Early Paleozoic magmatic events in the Bureya Continental Massif, Central Asian Orogenic Belt: Timing and tectonic significance

Abstract

The Bureya Massif is one of the largest continental massifs in the eastern Central Asian Orogenic Belt. The reconstructions of tectonic scenarios for the evolution of this belt are mainly based on geochronological and geochemical data. However, relevant data from the Bureya Massif are scarce. Here, we report whole-rock geochemistry, zircon U-Pb geochronology, and Lu-Hf isotope data for Early Paleozoic granite intrusions to constrain the timing of the magmatic and tectonic processes in the Bureya Massif. Geochronological data yielded ages of 495 ± 5, 486 ± 8, 471 ± 6, 453 ± 2, and 426 ± 6 Ma for the granitoids in the Bureya Massif. The chemical composition of the Early Paleozoic granitoids mostly showed affinities to A-type (A2-subtype) granites. Furthermore, they have zircon εHf(t) values of −5.3 to +5.7, and two-stage model ages tHf(C) of 1.52–0.95 Ga. These results suggest that the parental magmas of the Early Paleozoic granitoids were derived either from melting of a dominantly Neo- and Mesoproterozoic crustal source. Early Paleozoic magmatism in the Bureya and Songnen–Zhangguangcai Range massifs was characterized by similar timing and identical Hf-in zircon isotope compositions. Additionally, both arrays contain early Neoproterozoic granitic intrusions and Early Cambrian and Ordovician sedimentary units, suggesting that they were part of a single continental massif at the beginning of the Cambrian or even in the Neoproterozoic. In this case, the tectonic nature of the Early Paleozoic magmatism in these two massifs should be the same and was probably related to the docking of the Jiamusi Massif.