Interaction between the Central Asian Orogenic Belt (CAOB) and the Siberian craton as recorded by detrital zircon suites from Transbaikalia

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This study was carried out to determine the initial age and time-span of interaction of two major crustal provinces of Asia: the Siberian craton and the Central Asian Orogenic Belt (CAOB). Single grain U–Pb ages of detrital zircon suites from the Neoproterozoic passive margin strata of the Siberian craton were used to determine the first appearance of extraregional source regions. Twelve Neoproterozoic clastic rocks from the Baikal-Patom margin of Siberia and one sample from the volcaniclastic Padrinsky Group that was deposited unconformably above accreted CAOB crust were analyzed. In total, 1152 grains were analyzed, 703 were used for provenance interpretation. Stratigraphically lower strata from the Siberian margin yield Archean – Paleoproterozoic detrital zircon ages, which are similar to, and probably derived from the Siberian Precambrian craton. A few extra-regional Mesoproterozoic grains are also present.The provenance shift happens in the upper portion of the section and is marked by the influx of extra-regional zircons. The youngest included zircons (610Ma) constrain the age of deposition and provide evidence for the timing of initial interaction between CAOB and Siberia in this region. Neoproterozoic zircons also dominate the overlying sedimentary units of the CAOB, suggesting continuing convergence. Coeval volcaniclastic unit deposited across the accreted CAOB terrane has a similar U–Pb detrital zircon age distribution, strengthening the provenance links between the two sides of the orogen.Analysis of the local tectonics suggests that the beginning of accretion might have started even before the first appearance of Neoproterozoic zircon: during the development of a regional unconformity, capped by 635Ma (?) “Snowball Earth” tillites of Dzhemkukan Formation. The absence of Neoproterozoic zircons in Dzhemkukan Formation is probably explained by the absence of development of an extremely thickened crust.Our data are in good agreement with data collected from other Neoproterozoic sedimentary basins of southern Siberian craton, including Cisbaikalia and Bodaibo Synclinorium.