A PRELIMINARY STUDY ON THE REE EVOLUTION CHARACTERISTICS AND THEIR FORMATION MECHANISM OF THE GRANITOIDS IN XIANGHUALING (HSIANGHUALING) DISTRICT
香花岭地区花岗岩类岩石稀土元素演化特点及其形成机理的探讨

In the Xianghualing (Hsianghualing) district, South Hunan, there are mainly three types of granitoids, i. e, the biotitegranite, zinnwaldite-albite-granite and Hsianghuagite. These granitoid rocks are formed by the same granitic magma in different stages and constitute a complete magmatic evolutionary series.With the magma evolving, the REE contents and negative Eu anomaly decrease progressively, and the LREE are more and more enriched as compared with HREE. Abovementioned facts show an evolutionary tendency of REE of the granitoids in the study district contrary to that of the granitoids elsewhere.The components of the granitic magma system become poorer in Si,(K + Na), richer in Al, Li, F and H2O+ during the evolution, which caused weaker acidity and stronger alkalinity. It may be the most important reason for the specific REE evolution of the granitoids in this district. In addition, the varied oxidation-reduction environments in different evolutionary stages of this magmatie system may be the other reason.