华南花岗岩物源成因特征与陆壳演化

EVOLUTION OF CONTINENTAL CRUST AND MATERIAL SOURCE (GENESIS) OF GRANITOIDS IN S.CHINA

华南不同时代的花岗岩按物质来源及成因可划分为:幔源(分异)系列:幔-壳混源(同熔)系列;壳源改造(重熔)系列和幔-壳混源碱性系列等四个不同的系列,简要阐述了划分四类系列的岩石学、地球化学的依据。侧重根据Sm-Nd、Rb-Sr同位素成分,以二元混合模型计算了花岗岩源区物质组成中,上壳和亏损地幔组份各占的比例。在此基础上探讨了不同物源成因系列花岗岩形成与华南陆壳演化的内在联系:东安、雪峰旋回褶皱系阶段花岗岩物源成因类型比较多样,有幔源(分异)系列、不成熟壳源、成熟壳源改造(重熔)系列等;加里东,海西期以陆壳改造(重熔)系列为主;印支、燕山期活化区(地洼)阶段,在地幔活化激发下,中国东部陆缘形成幔—壳混源(同熔)系列花岗岩和相应的火山岩;但沿内部断裂带,在壳下地幔热传输及构造作用下引起陆壳重熔,形成属于壳源改造(重熔)系列花岗岩。同位素的研究证明了:地洼阶段的构造-岩浆活动主要动力是来自壳下地幔的活化。

According to material source and genesis, the authors divide the granitoids in S. China into four series:mantle-derived (differentiation); mantle plus crust mixed source(syntexis); crust derived transformation (remelting);and mantle plus crust mixed source (syntexis) alkaline. The most important characteristics of different series of granitoids have been discussed in this paper. Mainly based on Sm-Nd, Rb-Sr isotopic compositions of granitoids of different ages, and using binary mixed model,the authors have calculated the proportions of upper crust and depleted mantle end members within source rocks of granitoids and discussed the interrelationship of granitoid generation and continental crust evolution:during the Donganian and Xuefengian cycles,the granitoids show diversity in material source and genesis series, including mantle derived series and unmatured or matured continental crust-derived transformation series etc.: during the Caledonian and Hercynian cycles, the granitoids were mainly of continental crust-derived transformation series. In the Indosinian-Yanshanian activated region cycle, as a result of mantle activation,the syntexis series granitoids and related volcanic rocks of mantle plus crust mixed source have been formed, stretching along the east coast of China. Inversely,continental crust transformation series granitoids of this period are restricted at the continental margin.The Sm-Nd,Rb-Sr isotopic investigations of granitoids have comfirmed that the mantle activation is the main driving force for the tectono-magmatic evolution in the diwa stage.