Sources of Paleozoic granitic rocks and isotopic heterogeneity of the continental crust of the Aktau-Dzhungar microcontinent, Central Kazakhstan

摘要

Several generations of Paleozoic granitic rocks are studied with Sm-Nd isotopic methods in the northwestern part of the Aktau-Dzhungar microcontinent of Central Kazakhstan (Atasu-Mointy divide). The initial Nd isotopic composition of the granitic rocks varies in a relatively narrow range from-0.1 to-3.5 epsilon; the Nd model ages are also similar (1.11-1.46 Ga). These results indicate that the crustal source of all the Paleozoic granitic rocks of the region had similar composition and, probably, age. It is shown that the t (Nd)(DM) values of the Paleozoic granites reflect different proportions between ancient and juvenile material in the crustal source.