Mesozoic-Cenozoic thermal evolution of the Linqing Sub-basin, Bohai Bay Basin (eastern North China Craton): Constraints from vitrinite reflectance data and apatite fission track thermochronology

The Linqing Sub-basin is situated in the south-west of the Bohai Bay Basin (BBB), which is the centre of lithospheric destruction and thinning of the eastern North China Craton (NCC). It is also one of China's premier hydrocarbon-bearing basins. To better understand the Mesozoic-Cenozoic thermal history of the Linqing Sub-basin, 178 vitrinite reflectance (Ro) data from nine wells and six apatite fission track (AFT) ages have been used. The effective AFT ages range from 53.5 to 107.7 Ma, with mean track lengths of 10.6 mu m, recording the tectonic-thermal events from the Early Cretaceous to the Palaeogene. The thermal modelling results of AFT show that the Linqing Sub-basin experienced two rapid cooling events during the Late Cretaceous (100-70 Ma) and Middle Eocene-Miocene (40-20 Ma), respectively, which are closely related to the subduction and rollback of the Pacific Plate. The thermal modelling results of Ro indicate that the Linqing Sub-basin has experienced two heat flow peaks during the Early Cretaceous and the Palaeocene-Late Eocene, with the heat flow values of 80 and 86 mW/m(2), respectively. These heat flow values were consistent with the destruction peak of the North China Craton and the extension peak of the Bohai Bay Basin. The Carboniferous source rocks experienced a large-scale hydrocarbon generation stage from the early Mesozoic to the Late Cretaceous and the Shahejie 3 Formation source rocks from the Middle Eocene to the Late Oligocene. Our study provides new geothermal evidence for the process of the destruction of the North China Craton.