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1、2007年12月礦床地質(zhì)第26卷第6期Dec.,2007MINERALDEPOSITSVol.26No.6文章編號:025827106(2007)0620609212X內(nèi)蒙古小東溝斑巖鉬礦床地質(zhì)特征及成因探討聶鳳軍,張萬益,江思宏,劉妍(中國地質(zhì)科學(xué)院礦產(chǎn)資源研究所,北京100037)摘要小東溝早白堊世斑狀黑云母花崗巖株侵位于上二疊統(tǒng)火山2沉積巖中,屬富堿鈣2堿性火成巖。鉬礦化大多產(chǎn)在該巖株的頂部及其內(nèi)、外接觸帶,呈細脈浸染狀、條帶狀和團塊狀,最大礦化深度可達300m。鉬礦石中的金屬礦物有黃鐵礦、輝鉬礦、黃銅礦、閃鋅礦和磁
2、鐵礦;非金屬礦物有鉀長石、石英和絹云母。從巖株中心向外,熱液蝕變類型依次為硅化、鉀化、云英巖化和青磐巖化,其中硅化和云英巖化與鉬礦化具密切空間分布關(guān)系。據(jù)流體包裹體測試數(shù)據(jù),可推測該礦床的形成溫度為320～420℃,形成深度為1156～2185km。穩(wěn)定同位素測定結(jié)果表明,鉬礦石主要是以巖漿水為主的混源流體淀積的結(jié)果,硫和鉬主要來自中酸性巖漿源。另外,低f(O2)和高f(S2)的弱酸性還原效應(yīng)以及成礦流體“沸騰”作用均是導(dǎo)致輝鉬礦沉淀的原因。小東溝礦床屬斑巖型中高溫?zé)嵋恒f礦床。關(guān)鍵詞:地質(zhì)學(xué);斑巖鉬礦床;地質(zhì)特征;成礦作用
3、;成礦流體;小東溝;內(nèi)蒙古中圖分類號:P618.65文獻標(biāo)識碼:AGeologicalfeaturesandoriginofXiaodonggouporphyrymolybdenumdepositinHexigtenBanner,InnerMongoliaNIEFengJun,ZHANGWanYi,JIANGSiHongandLIUYan(InstituteofMineralResources,CAGS,Beijing100037,China)AbstractLocatedintheeasternmostpartofthe
4、EarlyPaleozoictectono2magmaticbeltwithintheOndurSum2Ongni2udBanneronthenorthernedgeoftheNorthChinaCraton,thenewlydiscoveredXiaodonggoudepositisamedi2um2sizeporphyrymolybdenumdepositoccurringincentral2easternInnerMongolia.DuringtheMesozoicYan2shanianorogeny,intense
5、tectonicandigneousactivitiesresultedinlarge2scalegranitoidmagmatisminXiaodong2gouanditsneighboringareas.TheXiaodonggougranitoidporphyrystockwasemplacedinthevolcano2sedimen2tarysequenceoftheUpperPermianRanfangdiFormation,controlledbytheNS2trendingfaultzone.Withan2o
6、utcropareaof0122km,itconsistsmainlyofporphyriticbiotitegraniteandfine2grainedbiotitegranitewhichhavethesamemineralassemblage.Rock2formingmineralsaremainlyquartz,microcline,microperthiteandpla2gioclaseassociatedwithminorbiotiteandsericite.Accessorymineralscomprisem
7、agnetite,apatite,zircon,spheneandallanite.TheporphyrystockispetrochemicallycharacterizedbyrelativelyhighSiO2,K2O,Rb,UandTh,andobviouslylowCaO,Fe2O3+FeO,MgO,Sr,Ba,Nb,TaandREE,thusbelongingtosilicon2high,potassium2richrockofcalc2alkalineseries.Molybdenummineralizati
8、onoccursexclusivelywithintheXiaodonggouporphyriticgranitoidstockasveins,veinletsanddisseminatedblocks.Molybdenumoreconsistsofpyrite,chalcopyrite,molybde
