金川岩体稀土元素特征及成因意义

THE REE CHARACTERISTICS AND THE GENESIS SIGNIFICANCE OF THE JINCHYUAN ORE-BEARING ULTRABASIC INTRUSIVE GANSU PROVINCE CHINA

本文据稀土元素特征将金川含矿超基性岩体岩石和矿石类型分为:无(弱)矿化橄榄二辉岩和辉石岩、无(弱)矿化二辉橄榄岩、含海绵状矿含二辉橄榄岩、含海绵状矿纯橄榄岩以及含少量造岩矿物纯硫化物块状矿五类。稀土元素特征表明,稀土元素总量与岩石的基性程度和硫化物矿物含量呈反相关关系;铈异常的出现是由蚀变而引起,其大小与岩石蚀变程度强弱有关。通过定量模型计算,认为金川含矿超基性岩体的原生岩浆是上地幔岩经22～46％的部分熔融形成的苦橄质拉斑玄武岩浆。

The different samples of rocks and ores are selected, 14 samples of REE are introduced and the REE characteristics are basically summarized in this paper.On the basis of these, the rock and ore types are divided into 5 classes. Except for the fifth class-the pure-sulfide depleted in LREE, the others are slightly enriched in LREE. The REE patterns are nearly parallel to each other in every class. With the increase of the magmatic acid degree, the cure positions of the REE distribution of the pattern figures continue to remove upwards. The acidic rocks are more usually enriched in both LREE and REE. The REE abundances of rocks are increasing with the decrease of basic degree. It is because the REE contents and the characteristics of olivinepyroxene are different. With the increase of sulfides, REE is depleted. The reason is because sulfides have the smaller REE partition coefficient or because the silicate remants are remelted after the silicate magmas are separated during the partial melting of pyrolite. The Ce abnormal takes place because of alteration. The higher the position is, the larger the ratio of (La/Yb)N, (Ce/Yb>N. is.According to the calculation of the REE quantitative models, it is found that the primary magma of the Jinchuan intrusive was tholeiite magma in which pyrolite had undergone 22-46% partial melting.