Study On Geological Features And Genetic Of Zhalaxiageyong Cu-Pb-Zn Deposit In The Tuotuohe Area,Qinghai

The Zhalaxiageyong Cu-Pb-Zn deposit is discovered in 2012 by the Fifth Institute of Geological and Mineral Survey of Qinghai with the lead and copper resources of 39246.84 and 180.10 tons and has the tremendous exploration potential.Low degrees of research on the deposit and the local geological survey hamper further prospecting potential.Further comprehensive studies are urgent at present and these studies can provide references for the ore-prospecting breakthroughs in the Tuotuohe area.Detailed field investigation and abundant information collection of the geologic backgrounds were conducted.Combined with mining area and deposit geologic characteristics,as well as research on fluids inclusions and isotopic geochemistry within the deposit,we can clarify compositions and evolution process of the ore forming fluid,and ensure genesis of the Zhalaxiageyong deposit.The ore bodies of the Zhalaxiageyong deposit are mainly occurred in the rock body composed of masanophyre,and a few ore bodies are within the feldspar-quartz sandstone.The masanophyre provide the material and heat sources for the mineralization.The ore bodies are mainly hosted within two fracture zones of NWW and NNW trends,and are spread as veins and lenses.The masanophyre in the area is formed in the post-orogenic extension environment of Eocene time.The Zhalaxiageyong deposit begin to formed soon after the formation of the masanophyre.Thus closely relationships exist between the formation of the Zhalaxiageyong deposit and the emplacement of the masanophyre.The ore minerals of the Zhalaxiageyong deposit are mainly composed of pyrite,chalcopyrite,gelenite,limonite and marcasite.The gangue minerals mainly include quartz,calcite and minor sericite.The ores show idiomorphic-hypidiomorphic granular texture,allotriomorphic granular texture,poikilitic texture and cataclasitic texture,and show massive structure,brecciated structure,vein and net vein structure,disseminated structure and banded structure.The wall rock alteration includes carbonation,silication,kaolinization,ferritization,pelitization.Realagrization,orpimentation and can be also found.Mineralizing process of the Zhalaxiageyong deposit can be divided into three stages.The pyrite-quartz stage: sericitization,pyritization and silication are mainly developed in this stage.Homogenization temperatures of fluid inclusions are between 287.7~354.6? and are concentrate on 340~345?,with average value of 327.9?.The salinities are between 16.4~20.2% with mean value of 18.7%.The chalcopyrite-sericite-gelenite stage: this stage is major stage of mineralization of Pb-Zn deposit,and the ore minerals are mainly composed of chalcopyrite,gelenite and blende.Homogenization temperatures of fluid inclusions of this stage are between 202.2~307.4? and are concentrate on 225~250?,with average value of 250.7?.The main fluid inclusion homogenization temperatures in this stage can be used to represent mineralization temperatures.The depth of mineralization is estimated to be 2.88 km.Chlorite-carbonate stage: the stage is within the late-stage mineralization which is marked by the occurrence of carbonate and gypsum.Homogenization temperatures of fluid inclusions are between 140.8~220.4? and are concentrate on 165~170?,with average value of 171.2?.Depressed homogenization temperatures caused by addition of meteoric waters lead to the less precipitation of carbonate and gypsum.Zircon U-Pb ages indicate that the Zhalaxiageyong masanophyre are formed in the 32.24±0.53 Ma.The mineralization of the Cu-Zn deposit is closely related but slightly late than the emplacement of the masanophyre body.We infer that the mineralization age of the Zhalaxiageyong Cu-Zn deposit is formed between the Eocene and Oligocene.Thus,we conclude that the Zhalaxiageyong Cu-Zn deposit are belong to porphyry-type deposit,and its formation is closely related to the Eocene masanophyre body in origin.The formation age of the porphyry-type deposit is close to that of the porphyry massif and is between the late Eocene to the early Oligocene.