华南古生代花岗岩类Nd-Sr同位素研究及华南基底

STUDY OF SOURCES OF PALEOZOIC GRANITOIDS AND THE BASEMENT OF SOUTH CHINA BY MEANS OF Nd-Sr ISOTOPE

统计表明,华南古生代花岗岩类的形成,主要集中在两个时期:奥陶纪到泥盆纪和二叠纪到三叠纪。 Nd-Sr同位素结果表明,这两个时期花岗岩类,主要来自地块深部古老大陆基底。这一基底的最老年龄,大约为20亿年。根据全球花岗岩类ε_(Nd)(0)随岩体形成时代演变统计规律,推算表明,确实存在有一种类型花岗岩类,其形成和地幔密切相关,还极有可能就是地幔派生的产物。

The classification of ages shows that two periods from Ordovician to Devonian and from Permian to Triassic were significant for the granitoids of South China (Fig.2). The Nd-Sr isotopes of Paleozoic granitoids from South China reveals that sources of the granitoids were likely the old basement of terrain (Fig.3). And according to the trend of evolution of E_(Nd)(0) of granitoids with era, it was suggested that the ages of the old basement of terrain be 1.5--20 Ga(Fig. 4). The algebraic deductions based on the correlation between E_(Nd)(0) of granitoids and era suggest that there is a kind of granitoids the genesis of which was closely related to the mantle, and that the deriving of granitoids from mantle (Fig, 5) happend continually in the history of the Earth(Fig. 4).