Abstract:
This paper presents new data on the age and composition of granitoids from the Charnokitovyǐ and Drevnestanovoy complexes of the Dambukinskiǐ block in the eastern Dzhugdzhur-Stanovoy fold belt. Based on the results of U-Pb zircon geochronology, including single grain dating, it was shown that these granitoids are 2833±15 and 2828±34 Ma old, respectively, and experienced structural and metamorphic transformations corresponding to at least two events of high-temperature regional metamorphism of Late Archean (2647 ± 3 Ma) and Early Proterozoic (1884 ± 9 Ma) ages. The former was probably related to the accretion of the small terranes that now build up the ancient granulite basement of the Dzhugdzhur-Stanovoy fold belt and their attachment to the Olekma-Aldan continental microplate. The second metamorphic event was probably caused by the collision of the Dzhugdzhur-Stanovoy microplate and the Siberian craton, when the Early Proterozoic ocean basin between them closed. Our geochronological, isotopic (Sm-Nd and Pb-Pb), and geochemical results suggest that the generation of the parental melts of the Charnokitovyǐ and Drevnestanovoy granitoids reflected the occurrence of crust-forming processes 2.9-2.8 Ga ago. They were younger than the Late Archean crust-forming events that have been recognized up to now in the Aldan shield.