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. Features of the material composition of the deposits indicate the presence of formations of various silicia acidity in the source area. According to Sm–Nd data, sedimentary rocks of the Nadarov and Nortui formations are characterized by negative values åNd(t) = –6.6…–3.5 at Early Proterozoic values of Nd model age (tNd(DM) = 2.0–1.8 Ga). According to U–Th–Pb dating of grains of detrital zircon, it was defined that the lower age limit of accumulation of terrigenous deposits of the Nadarov and Nortui formations falls at the Late Riphean (~775 and ~ 744 Ma, respectively). The main provenances area for them were Late Riphean igneous rocks with the participation of Early Proterozoic rocks, extended in the structure of the Argun massif.