Study On The Geological Features And Metallogenic Regularity Of Hezhengdaxia Copper-gold Deposit, Gansu

Hezhengdaxia copper-gold deposit locates in front mainland basin structure area ofmiddle Qinling of western Qinling,Shangdan suture zone and Mianlue suture zone of westQinling, The junction position of the north fault fold belt and middle chasmic trough of westQinling orogenic belt.The mining ore stratum were around sea and land Permian and a part of clasticcarbonate clamp，There was a well gas liquid cover effection. Diorite exposed rock in Miningarea，gold deposit was controlled by rock fracture structure belt and surrounding rock contactzone.Ore belt distributes nearly east-west direction,as same as regional structure direction,asingle ore body mainly was controlled by subprime south-north direction extensional structureand rock and surrounding rock contact zone. The pisolitic and lenticular orebody produced inrock mass surrounding rock（marble）contact zone（skarn belt）around（skarn type copper-goldmine body）and（hydrothermal vein type copper-gold mine body） distributed insidesouth-north direction（almost south-north direction） tensile fracturesd of dioritic rock.Useful elements priority are gold and copper in mining area,mineral generation methodwere given priority to with contact metasomatiem and fissure filling.Block structures、Smallvein disseminated and vein structures are the main structures of ore. ore minerals are mainlypyrite、chalcopyrite、chalcocite，gangue mineral are mainly skarn minerals、quartz and calcite.gold spreading in minerals such as pyrite chalcopyrite and bornite with granular,star point,finevein,inclusion gold and crystalcrack-gap gold forms. Surrounding rock alteration typesinclude skarn alteration、potassium and carbonatization.There are skarn、skarn alterationmarble and all kinds of hornfels in skarn alteration belt,it is a seris typical calcic skarn givepriority to diopside、calcium iron（aluminum）garnet、vesuvianite and scapolite.According to study the space distribution,shape and attitude of the ore body,thecharacteristic of petrology,petrochemistry and lithogeochemical,ore-forming diorite overall isrich potassium granite,belongs to shoshonite series, Its rare earth elements distribution patternis enrichment light rare earth and loss heavy rare earth model,distribution curve to theright,the fractional degree is higher,europium negative anomaly.Trace element of rock massenrichment large ion incompatible elementRb、Ba、U、K、Sr,loss the high field strength element Nb、Ta、Zr、P、Ti characteristics.Na/Ta ratio on average was15.99，numerical is big，show that diorite evolution degree is not high，reflecting the rocks may be derived from uppermantle or lower crust rocks.according to the analysis results of fluid inclusions,microscopictext and gas liquid phase composition,ore-forming fluid of sulfide stage of daxia gold-copperdeposit middle temperature and a low salinity of H2O-NaCl-CO2system.There is a deepmantle source characteristics of ore-forming fluid; according to the analysis results of sableisotopes of sulfur,hydrogen,oxygen, it is mainly composed of nature magmatic fluid early anda small amount of minerization build fluid in the late.Based on the SHRIMP zircon U-Pb chronologic study of12test points of zircons from ametallogenic dioritic sample that connected with metallogenic process obtained a weightedaverage206Pb／238U age of （219.1±2.1）Ma (MSWD=1.8).Show the metallogenic dioriticdiagenetic era was in middle-late Triassic Indonisian movement period.Its diagenetic andmetallogenic strage were consistent with the regional tectonic-magmatic-mineralized thermalevents.combined with regional geologcal background,analysis the output background ofmetallogenic granite,There is a characteristics of mantle source type I output of granite ofmetallogenic diorite.Formed by the tectonic environment should be collision orogenicperiod,squash to stretch tectonic regime transformation.According to analysting, daxia output skarn type gold mine and hydrothermal vein typegold mine tectonic and magma activities background were same,formed in the late indosinianorogenic environment after collision,but belong to different stage and positions mineralitionproductions,daxia deposit is a compound deposit tells contact zone skarn type deposit as themain body with ore-forming mother rock mass fracture areas associated with associatedhydrothermal vein type deposit.Through reseaching on ore deposit type,ore-controlling factors, metallogenic regularityand model,ore alteration characteristics,ore-prospecting criteria and deep peripheryprospecting direction,put forward the proposal that the main prospecting direction were insiderock mass and its surrounding rock contact zone,provided the direction and technical basis formine tunnel,borehole layout,maded prospecting breakthrough and saved the prospecting cost.