Abstract:

The thermal regime and thermal history of sedimentary basins play an important role in basin dynamics and hydrocarbon accumulation. The sedimentary basins in the western and eastern China underwent different tectonic background and dynamic mechanism, which resulted in the differentials of their thermal regimes. In this paper, the Meso-Cenozoic thermal regimes of the Bohai Bay Basin in the eastern China and Tarim Basin in the western China were studied based on the thermal history, “thermal” lithosphere and lithospheric thermal structure, and the results show that the thermal regimes in these two basins underwent different evolution since the Mesozoic. The heat flow of the Bohai Bay Basin underwent two peak evolution phases occurred in the Early Cretaceous to the early Late Cretaceous (K1K12) and the Eocene-Oligocene (E2E3) respectively, while the heat flow in the Tarim Basin gradually decreased from the Mesozoic to the Cenozoic. Two rapidly thinning processes of the “thermal” lithosphere in the Bohai Bay Basin occurred in the Late Early Cretaceous and the Paleocene, and its minimum thickness was only 4355 km in the Paleocene. However, the thickness of the “thermal” lithosphere in the Tarim Basin increased slowly in the Mesozoic and then rapidly since the Paleocene. The ratio of crust to mantle heat flow revealed that the lithospheric thermal structure of the Bohai Bay Basin was divided into two phases: “cold mantle and hot crust” type during the Triassic-Jurassic but “hot mantle and cold crust” type since the Cretaceous, while that of the Tarim Basin always stayed in the “hot mantle and cold crust” phase and then transferred to “cold mantle and hot crust” phase since the end of the Neocene. The differences of the lithoshperic thermal structures and thermal conditions between these two basins were closely related to the thermalrheological structure and deformation of the lithosphere. The research on the thermal history and lithospheric thermal structure of the sedimentary basins could effectively reveal the thermal regime in the deep of the sedimentary basins and
provide scientific reference for studying the basin dynamic mechanism during the MesoCenozoic.

Key words: Bohai Bay Basin, Tarim Basin, thermal history, thickness of “thermal&rdquo, lithosphere, lithospheric thermal structure