The First Evidence of Cambrian Granitoid Magmatism during the Formation History of the Bureya Continental Massif of the Central Asian Fold Belt

The results of U-Pb geochronological studies of Early Paleozoic granitoids from the northern part of the Bureya continental massif are presented. It has been established that porphyroblastic hornblende-biotite granites of the Kivili massif referring to the complex of the same name are of 502+6 Ma in age, while weakly gneissic biotite granites of the Kivity massif, Sularin complex, are of 492+6 Ma in age. Thus, granitoids of both complexes are of Cambrian rather than Ordovician age, as was previously assumed. In combination with materials already obtained, these data indicate that intensive granitoid magmatism manifested itself in the Middle Cambrian-Early Ordovician within the Bureya continental massif. It is noteworthy that, in the structure of the Jiamusi-Khanka continental massif, which is adjacent to the Bureya one, Early Paleozoic magmatism manifested itself in a broader range, which is from the Early Cambrian to the Silurian. This may indicate both differences in the formation history of these continental massifs and insufficient knowledge of the Bureya massif.