Sources of the Upper Proterozoic Terrigenous Deposits in the Northwestern Part of the Argun Massif, Central Asian Fold Belt: Results of U–Th–Pb Geochronological and Sm–Nd Isotopic-Geochemical Studies

The publication presents the results of geochemical, isotopic-geochemical (Sm–Nd) and isotopic-geochronological (U–Th–Pb) studies of terrigenous rocks of the Middle Riphean (?) Nadarov Formation and the Upper Riphean (?) Nortui Formation of the northwestern part of the Argun continental massif. The composition of the deposits indicates the presence of formations of various silica content in the source area. According to Sm–Nd data, sedimentary rocks of the Nadarov and Nortui formations are characterized by negative values of ε_Nd(t) = –6.6…–3.5 at Early Proterozoic values of Nd model age (t_Nd(DM) = 2.0–1.8 Ga). The U–Th–Pb dating of detrital zircon grains showed that the lower age limit of accumulation of terrigenous deposits of the Nadarov and Nortui formations falls to the Late Riphean (~775 and ~ 744 Ma, respectively). The main provenance areas for them were Late Riphean igneous rocks, with participation of Early Proterozoic rocks occurring in the Argun Massif.