Abstract The mineralogy, major–element, and trace–element composition of shales, siltstones, and sandstones of the Uchur Group (Lower Riphean) and Aimchan and Kerpyl groups (Middle Riphean) in southeastern Russia were determined. The shales and siltstones are mostly illite to muscovite and quartz, with lesser K–feldspar, plagioclase, chlorite, carbonate, hematite, magnetite, and smectite. The sandstones are quartz–rich and range from quartz arenites and wackes to feldspathic arenites and wackes. They contain minor rock fragments (mostly shale or schist). Estimated CIA values (chemical index of alteration) of most shales and siltstones are fairly high (70–91) and ICV values (index of compositional variability) are less than one, suggesting fairly intense weathering in the source and no significant input of first– cycle material. A number of shales and siltstones of the Kerpyl Group have ICVs greater than one, suggesting that some first–cycle material was incorporated. The Eu/Eu* and (La/Lu) cn ratios of the shales–siltstones tend to decrease (0.75 to 0.65 and 13.8 to 7.8, respectively) and the Th/Sc ratios increase (0.76 to 0.95) from the Uchur to Aimchan to Kerpyl groups. These results suggest that the average source of the shales and siltstones changed from a more tonalite–rich source in the Uchur Group to a more granodiorite–rich source in the Kerpyl Group. The higher K–feldspar relative to plagioclase in the sandstones from the Uchur Group is thus anomalous, and it may have been a result of removal of the plagioclase due to intense weathering or diagenesis. Previous studies of the younger Neoproterozoic Lakhanda and Ui groups indicate that shales and siltstones have lower Eu/Eu* values than those of the Kerpyl Group. Thus, during the Mesoproterozoic the sources changed from a high abundance of tonalite in the Uchur Group to gradually increasing amounts of granodiorite in the Aimchan Group to more granite in the younger Lakhanda and Ui groups. Mesoproterozoic and Neoproterozoic (Riphean) shales in southeastern Russia have compositional trends in time similar to those from the southeastern USA and western Urals due to similar recycling (up to 70–75% of the rock volume) of original granitoid sources coupled with periodic input of first–cycle sediment. The Nd isotopes support mainly Paleoproterozoic (T Nd DM 1.9–2.4 Ga) sources for most groups, with Archean block erosional input (T Nd DM up to 2.8 Ga with moderately negative values of Nd) only for the Aimchan rocks. Younger Nd model ages (1500–1350 Ma) are observed in Early Upper Riphean (1025–1005 Ma) Lakhanda Group and Vendian Yudoma Group (< 560 –542 Ma) shales and correspond to juvenile input during late Grenvillian events (1000–950 Ma rift–related mafic magmatism along the eastern margin of the Siberia platform) and post–Rodinian (Vendian) destruction of the eastern periphery of the Siberian craton before opening of the Paleozoic ocean. The new data support the hypothesis of the existence of the supercontinent Rodinia (< 1050–600 Ma for the Siberian craton) but do not give direct evidence of Siberian juxtaposition to Laurentia during the Lower and Middle Riphean.