Study On The Metallogenic Series Of Cobalt Deposits In Eastern Kunlun Orogenic Belt

Cobalt discovered newly is an important mineral species in Eastern Kunlun Orogenic Beltand has shown favorable prospecting prospects, high tenor and large scale reserves. Nowadays,three cobalt deposits have discovered, that is, Kendekeke and its periphery cobalt-bismuth-golddeposit, Tuolugou cobalt-gold deposit and Dulenggou copper-cobalt deposit. There are associatedcobalt deposit and independent cobalt deposit in this orogenic belt. What are the ore-controllingcharacteristics and how about their ore-forming metallogenic dynamic mechanism and geology ofmineral deposit? The dissertation discussed these scientific problems detailedly.Eastern Kunlun Orogenic Belt, western part of China's central orogen, is located in thesouthern margin of Qaidam massif. The belt has undergone polycyclic complex orogenicprocesses, polycyclic ocean-continent transition and complex intercontinental evolution after thecollision. As a result, typical structure-magma-sedimentation was formed. From north to south,Eastern Kunlun orogenic belt can be divided into Kunbei back-arc basin, Kunzhong basementuplift and granitic belt and Kunnan composite belt. Outcropped stratums regionally have thecharacteristics of great era span and distinct difference. The predominant stratums include thePrecambrian, Ordovician of early Paleozoic, Carboniferous-Permian of late Paleozoic and Triassicof Mesozoic. Eastern Kunlun orogenic belt have formed E-W fractured zone since the Paleozoicbecause of the influence of three regional faults. Extensive magmatism was developed anddifferent epoch rock assemblage demonstrated the plate subduction-collision and evolution ofpolycyclic ocean.Volcanics rocks of Eastern Kunlun orogenic belt can be divided into four series: pre-Xingkai,Caledonian, Variscan and Indosinian-Yanshanian. Pre-Xinkai volcanic rocks are composed ofbasaltic lava of Wanbaogou group. Chemical components of volcanic rocks wholly belonged tosubalkalic series. Characteristics of geochemistry and sedimentation formation indicated that theforming environment was oceanic volcanic island. Caledonian volcanic rocks included Nachitaigroup and Tanjianshan group. Furthermore, volcanic rocks of Tanjianshan group are bimodalvolcanic rocks composed of basic basalts and intermediate-acidic basalts. Geochemistry showedthe Tanjianshan group is developed in back-arc basin tectonic environment. Nachitai group mixedsome limestone and siliceous rocks formed in turbid deep water. Variscan volcanic rocks arecomposed of Maoniushan group, Dagangou group, Halaguole group and Haoteluowa group.Calcalkalic volcanic rocks of early Carboniferous Halaguole group are the magmatic islandvolcanic rocks developed in island arc of active continental margin volcanic rocks. Halaguolegroup of Kunnan composite belt develop tholeiitic basalt series and Calcalkalic seriescharacterized by magmatic arc showing its formation have genetic relation with the northwardsubduction of Bayan Har ocean.Metamorphisms make the mineral elements redistribution and enrichment in Eastern Kunlunorogenic belt. For metamorphisms, the great contribution to mineral deposit is that they can supplymetamorphic fluids, remobilize the mineral elements and extract the mineral elements from sourcebeds.Regional gravity and aeromagnetic anomaly present the N-W orientation in the Western partE-W orientation in Middle part and N-E orientation in Eastern part. Gravity anomaly reflects E-Wand N-W orientation gradient belt and mineral resources of non-ferrous metal have closerelationship with the N-W orientation gravity and aeromagnetic anomaly. Along the gravitygradient belt and periphery of the aeromagnetic anomaly, some commercial non-ferrous metaldeposits have been discovered. Ore bodies were hosted in anomaly intersection frequently. EasternKunlun mineralized belt is located active fractured zone, lithospheric thinning and havecoincidence relation with the strong earthquake center. Mineral deposits are formed along the lowvelocity zone and the transitional belt between the high velocity zone and low velocity zone.Exhalative sedimentation formations are developed extensively in Eastern Kunlun orogenicbelt. Because of the influence of the different metallogenic geological-structural setting, somespecial submarine hydrothermal exhalation sedimentation formations were formed. For example,Kendekeke ore district located in Qimantage aulacogen developed siliceous rocks-bearing SEDEXformation. However, Tuolugou ore district located extensional oceanic setting developed siliceousalbitite-bearing volcanic clastic debris sedimentation formation. Dulenggou copper deposit isformed in subduction backgroup of Bayan Har ocean and develop Calcalkalic series magmatic arc.According to the volcanic assemblages,sedimentation formation and mineralization,EasternKunlun orogenic belt can be divided into Kunbei belt(Qimantage back arc basin) ,Kunzhongbelt(basement uplift and granitic belt) and Kunnan belt(composite belt).Geodynamic evolution in Eastern Kunlun Orogenic beltBased on the data made by former researchers and the author's investigation,the geologicalhistory of the orogen has been divided into three stages,i.e. pre-Caledonian,Caledonian andIndochinese-Himalayan.Pre-Caledonian evolution inludes formation of Precambrain platform,breakup and convergeof Proterozoic paleocontinent.Wanbaogou oceanic bassalts,which is important to understand thetectonic evolution, were formed in late Proterozoic.The ocean plate of the Proto-Tethys began to be consumed by northward subduction toQaidam massif along the location of the present Kunzhong falut in eary Paleozoic.And structuralframe of Kunbei and Kunnan was formed.With the devlopement of the subduction,trench wasappeared in the sourthern margin of Qaidam massif.Active continent margin was formed betweenthe Kunzhong fault and Kunbei fault,but a back arc basin was formed in Kunbei belt.Bimodalvolcanic rocks were distributed intensively.By that time,a trench-arc-basin system was developedin the southern edge of Qaidam massif.Nachitai group,whichi composed of volcanic clastic rocksand carbonatite formation was formed in the basalt plateau after formation of the Wanbaogouoceanic basalt and before collision with Qaidam massif.In early middle Silurian, siliceous albititewas formed in extensional tectonic setting of Wanbaogou oceanic basalt plateau. In lateCaledonian,Wanbaogou plateau basalts were collaged to the Qaidam massif.the late Paleozoic volcanic rocks were formed in continental magmatic arc and they furtherpointed out that the subduction of this stage belonged to Andes-type.The oceanic crust wasdirectly subducted downward to the continent without island arc formed.The Hercynian granites,mainly batholiths,are the most widely developed intrusives in theorogenic while early Indochinese granites are mostly stock-shaped and mainly distributed inKunnan bent.Based on petrochemical data,it is recognized that the granites of this stage belong tosubduction and syncollisional type.Since lated indochinese stage,intensive crustal-mantle reactionhappened,which lead to the formation of a series of widely distributed mafic-ultramaficintrusives.The tectonic regime transormed from compressional orogeny to extensional liospherethinning,which coincided the beginning of the breaking up of the supercontinent Pangea.Thetectonic regime transformation controlled the formation of mantle-derived,mantle-crustal bybridmagmatic activities and a large number of hydrothermal ore deposits in late Indochinese.Metallogenic Mechanism of Typical Deposit of Eastern Kunlun Orogenic Belt:Kendekeke Co,Bi and Au deposit: It developed in the early Paleozoic back-arc basin ofKunbei fractured zone. With the northward subduction of southern seamounts, back-arc basin andsubmarine hydrothermal exhalation sedimentation ore-bearing formation are formed. Submarinehydrothermal exhalation sedimentation formed siliceous rocks and particulate pyrites, pyrrhotites,gel pyrites and other Co, Bi, Au and Cu multiple ore-forming elements. Because of short life ofactive basin, thermal power is small comparatively; the hydrothermal sedimentation providedimportant ore-forming materials for the late mineralization. Hercynian orogenic activities enrichedthe mineral elements again. Large scale mineralization developed in Mesozoic era and is thepredominant mineralization stage for Kendekeke deposit. Indosinian-Yanshanian magma broughtstrong thermodynamics condition and hydrothermal replacements make the metallogenic elementsreactive, remobilized and enrich in special location. The typical hydrothermal sedimentation stagecan formed the rock, not ore deposit, and skarnalization is the predominant mineralized stage.Tuolugou Co deposit: Bayan Har Ocean located in southern part of Eastern Kunlun orogenicbelt entered the oceanic subduction phase after the Paleozoic extension. Metallic elements wereaccumulated by hydrothermal activities caused by seeping of seawater and formations bearing Coand Au were formed gradually.Modified mineralizations and deformation of fold and shear havebeen developed in Yanshanian-Himalayan thrusting.There were extensive structural deformationand replacement and no large scale magmatic intrusions in Kunnan belt similar to the paleozoicKunzhong belt.Primary stratifications were replaced by penetrative foliations.Mineralizedsiliceous albitite were defomated and reoriented and characteristics of stratiform but notbed,veinlike but not vein have been generated.Later phase structures developed intensively cut theoriginal mineralization belt and formed diverse uplift and denudation.Dulenggou copper deposit:There are three mineralizatinal ways.First Bayan Har oceansubduction along southern part of Eastern KunLun orogenic belt ,the deep penetrating and heatedsea water reacted withrocks,and Cu,Co,Fe ore-forming elements,.Second under the influence oflate (HaiXi-Indosinian)tectonic movements,,ore-forming elements suffered strong tectonicdeformation,folding, morphology of orebodies shows lensoid in space.Cobalt deposits are controlled by metallogenic dynamics.According to geotectonic setting,characteristics of ore-controlling structures and metallegenic mechanism, the cobaltmetallegenesis in Eastern Kunlun Mountain can be divided into four metallegenic series, i. e.sedimentary exhalative ( source bed ) –hydrothermal fluid superposed, sedimentary exhalative–deformation reconstruction, hydrothermal fluid and skarn metallegenic series.The Cobalt metallogenic model was built in Eastern Kunlun Mountain, it underwent thefollowing stages, i. e. the early Caledonian sedimentary exhalative stage that provided the sourceof Cobalt deposit, the late Caledonian deformation reconstruction stage that formed sedimentaryexhalative–deformation reconstruction Cobalt deposit, Hercynian-Yanshan magmatism stage thatprovided heat and ore source and formed hydrothermal vein and skarn cobalt deposits.The metallogenic potential of cobalt was discussed by us. The potential of the dominantcobalt deposit types grade in the following turn, i. e. sedimentary exhalative–deformation...