长江上游表壳岩系Pb同位素组成特征及对三峡贯通的示踪意义  

Pb Isotopic Compositions of Supracrustal Rocks in the Upper Yangtze River and Its Indication to the Formation of Three Gorges

作　　者：张增杰[1] 李长安[1,2] 孙习林[1] 林旭[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]中国地质大学生物地质与环境地质国家重点实验室,武汉430074

出　　处：《地质科技情报》2014年第1期74-79,84,共7页Geological Science and Technology Information

基　　金：国家自然科学基金项目(40971008);中国地质调查局地质调查项目(1212011121142)

摘　　要：理论分析表明,碎屑钾长石Pb同位素在大河流域沉积物物源示踪及追索河流演化研究中具有独特意义。近年来,随着单颗粒碎屑矿物微区分析技术的快速发展,碎屑钾长石Pb同位素已成为一种有效的物源示踪方法,在判别沉积物物源、重建古水系等方面已得到了较好的应用,同时沉积物全岩的Pb同位素能对碎屑钾长石Pb同位素的示踪起到一定的补充作用。通过对长江流域不同河段和支流流域钾长石及全岩Pb同位素的空间分异特征的即可识别性分析、河流地貌和水文特性对源-汇之间物质的可通达性分析以及流域地质环境条件的分析,认为利用Pb同位素方法来示踪江汉盆地不同时期沉积物的源区,并重建长江水系的演化过程是可行的。最后对开展此项研究的思路进行了讨论。Theoretical analysis shows that the Pb isotopic composition of detrital K-feldspar has a unique significance in tracing evolution of the large-scale drainage. In recent years, with the rapid development of the single-grain detrital mineral in-situ-analytical techniques, the Pb isotope of the detrital K-feldspar has been proved to be an effective provenance tool in determining sediment source regions, reconstructing palaeodrainage system and the whole-rock Pb isotopic composition of sand and silt could make a supple ment to the K-feldspar tracing work. According to the analysis of Pb isotopic heterogeneity from different tributaries, river geomorphology and hydrological characteristics for material＇s accessibility between the source and sink and geological environment of Yangtze River, we suggest that this method is feasible for constraining the source regions of sediment in Jianghan Basin and reconstructing the evolution of Upper Yangtze River. A few ideaon how to carrying out this research is also discussed.

关 键 词：碎屑钾长石 PB同位素 物源示踪 三峡贯通 

分 类 号：P597[天文地球—地球化学]