大陆地壳演化时间维的确定及存在问题

DETERMINAfION OF CHRONOLOCICAL DIMENSIONS OF THE EVOLUTION OF COMINEMAL CRUST AND EXISTING PROBLEMS

在大陆地壳演化研究中，时间维的确定具有十分重要的意义。讨论了应用最广泛的Ｕ－Ｐｂ法和等时线法的适用性及存在的问题。指出对Ｕ－Ｐｂ年龄研究过程中需要加强成因矿物学研究，而对等时线年龄必须根据基本原理对等时线进行合理性判别，以决定样品的取舍。以Ｓｍ－Ｎｄ法为代表，讨论了Ｓｍ－Ｎｄ等时线年龄和Ｕ－Ｐｂ年龄所代表的地质内涵。最后对新疆近年来同位素年代学所取得的进展做了简要评述。

The determination of chronological dismensions is very important for studying the evolution ofthe continental crust. The U-Pb method and isochronism method most widely used are discussed in terms of the adaptability and existing problems. For U-Pb saes, the study of senetic mineralogy needs to bestressed, while, for isochronic saes, a reasonable.discrimination of the isochronic lines should be given inprinciple for the selection of samples.The geological intension of Sm-Nd isochronic ages and U-Pb agesare then discussed. Finally the progress in isotopic chronology acquired recently in Xinjiang is reviewed.