云南双沟变质橄榄岩中蛇纹石的稀土元素空间分布

本文探讨变质橄榄岩的ＬＲＥＥ富集型及Ｕ型分布的ＲＥＥ球粒陨石模型，是橄榄石固有的还是后期蚀变形成的。并寻求复原蚀变前橄榄石的ＲＥＥ丰度及型式。我们用蛇纹石颗粒代表蚀变后的橄榄石，用分选法和化学分层剥离法对样品进行予处理。用中子活化分析（ＮＡＡ）手段进行了测试。结果表明：分选法确定了ＬＲＥＥ的主要赋存载体是蛇纹石。分层剥离最后内核的ＲＥＥ丰度及模型，可近似地作为原来（未蚀变前）橄榄石的ＲＥＥ丰度及模型。

Preliminary Study on the Spatial Distributionin of Rare-Earth Element in Serpentines

The normalized chondrite REE patterns of metamorphic peridotites occured in the Shuanggou ophiolite from Xinpin County, Yunnan Province, are almost LREE-enriched. In comparison. the REE patterns of primary partial melting of mantle are LREE-depleted. LREE-depleted primary melt can not be melt out from LREE-enriched mantle. This may be that the mantle is altered and replaced by the hydrothemal liquid carrying LREE and LILE. To prove this inference, an experiment of strip layer by layer was made and the REE distributions of district layered serpentines are measured with RNAA. The experiment exibits that the REE distributions are different from surface to the core in each layer of serpentines, and their REE patterns are also varied from LREE-enriched gradually to LREE-depleted. These distrubution curves of LREE are much different whereas those of HREE are most alike and parallel. This kind of distribution is not likely to be formed by crystallization of olivine. The only possibility is a result of later alteration and replacement.