松树沟超镁铁岩一铬铁岩的稀土地球化学

根据岩石类型和地质产状,本文提供的稀土元素地球化学样品可分三组。通过(Ce)_N(Yb)_N变异图解和定量模式约束,第一组属轻稀土亏损型配分型式,在同源地幔条件下可形成一个密切相关的残余地幔岩组。与第二组和第三组所代表的两次岩浆事件相互印证。根据实验和定量模式计算,笔者提出底辟上涌地幔两期熔融。并运用稀土元素资料,建立了岩石成因的若干判别准则。

ON REE GEOCHEMISTRY OF SONGSHUGOU ULTRAMAFITE AND CHROMITITE

According to the types of rocks and the geological occurence the REE geochemical samples shown in this paper can be divided into three groups, the dunitic mylonite-metaperidotite-Chromitite group, the inequi-granular metadunite-chromitite group,and the diopsidite-diopside peridotite group.Through the geochemical control of the ( ce ) vs. ( yb ) variational diagram and the REE quantitative models it is shown that the first group of the samples belongs to the REE depletion model and it can form a closely related residual group under the consanguineous mantle conditions. But they don't represent a series of gradually advancing samples obtained through an unicycle process.The upper-mantle evolution in the East Qinling area may be related with the depletions or meltings of the multiprocess, which is confirmed because of the magmatic events of the second and the third samples.According to the results of the pyrolite melting experiments and the model calculations, the Writers put forward the order bistage meltings, the olivine-tholitic magma and the ultramafic magma. Briefly speaking, the So-ngshugou's ultramafites and chromitites can be divided into more than two genetic types: the magmatic cumulate and the mantle residue.The writers have set up some discriminatory standards of the two genetic types on the basis of the REE data.