Evolution and deep structure of the Zeya-Bureya and Songliao sedimentary basins (East Asia)

The evolution and deep structure of the Songliao and Zeya-Bureya basins can be divided into the rift, platform (subsidence), and neotectonic phases. The rift phase (Middle Jurassic-Early Cretaceous) climaxed at the formation of a basin-wide near N-S-oriented rift system, which was followed (Late Cretaceous) by the deposition of the deep-water organic-rich lacustrine source facies with the maximum thickness identified in the Songliao basin (up to 1100 m). The neotectonic phase was marked by the pronounced differences in the basin's development caused by the formation of a series of E-W-trending transverse structures, which eventually separated the basins, changed the drainage pattern, and blocked the rivers draining southwards from the Zeya-Bureya to the Songliao basin. The differences in the deep structure of the basins are also strongly pronounced. High heat flow values of more than 70 mW/m(2) are typical of the Songliao basin, and its mantle heat flow component is higher than the crustal one, as compared to the Zeya-Bureya basin (below 50 mW/m(2)). The crustal thickness of the Zeya-Bureya basin is higher than that of the Songliao basin (38-42 km and 29-34 km) with a lithospheric thickness of 110-140 km and 50-75 km, respectively. The only exception is the southern Zeya-Bureya basin, which has an electrical structure similar to that of the Songliao basin. These differences have important implications for the evaluation of the hydrocarbon potential of the rift basins. It was suggested that the evaluation of the hydrocarbon potential of the sedimentary basins or parts of these basins should account for two factors: (1) the influence of the lithospheric motions and the related collisional processes and (2) the anomalies in the deep lithospheric structures (the high heat flow and the reduced crustal and lithospheric thickness). The results of this study indicate that the southern part of the Zeya-Bureya basin (in particular, the Lermontovka, Dmitrievka, Mikhailovka, Ekaterinoslavka, and Arkhara troughs) is interpreted to have a fairly high hydrocarbon potential.