敦煌地块变质岩系时代新认识

详细信息

NEW SPECULATION OF THE AGE OF THE METAMORPHIC ROCK SERIES OF THE DUNHANG MASSIF

摘要: 敦煌地块的中深变质岩系敦煌群，经１／５万区调获得Ｓｍ－Ｎｄ等时线年龄值２９３５Ｍａ、２９４６Ｍａ、３４８７Ｍａ，归属于太古界。北山南带的中深一浅变质岩系，经１／５万区调及１／２０万区调修测，在中深变质岩系中获得Ｓｍ－Ｎｄ等时线年龄值２９４９Ｍａ、２９５６Ｍａ、３２３７Ｍａ及２２０３Ｍａ、２０５９Ｍａ，分别划归敦煌群和厘定为早元古代。在浅变质岩系中获得Ｓｍ－Ｎｄ等时线年龄值１６２２Ｍａ、１６２４Ｍａ及Ｂａｉｃａｌｉａ等叠层石，归属于中上元古界。

Abstract: During 1:50000 regional surveys.the Dunhuang Group of the intermediate-and high- grademetamorphic rock series in the Dunhuang massif was determined to have Sm-Nd isochron age val-ues of 2935Ma , 2946Ma and 3487Ma,belonging to the Archean, Samples from the intermediate-and high-grade metamorpnic rock series in the south zone of the Beishan Mounains gave Sm-Ndisochron age values of 2949Ma,2956Ma,3237Ma ,2203Ma and 2059Ma,which are respectively as-signed to the Dunhuang Group and determined to be of Proterozoic age. Stromatolites such asBaicaliia were collected from the low-grade rock series and ages of 1622 Ma were obtained,so theseries is assigned to the middle Upper Proterozic.