【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。更多还原

【Abstract】 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.更多还原