Recycling of Clastics and Detrital Zircon during the Formation of Sedimentary Sequences of the Riphean Stratotype

Abstract

The lithochemical features of clastic rocks at several stratigraphic levels of the Riphean stratotype (Ai, Bakal, Zigalga, Zil’merdak, and Uk formations), as well as the distribution of detrital zircon populations in the sandstones therein, are analyzed. The clastics in the Riphean stratotype section show two main formation trends—entry into the cycle 1 sedimentation area (petrogenic) and recycled (redeposited, lithogenic) material. It is suggested that the detrital zircon, delivered from protosources into sandstones of the Ai stratigraphic level, was repeatedly subjected to redeposition: crystals with close maximums on the probability density curve are present in sandstones of younger stratons of the Riphean-type section, up to the Uk Formation. The most striking renewal of detrital zircon protosources occurred at the beginning of the Late Riphean. The arkosic and subarkosic sandstones of the Bir’yan Subformation of the Zilmerdak Formation contain both detrital zircon with ages similar to those in the sandstones of the Lower and Middle Riphean, as well as new zircon characterized by Paleo- and Mesoproterozoic maximums on the probability density curve. A small part of such new zircon is repeated in the oolitic limestones of the Uk Formation, but some renewal of protosources is also recorded here. Thus, the Middle/Late Riphean boundary was marked by a radical change in age populations of the detrital zircon, probably, related to the formation of a fundamentally new system of the clastic material transport from sources to sink.