Age and formation features of the Ordovician Chalovskaya sequence in the Argun Massif, eastern part of the Central Asian fold belt

Abstract

In this paper we present the results of the mineralogical and geochemical studies of metaterrigenous rocks of the Grebnev and Magdagachi formations of the Chalovskaya Sequence – one of the key stratigraphic divisions of the Argun continental Massif in the eastern part of the Central Asian fold belt, and U–Pb geochronological (LA-ICP-MS) data for the detrital zircons from these rocks. It is established that the youngest zircons in the metasandstones of the Grebnev Formation have an age of ~478 Ma, and in the metaalevrolites of the Magdagachi Formation ~448 Ma. Together with the previously obtained data on the age of metadacites from the Isagachi Formation (476 ± 8 Ma), this information indicates the Ordovician age of the Chalovskaya Sequence, previously attributed to the Late Precambrian. It was shown that the accumulation of sediments of the Chalovskaya Sequence took place in an environment of an active continental margin or island arc simultaneously with intense magmatic activity. Taking into account the fact that the Early Paleozoic suprasubduction magmatism manifested within all the continental massifs of the eastern part of the Central Asian fold belt (Argun, Mamyn, Bureya, Jiamusi, Khanka), it cannot be excluded that the mentioned continental massifs have a common geodynamic history.