Home – Home – Jornals – Russian Geology and Geophysics 2026 number 9

We studied the chemical and isotope (C and O) composition of carbonate deposits and the age distribution of detrital zircon grains from the late Precambrian deposits of the Mana trough at the Sayan segment of the Central Asian Mobile Belt (CAMB). Limestones of the volcanosedimentary Kuvai Group (Mana and Bakhta formations) of oceanic genesis display high positive δ¹³C values, up to +8.9‰, which, along with other data, constrain their age to the Late Riphean (оr the late Tonian). The Angaloi Horizon strata have near-zero or slightly positive δ¹³C values, and the minimum detrital-zircon age is ca. 580 Ma, i.e., they can be assigned to the Late Vendian (or the late Ediacaran). In the upper part of the Anastas’ino Horizon, two pronounced positive δ¹³C excursions contrasting to near-zero values have been established; they mark the base of the Tommotian Stage (Cambrian). The age spectra of detrital zircons from the Angaloi Horizon and the lower bed of the Anastas’ino Horizon demonstrate two Neoproterozoic populations with peaks at 710 and 630 Ma. Zircons of these ages might have formed in volcanic and granitoid complexes at the Sayan segment of the CAMB. The presence of Paleoproterozoic zircon grains in the studied deposits suggests that the accretion of the sedimentary basin of the Mana trough to the Siberian Craton was completed in the early Cambrian. These conclusions are supported by geochemical indicators of the depositional environments of carbonates and by geodynamic reconstructions for the adjacent areas.