Provenance of late Paleozoic sedimentary rocks in eastern Kazakhstan: Implications for the collision of the Siberian margin with the Kazakhstan collage

Abstract

• The sedimentary provenance is different across the Char Shear Zone in eastern Kazakhstan. • The Char Shear Zone represents the suture between the Siberian margin and the Kazakhstan collage in eastern Kazakhstan. • The oceanic basin between the Siberian margin and the Kazakhstan collage was closed after 321 Ma. To unravel when, where, and how multiple arc systems were amalgamated is crucial for understanding the accretion processes of the Central Asian Orogenic Belt. Here we focus on the collision of the Siberian margin and the Kazakhstan collage along the Char Shear/Suture Zone in eastern Kazakhstan. We conducted U–Pb dating and Hf isotope analysis for detrital zircons of clastic rocks across the collisional zone of the Siberian margin (the Irtysh-Zaisan Complex) and the Kazakhstan collage (the Zharma-Saur Arc and the Char Zone). Our results show that the Irtysh-Zaisan Complex carries abundant early Paleozoic detrital zircons and minor Precambrian zircons, but there is a lack of such zircon populations in the Zharma-Saur Arc and the Char Zone. Devonian to Carboniferous detrital zircons appear in all sampling tectonic units, in which ε Hf (t) values of Carboniferous zircons from the Zharma-Saur Arc and the Char Zone are characterized by a narrow range (∼10–17) that is different from a relatively wider range of ε Hf (t) values of ∼5–18 for the Carboniferous zircons in the Irtysh-Zaisan Complex. The distinct sedimentary provenances of the Irtysh-Zaisan Complex and the Zharma-Saur Arc/Char Zone confirm that their tectonic boundary lies along the Char Shear Zone in eastern Kazakhstan. As the Late Carboniferous sedimentary rocks from the Zharma-Saur Arc and the Char Zone do not receive detritus from the Siberian margin, we consider that the Ob-Zaisan Ocean between the Siberian margin and the Kazakhstan collage was closed later than the deposition of these sedimentary rocks (<321 Ma).