山西代县金红石矿床洪塘矿区含矿岩石的地球化学及年代学  

Geochemistry and chronology of Hongtang ore-bearing rocks in the Daixian rutile deposit,Shanxi Province

作　　者：庞尔成 徐永婧[1,2] 施光海[2] 贾琇明[3] 张尊侠 

机构地区：[1]山西省地勘局二一七地质队,山西大同037008 [2]中国地质大学,北京100083 [3]太原理工大学,山西太原030024 [4]青海省有色地勘局矿勘院,青海西宁810007

出　　处：《岩石矿物学杂志》2010年第5期497-506,共10页Acta Petrologica et Mineralogica

基　　金：山西省国土资源厅"山西省代县羊延寺金红石矿普查"项目资助

摘　　要：山西代县洪塘金红石矿区是代县金红石矿3个主要矿区之一,含金红石矿的岩石主要有4种类型:直闪石片岩和蛭石化阳起-直闪石片岩、钠长斜绿泥石阳起-直闪石片岩和蛭石化阳起-直闪石英岩。除1个样品已硅化(HT-5,石英岩)外,SiO2含量为47.83%～55.03%,富MgO、TiO2和Al2O3,低CaO、Na2O和K2O,轻稀土元素略亏损,重稀土元素分布较平坦,具明显负Eu异常,大离子亲石元素含量变化较大,高场强元素总体上没有明显分异,Ti、Zr、Hf和Y轻微亏损,Ba、Sr和Rb亏损。据以上地球化学特征推测其原岩化学组成等同于基性岩浆岩类中的洋中脊拉斑玄武岩类,后经过变质作用形成上述含矿岩石。含矿岩石中锆石的内外部生长特征、矿物包裹体特征以及U-Pb年龄结果显示,该区含矿原岩——中基性玄武质岩浆岩的成岩时代为2530Ma左右,后可能经历了2530～2370Ma和1900Ma左右的热液流体活动参与的高角闪岩相到绿片岩相的区域变质事件。The Daixian rutile deposit is located in western Hengshan and belongs geotectonically to the central zone of North China Craton.The exposed strata mainly comprise a suite of medium-grade regional metamorphic rocks of Upper Archaean Wutai Group.The rocks have undergone multi-stage amphibolite facies metamorphism and deformation.Recent exploration shows that the Daixian rutile deposit is one of the largest rutile deposits in China with reserves up to 3.7 million tons of TiO2.The Hongtang rutile orefield is one of the three main orefields in the Daixian rutile deposit.The rutile-bearing rocks mainly include anthophyllite schist,vermiculitized antinolite schist,albite-clinochlore-bearing antinolite schist and vermiculitized actinolite-bearing quartzite.Except for one silicified sample （HT-5,quartzite）,they contain 47.83%～55.03% SiO2,high MgO,TiO2 and Al2O3,low CaO,Na2O and K2O,and are depleted in LREE and roughly flat in HREE and have conspicuous negative Eu anomalies.LILE content changes slightly,and differentiation of HFSE is inconspicuous.The rocks are slightly poor in Ti,Zr,Hf,Y,and Ba,Sr,Rb.The samples with high Ti （TiO24%） have conspicu-ous positive Nb and Ta anomalies.The authors thus infer that the protolith of the rutile deposit is chemically equivalent to mid-ocean ridge tholeiite,and that the ore-bearing rocks were formed through crystallization differentiation of anorthite and other types of metamorphism and deformation.The growth characteristics and mineral inclusions of zircons in the ore-bearing rocks as well as U-Th-Pb ages show that the protolith of the Hongtang rutile orefield was formed around 2 530 Ma and might have experienced two regional metamorphic events with hydrothermal fluid mixture during 2 370～2 530 Ma and around 1 900 Ma,corresponding respectively to high grade amphibolite facies and medium-pressure and low-temperature greenschist facies.

关 键 词：锆石年代学 直闪石片岩 金红石矿床 山西代县 

分 类 号：P597.3[天文地球—地球化学] P588.12[天文地球—地质学]