Age of Detrital Zircon and Composition of Cambrian−Ordovician Terrigenous−Carbonate Deposits in Middle Reaches of Vilyuy River, Southern Siberian Platform

The data obtained from lithological and mineralogical study of the Upper Cambrian and Lower Ordovician terrigenous−carbonate deposits in the middle reaches of the Vilyuy River, southern Siberian Platform are discussed. The study of detrital zircon, garnet, and tourmaline in the sample from the Upper Cambrian Kholomolokh Formation and two samples from the Upper Cambrian to Lower Ordovician Balyktakh Formation revealed that the main sources for the studied minerals are acidic and intermediate igneous and metamorphic rocks, amphibolite-facies metasediments, and amphibolite to granulite-facies metamorphosed mafic−ultramafic complexes of the Precambrian Siberian Craton basement. The U−Th−Pb zircon dating from the Kholomolokh and Balyktakh Formations in the middle reaches of the Vilyuy River revealed a significant difference in the provenance areas of terrigenous material in the Late Cambrian and Ordovician. In the sample from the Upper Cambrian Kholomolokh Formation, zircon represented by a younger population is characterized by predominance of Neoproterozoic ages (peak values are 550 and 845 Ma). This indicates that rocks of the Neoproterozoic terranes of the southern margin of the Siberian Craton were the main provenance area in the Precambrian. Paleoproterozoic zircon (1880‒1890 Ma) is main population in the Early Ordovician rocks of the Balyltakh Formation (~70%). In the Early Ordovician, the most probable source of matter for the Vilyuy syneclise was an uplift of the Archean−Paleoproterozoic basement located in the central part of the Siberian Platform. Nearly complete absence of younger zircon (~500−900 Ma) in the Balyktakh Formation deposits indicates a weak effect of provenance located at the southeastern margin of the Siberian Platform in the Ordovician time.