金沙江中段元古宙变质岩的Sm-Nd同位素年龄报道

金沙江中段的古老变质岩由多期变质的元古宙变质岩石单元组成。利用Sm-Nd同位素方法获得了雄松群二云母片岩全岩同位素等时线年龄1594Ma和1723Ma、2011Ma两组模式年龄。前者代表了成岩年龄,后者代表金沙江中段地层的基底年龄,这与金沙江流域乃至整个华南地壳最初形成的年龄十分相似。表明,川西、藏东地区雄松群变质岩可能属于华南地壳的组成部分。其形成时间应在早元古代或更早的时期内。

Sm-Nd ISOTOPIC AGES OF PROTEROZOIC METAMORPHIC ROCKS FROM THE MIDDLE SECTOR OF THR JINSHA RIVER

Whole-rock Sm-Nd isochron ages and Nd model data of six samples from theXiongsong Group metamorphic rocks in the middle sector of the Jinsha River arereported here. The results show that the isochron ages of muscovite-biotite schistis 1 594 Ma, the Nd model ages may be classified into two groups: their averageages are 1 723 Ma and 2 011 Ma respectively. The diagenetic age of the XiongsongGroup appears to be 1 594 Ma. The Nd model ages of 1 723 Ma and 2 011 Ma arevery close to those of the continental crust of southern China (the reaches of theJinsha River and the Yangtze River). The present Xiongsong Group metamorphicrocks of western Sichuan and eastern Tibet might belong to continental crust ofsouthern China. They might be initially formed in the early Proterozoic or evenearlier.