汉诺坝玄武岩中地幔岩捕掳体REE和Sr,Nd同位素地球化学

本文报道汉诺坝玄武岩中地幔岩捕掳体的ＲＥＥ丰度和Ｓｒ、Ｎｄ同位素组成。不同岩石类型的ＲＥＥ配分模式和同位素组成反映地幔部分熔融程度和交代作用过程。二辉橄榄岩亏损轻稀土，是原始地幔经不同程度部分熔融的残留体。方辉橄榄岩具Ｕ型ＲＥＥ配分模式，是强烈亏损的地幔岩被熔体非化学平衡交代的结果。二辉岩脉状体富轻、中稀土，它同与脉状体接触的二辉橄榄岩可达化学平衡或近于化学平衡，而二辉岩脉状体的形成与玄武岩岩浆无成因关系。据对二辉岩脉状体和不含脉状体橄榄岩的Ｓｍ－Ｎｄ同位素定年，这种脉状体形成于３００Ｍａ左右。

REE and Sr and Nd Isotope Geochemistry of Mantle Xenoliths from Basalts in Hannuoba

REE abundances and Sr and Nd isotopic composition in mantle xenoliths from basalts in Hannuoba are reported in this paper. REE distribution patterns and isotopic compositions of different types ofrocks can reflect degrees of partial melting and metasomatic processes in the mantle. Lherzolite depleted LREE is a relict of original mantle rocks at different degrees of partial melting;harzbugite with U-typed REE distribution patterns is a product of highly depleted pyrolite which has been metasomatized by melt in chemical disequilibrium. Websterite vein and neighbouring lherzolite enriched in LREE and MREE are in chemical equilibrium or almost chemical equilibrium, but lherzolite vein might not be related to this basaltic magma. Sm-Nd isotopic geochronology of websterite vein and vein-free lherzolite indicates that vein might be formed at about 0. 3 Ga.