浑善达克沙地的碎屑锆石U-Pb年龄和Hf同位素组成及其源区意义

Detrital zircon composition of U-Pb ages and Hf isotope of the Hunshandake sandland and implications for its provenance

通过对浑善达克沙地末次冰盛期(LGM)以来沙样的碎屑锆石原位U-Pb年龄和Hf同位素组成的分析,并与周围可能源区的岩石年龄和Hf同位素组成进行对比,发现浑善达克沙样的U-Pb年龄主要可以分为3组(2.6～2.3Ga,2.2～1.6Ga和显生宙100～500Ma)。其中较老的两组和具有负ε_(Hf)(T)值的显生宙锆石可能来源于华北克拉通北部的燕山褶皱带,而具有正ε_(Hf)(T)值的显生宙锆石可能来源于中亚造山带东部。现代沙和LGM沙具有相同的锆石U-Pb年龄谱和ε_(Hf)(T)组成特征。同时,与蒙古中南部和塔里木中部沙样进行对比,发现蒙古中南部沙样主要来源于中亚造山带的显生宙高山,而塔克拉玛干沙漠在锆石U-Pb年龄和Hf同位素组成上与浑善达克沙地存在较大的差异,表明西部的大沙漠对东部沙地的贡献很小。

Abstract Detrital zircon compositions of in-situ U-Pb ages and Hf isotope were measured for sand samples since the Last Glacial Maxim （LGM） from the Hunshandake sandland, and compared with surrounding potential source areas. We found that U-Pb age spectra of samples from the Hunshandake sandland can be mainly divided into three groups （2.6 ～ 2.3Ga, 2.2 ～ 1.6Ga and Phanerozoic age 100～ 500Ma）. The older two groups and some Phanerozoic zircons with negative БHf（T） values maybe were derived from the Yanshan Fold Belt in the northern part of the North China Craton, and other Phanerozoic zircons with positive БHf（T） values may originated from the eastern part of the Central Asian Orogenic Belt. The present sands have the similar composition characteristics of zircon U-Pb age spectra and БHf（T） values with the LGM sands. Meanwhile, comparing with the sand samples from central-southern Mongolia and central Tarim, we found that the sand samples of central-southern Mongolia mainly come from Phanerozoic high mountains of the Central Asian Orogenic Belt, however, much difference of zircon U-Pb ages and Hf isotopes occurs between the samples of the Hunshandake and Taklimakan deserts, indicating that the material of the western large desert contributes little to the eastern sandland.