长江流域岩体的时空分布与碎屑锆石物源示踪

Rock Types in Yangtze Drainage and Their Implications for Zircon UPb Provenance Study of Yangtze Sediments

摘要:

结合区域大地构造演化,系统总结并讨论了长江流域火成岩的时空分布特征及其对长江中下游沉积物物源的指示意义.结果表明,长江流域岩体的时空分布特征与区域构造演化密切相关; 青藏高原新生代酸性侵入岩和火山岩以及云贵川高原晚二叠世峨眉山玄武岩及伴生酸性岩是长江上游地区的特征岩体; 汉江和湘江—赣江流域早古生代中酸性侵入岩是长江中游地区的特征岩体; 白垩纪中酸性侵入岩和火山岩是长江下游地区的特征岩体.这一成果可直接用于指导长江中下游地区利用碎屑锆石UPb年代学和Hf同位素进行物源示踪的工作.在钻孔沉积物中准确识别出这些特征年龄信息,并结合沉积物古地磁年代的标定对研究长江的地质演化历史具有重要指示意义.

Abstract:

The igneous rocks of each subplates in the Yangtze drainage were discussed on the basis of their tectonic settings in order to provide fingerprints for the riverine sediments in the lower valley.Results indicate that the distribution of rock types is closely related to the evolution of tectonics in the Yangtze drainage.The Cenozoic felsic rocks in the Tibet Plateau and the late Permian basalts and concomitant felsic rocks of the Emeishan large igneous province in the adjacent area around Sichuan,Yunnan and Guizhou province are typical rock bodies in the upper Yangtze drainage.Early Paleozoic felsic rocks outcrop primarily in the Cathaysian Bock and Qinling Mountain,which are typical rock bodies in the middle reaches.Cretaceous felsic magmatic and volcanic rocks occurring mainly in volcanic basins along Yangtze River are dominant in the lower Yangtze basin.The recognition of the distribution of main igneous rock bodies in the whole Yangtze drainage basin will be of great help for sediment provenance study of the Yangtze River based on the methods in combination with detrital zircon UPb dating and Hf isotope analysis,which may result in uncovering of the evolution history of the Yangtze River.