Evolution of the Central Asian Orogenic Belt along the Siberian margin from Neoproterozoic-Early Paleozoic accretion to Devonian trench retreat and a comparison with Phanerozoic eastern Australia

Abstract

The Central Asian Orogenic Belt (CAOB), the largest accretionary orogen on Earth, has received considerable attention in the last 25 years. Various models have been proposed to explain the evolution of the CAOB, incorporating processes such as the lateral duplication of one single arc system along large shear zones, terrane accretion/amalgamation, oroclinal bending, ridge subduction, and trench migration. To better understand accretionary processes along the southwestern Siberian margin, we synthesized new and published detrital zircon and Hf isotope data from various tectonic units along the southwestern Siberian margin. Our results show that the accretion of microcontinents and island arcs might have dominated the southwestern Siberian margin in the Neoproterozoic. This was followed, during the Early Paleozoic, by the development of a very large accretionary wedge system. An abrupt increase of zircon εHf(t) during the earliest Devonian is explained by a major phase of trench retreat. A comparison of our results with another major Phanerozoic accretionary orogen, the Tasmanides in eastern Australia, shows a similar behavior of episodic trench retreat. We further suggest that the Late Mesozoic to Cenozoic fragmentation of the eastern Gondwanan margin, and the formation of multiple island arcs within marginal sea basins in the southwestern Pacific Ocean, is a possible analogue for the Late Paleozoic development of the East Junggar island arc system in the CAOB.