松辽盆地白垩系泉头组碎屑沉积岩Nd、Pb同位素组成及成岩物质来源初步探讨

Nd-Pb Isotope Geochemical Characteristics and Discussion on the Source of the Cretaceous Quantou Group Clastic Sedimentary Rocks in the Songliao Basin

本文研究了松辽盆地庆安地区盖层白垩系泉头组碎屑沉积岩以及相关基底花岗岩的Nd、Pb同位素组成。结果表明,白垩系泉头组碎屑沉积岩和花岗岩都为地壳物质产物,其物质来源以先存陆壳的再循环物质为主,并且碎屑沉积岩和粗粒黑云母花岗岩和粗粒似斑状二长花岗岩的物质来源主要为上地壳,而细粒碱长花岗岩主要为下地壳;Pb同位素组成表明碎屑沉积岩和粗粒黑云母花岗岩和粗粒似斑状二长花岗岩属于同源产物,细粒碱长花岗岩则不同于前两者。通过对比Nd同位素组成,表明松辽盆地庆安地区的物质环境和物源与华北地块相近,而不同于华南地块,似应归于华北地块范畴。

The Nd-Pb isotope composition and source materials of the Cretaceous Quantou Group elastic sedimentary rocks and meta-granite in the Qing^an area,the Songliao Basin, are studied in this paper. The results suggest that the Cretaceous Quantou Group elastic sedimentary rocks and meta-granite are the product of elastic substances and their source materials consist of reeireulated substance of the old crust. The source materials of the clastic sedimentary rocks and coarse-grained granite were derived mainly from the upper crust, while the fine-grained granite came primarily from the lower crust. The Pb isotope composition suggests that the clastic sedimentary rocks and coarse-grained granite are cognate products, but the fine-grained granite is different from either of them. The Nd isotope composition suggests that the physical circumstance and source materials of the Qing＇an area are similar to those of the North China block, but different from those of the South China block.