Late Mesozoic tectonic evolution of the Songliao basin, NE China: Evidence from detrital zircon ages and Sr-Nd isotopes

The Songliao basin, situated between the Siberian and Sino-Korean (North China) cratons, was tectonically shaped by convergence of the Mongol-Okhotsk and Paleo-Pacific oceans. The lack of isotopic and geochemical data from its sedimentary rocks has hindered a better understanding of the depositional-tectonic history of the basin so far. A continuous sedimentary sequence is preserved in the upper part of the Songliao basin (Denglouku and Quantou formations). These rocks provide clues to depositional processes operating in this region during the late Cretaceous. Dominant zircon populations of the underlying Denglouku Formation are largely Paleozoic (270-250 Ma) and Mesozoic (190-170 Ma) in age, whereas the overlying Quantou Formation contains mostly older zircon populations of similar to 1800 Ma and similar to 2500-2900 Ma. The youngest detrital zircons place the deposition ages of both rock formations at about similar to 117 Ma and similar to 103 Ma, respectively. The Denglouku Formation is characterized by less negative initial epsilon(Nd) values (-6.3 to -2.8), younger Nd model ages (1.05-1.39 Ca) and lower initial Sr-87/Sr-86 ratios (0.7079 to 0.7088), compared to the Quantou Formation (-12.8, 1.75 C a and 0.7129), confirming that both formations were derived from different source areas. Our data suggest that Paleozoic and Mesozoic magmatic rocks were widespread in the northern periphery of the basin, and served as potential sources of the Denglouku Formation. In the south-east, old basement rocks of the North China craton provided sedimentary material for the Quantou Formation. The south-eastward migration of erosion center(s) in the Songliao basin in the late Mesozoic probably resulted from an abrupt change in basin uplift and subsidence. These processes were driven in response to regional tectonic changes toward an increasing dominance of the Pacific Ocean over the Mongol-Okhotsk Ocean subduction regime. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.