southwestern margin of theWandanshan terrane which is an important metallogenic belt with many minerals ofAu,Cu,Fe,Ni,W,Sn in northwestern Pacific tectonic domain. Wandanshan terranebelonging to Wandanshan-Sikhote Alin active belt is an accreted complex of thePacific plate subduction collage In the middle Triassic-early Jurassic and develops asuit of deep marine siliceous sediments and ophiolite formation. This metallogenicbelt mainly underwent multi-period intense tecotonic and magamtic activities inIndosinan and Yanshanian periods, which provides favourable conditions for regionalmineralization. This paper based on a large collection of data and systematic fieldresearch adopts the way of combining field geological observation with indoorsynthetic studies and multidiscipline with Petrology, ore microscopy, chronology,geophysic and geochemistry to systematically research the Ore-forming geologicalbackground, geological characteristics and metallogenic age of the Yuejing Mountaincopper-gold deposit and to discuss its genetic type and metallogenic dynamicsbackground,Meanwhile,extract the indication for prospecting and determine theprospecting direction combined with the metallogenic conditions and the existinggeological, geophysical and geochemical exploration data.The main outcropping strata in Yuejingshan Cu-Au mining area are upperTriassic Dababeishan Formation, Dajiahe Formation, upper Triassic-lower JurassicDalingqiao Formation plagioclase-amphibole schist, biotite-quartz schist, biotite-plagioclase-hornblende schist, marble; The outcropping igneous rocks includebasic-ultrabasic rocks, medium-acid intrusive rocks such as granodiorite, monzonitegranite, granite-porphyry, quartz diorite. The dominant structures are nearlyNE-trending compress-shear faults, NNW-NW-trending tension-shear faults, and theNNW-NW-trending faults are the main rock-control, ore-contro, guiding and hostingmine structure.The main mineralized type of Yuejinshan Cu-Au deposit includes contactmetasomatic skarn type iron ore, copper, porphyry copper and gold mine. Themetallogenic district contains three NW-trending mineralizing belts, and it has beendetermined6copper orebodies mainly hosted in granite-porphyry, skarns and theircontact zone;2gold orebodies hosted in granite-porphyry;13iron orebodies hosted inskarns at present.The morphology of ore bodies are mainly vein, lenticular, controlledby the NW construre. The main metallic minerals includes chalcopyrite and magnetite,and associated with chalcocite, azurite, limonite, pyrite, etc; Nonmetallic minerals aremainly diopside, epidote, chlorite, serpentine, actinolite, quartz, etc. The ore texturecommonly are euhedral-subhedral granular texture, anhedral granular texture,metasomatic relict texture. The ore structure mainly includes veinlet, veinlet-disseminated and massive structures. The wall rock alteration are mainly related to theore-forming include mussitization, tremolitization, actionlitization, epidotization,chloritization etc. Ore bodies are mainly pyritization and chalcopyrite. Obviously, thechalcopyrite of granite porphyry can be used as an important symbol of furtherexploration.The zircon U-Pb age for gabbro formed in an island-arc setting in this ore area is311±11Ma,belonging to Carboniferous, granodiorites are127±2Ma and129.11±0.76Ma, granite-porphyries are109.17±0.91Ma,111.5±2.0Ma,115.8±1.1Ma，monzonite granite is114.7±1.4Ma，and quartz diorite is116.0±1.3Ma. Suggest thatthe127~130Ma granodiorite is the host rock of Skarn type iron deposit,109~115Magranite-porphyry is the host rock of skarn type,porphyry copper-gold deposit. Both ofthem are formed in early Cretaceous, That means Yuejingshan Cu-Au deposit isformed in early Cretaceous. The rock geochemical analysis show that: these medium-acid magmas areperaluminous, ranging from high-K calc-alkaline to calc-alkaline series,relativelyenrichment of Rb,La,Nd,Hf and depletion of Nb,Sr,P,Ti. Combined with regionaltectonic evolution, consider their formation is mainly controlled by the subductedpacific plate, and they may originate subducted crust and sediments, also correlatedwith partial melting of the mantle wedge.The comprehensive analysis of extant geological, geophysical and geochemicalexploration data shows: single element anomalies of Cu,Au,Bi,Sn have a good set andalmost consistent concentration center in HS-1,HS-3anomalies.The Cu,Au have alarge anomaly and contain inner zone anomaly,which can be as the prospecting targetarea for Cu,Ａｕdeposits with the indicator elements of Bi,Sn.The Cu anomaly inHS-2is large and contains inner zone with multipoint anomaly,which can be as theprospecting target area for Cu deposits; Au,Bi,Sn single element anomalies in HS-4are in high intensity,all of those have a good set and inner zone anomaly,which can beas the prospecting target area for Au deposits with the indicator elements of Bi,Sn.