新疆北部花岗岩类的稀土特征

新疆北部的改造系列花岗岩演化由斜长花岗岩阶段、钾长花岗岩阶段至碱长花岗岩阶段,其稀土配分组成递降曲线簇.新疆北部的同熔型花岗岩类稀土配分基本为轻稀土富集型,具Eu负异常,有递增曲线簇和递降曲线簇两种情况.深源碱性系列轻重稀土比值大、Eu负异常一般不显著.文中还叙述了新疆北部的幔分异系列花岗岩类及一些古老花岗岩的稀土特征.

REE CHARACTERISTIC OF GRANITOID IN NORTHERN XINJIANG

The evolution of transformed series granitoid in northern Xinjiang can be divided into three stages. The first stage: plagiogranite stage is characterized mainly by autochthonous anatexis-metasomatism with a little allochthonous intrusion. The REE distribution curves basically correspond to those of the source rock, which suggests that they are results of anatexis of crust rock. The second stages adamellite-potash feldspar granite stage is characterized by developement of meta-somatic type and allochthonous intrusive type. The total amount decreases for REE greatly for HREE, and sharply for Eu, but the La/Yb ratio increases. The last stage is characterized by further decrease of total REE of intrusive muscovite alkali-feldspar granite and great decrease of LREE with standardized curves approximating to horizon and Eu trough deepening. The main REE partition pattern of syntectic series granites in northern Xinjiang is B-type of Wang Zhonggang. Their standardized curves include progressively increased curves and progressively decreased curves which are associated with the degree of crystallization, metasomalism and assimilation et al. A great La/Yb ratio existing in deep-source alkaline series granites suggests a deeper source of granites. At last stage the total REE increases and the Eu trough deepens. The Precambrian granites of Kuluktag with a big La/Yb ratio, a small amount of REE and Eu 1.0, which suggest anatexis of Archean of lower Proterozoic rock, are similar to those of other regions in the world. This paper also describes REE characteristic of mantle-source granites of