女山单斜辉石巨晶锂同位素组成的离子探针分析  

LITHIUM ISOTOPIC COMPOSITION OF CLINOPYROXENE MEGACRYSTS FROM NüSHAN, EASTERN CHINA: AN ION PROBE ANALYSIS

作　　者：杨晓志[1] 夏群科[1] E.Deloule 

机构地区：[1]中国科学技术大学地球与空间科学学院化学地球动力学研究实验室,安徽合肥230026 [2]法国国家科研中心岩石学和地球化学研究中心

出　　处：《矿物学报》2003年第4期359-363,共5页Acta Mineralogica Sinica

基　　金：国家自然科学基金(49803002)

摘　　要：应用离子探针技术测定了一组女山单斜辉石巨晶的锂同位素组成。结果表明,无论是不同样品之间还是同一样品内部,锂同位素组成都是均一的,δ7Li=(+8.0±2.7)‰,明显高于MORB值(+1.5‰～+5.1‰)。巨晶的锂同位素组成直接继承自地幔源区,高δ7Li的特征暗示源区受到过俯冲海洋板块析出流体的交代作用。结合Sr Nd同位素的资料来看,交代流体可能来自于蚀变洋壳而不是海洋沉积物。Lithium isotopic composition of clinopyroxene megacrysts from Nüshan has been analyzed by means of ion probe. The result indicates that both within the same grain and among different grains, lithium isotopic ratios are homogeneous:δ~7Li=(+8.0±2.7)‰, apparently higher than the 'normal mantle' values (+1.5‰～+5.1‰). Lithium isotopic composition of the megacrysts has been inherited from the deep source, and the high δ~7Li suggests that the mantle source was influenced by fluids from the subducted oceanic plate. Combining with the Sr-Nd isotope data, the fluids are inferred to have stemmed from altered ocean crust other than sediments.

关 键 词：单斜辉石巨晶 锂 同位素 离子探针 

分 类 号：P597.2[天文地球—地球化学] P588.145[天文地球—地质学]