【摘要】 在四个地幔端员(DMM、HIMU、EM1、EM2)中,EM1的成因一直令人困惑。华北克拉通中部(太行山地区)地幔橄榄岩捕虏体的Li同位素组成特征为探讨这一问题提供了新的制约。橄榄岩捕虏体中主要组成矿物(橄榄石、斜方辉石和单斜辉石)的Li同位素组成特征表明,该区的岩石圈地幔中有再循环的、古老的洋壳物质。结合已有的地幔橄榄岩捕虏体的Sr-Nd同位素数据,可以推测再循环的古老蚀变洋壳对地幔EM1端员组分的产生有重要的作用。更多还原

【Abstract】 The origin of the EM1 end-member in the mantle is a long-standing geochemical puzzle among the four typical mantle end-members(DMM,HIMU,EM1 and EM2).The characteristics of Strontium(Sr),Neodymium(Nd) and Lithium(Li) isotopic compositions in the mantle peridotite xenoliths hosted in the Cenozoic basalts from Hannuoba,Yangyuan,Fanshi and Hebi localities in the Central Zone of the North China Craton,one of the oldest continents in the world,provide new constraints on this issue.Extreme fractionation of Li isotopes and isotopically very light Li in the constituent minerals(olivine,orthopyroxene and clinopyroxene) of the peridotite xenoliths indicates that recycled ancient oceanic crust is existent in the subcontinental lithospheric mantle beneath the North China Craton.Comparison of these data with existing Sr and Nd isotopic ratios of peridotite xenoliths from this region reflects that the recycling of ancient oceanic crust by subduction,storage in the mantle,and reappearance in volcanism via mantle circulation,may play an important role in generating the EM1-type mantle end-member.更多还原