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1、2007年12月矿床地质第26卷第6期Dec.,2007MINERALDEPOSITSVol.26No.6文章编号:025827106(2007)0620609212X内蒙古小东沟斑岩钼矿床地质特征及成因探讨聂凤军,张万益,江思宏,刘妍(中国地质科学院矿产资源研究所,北京100037)摘要小东沟早白垩世斑状黑云母花岗岩株侵位于上二叠统火山2沉积岩中,属富碱钙2碱性火成岩。钼矿化大多产在该岩株的顶部及其内、外接触带,呈细脉浸染状、条带状和团块状,最大矿化深度可达300m。钼矿石中的金属矿物有黄铁矿、辉钼矿、黄铜矿、闪锌矿和磁
2、铁矿;非金属矿物有钾长石、石英和绢云母。从岩株中心向外,热液蚀变类型依次为硅化、钾化、云英岩化和青磐岩化,其中硅化和云英岩化与钼矿化具密切空间分布关系。据流体包裹体测试数据,可推测该矿床的形成温度为320～420℃,形成深度为1156～2185km。稳定同位素测定结果表明,钼矿石主要是以岩浆水为主的混源流体淀积的结果,硫和钼主要来自中酸性岩浆源。另外,低f(O2)和高f(S2)的弱酸性还原效应以及成矿流体“沸腾”作用均是导致辉钼矿沉淀的原因。小东沟矿床属斑岩型中高温热液钼矿床。关键词:地质学;斑岩钼矿床;地质特征;成矿作用
3、;成矿流体;小东沟;内蒙古中图分类号:P618.65文献标识码: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
