中国东部上地幔岩石组构与稀土配分之间的关系

RELATIONSHIP BETWEEN FABRIC CHARACTERISTIC OF UPPER MANTLE ROCK AND ITS REE PARTITION ING MODEL IN EAST CHINA

本文通过对中国东部新生代玄武岩中二辉橄榄岩包体的研究认为,上地幔岩石变形结构和组构类型在不同大地构造单元中的分布是不同的,据此,可划分为华北—东北上地幔弱变形域和东南沿海上地幔强变形域。与变形特征对应的东南沿海地区包体稀土元素配分型式为LREE富集型,华北—东北地区包体稀土元素配分型式则为平坦型和轻微LREE富集型,这表明上地幔流变剪切作用强度与稀土元素富集作用呈正相关,同时反映出上地幔流变状态的差异。根据包体变形特征,我们提出华北—东北地区与东南沿海地区中新生代具有截然不同的大地构造演化特征。

The study of lherzolite xenoliths in cenozoic basaltic rocks in east China shows that the distribution types of deformation texture and fabric of upper mantle are different in different geotectonic unit. Accordingly , the eastern China is divided into Huabei-Dongbei weak deformation domain and Dongnanyanhai strong deformation domain. Corresponding to the characteristic of deformation, REE partitioning model of xenoliths in Dongnanyanhai is LREE enrichment model, but REE partitioning model of xenoliths in Huabei-Dongbei is LREE slight enrichment or flat model. This indicates that it has the characteristic of positive correlation between shearing intensity of upper mantle rheology and REE enriching. Moreover , it shows the different of rheology state of upper mantle in different unit and depth. Finally , according to the characteristic of deformation and metamorphosis of xenoliths, the author suggestes that Huabei-Dongbei and Dongnanyanhai region in Mesozoic-Cenozoic are in distinct different characteristic of geotectonic evolution.