Age and Tectonic Setting of Granitoids of the Uda Complex of the Dzhugdzhur Block of the Stanovoy Suture: New Data on the Formation of Giant Magmatic Belts in Eastern Asia

摘要

Granitoids of the Uda complex are distributed within the southeastern marginal part of the Siberian craton and its folded framing. Geochemical, isotope (Nd, Sr), and geochronological (U–Pb ID TIMS) studies of two massifs (Chalbuk-Yakon and Uyan-Tavitchak) of this complex of the Dzhugdzhur Block of the Stanovoy suture were carried out; the results are presented in this paper. It is found that formation of these massifs took place in the Early Cretaceous (116 ± 1 Ma) in the geodynamic setting of lithospheric extension. The initial magma for these granitoids was formed from a mixed source: Early Precambrian lower crust and mantle, with a clear predominance of the crustal component. The granitoids of the Uda complex of the Dzhugdzhur block most likely represent the eastern end of the Udsko-Zeya (Stanovoy) post-collision magmatic belt, stretching for more than 1000 km along the southern framing of the Siberian craton parallel to the Mongol–Okhotsk suture zone and stitching various tectonic blocks of the northeastern part of the Central Asian fold belt. There is every reason to believe that, further to the west, the Udsko-Zeya (Stanovoy) belt passes into the West Transbaikal rift system, the formation of which took place in the interval of 170–110 Ma. In other words, it can be assumed that in the Mesozoic, in the southern framing of the Siberian craton, there was a giant unified rift system stretching for more than 2000 km.