Thermal evolution and dynamic mechanism of the Sichuan Basin during the Early Permian-Middle Triassic

Abstract

The Sichuan Basin, located in the western margin of Yangtze Plate, is one of the important oil-gas-bearing basins in China. During the Early Permian-Middle Triassic, the Sichuan Basin experienced regional lithospheric extension and Emeishan basalt activities, both of which influenced the basin development and thermal evolution. Here we simulated the thermal effects of lithospheric extension and the Emeishan mantle plume based on different geodynamical models. Modeling results indicated that the lithospheric temperature together with the basement heat flow was generally increasing with time due to extension. As the stretching factor was relatively small, the thinning of lithosphere, and consequently the thermal disturbance, was not great. The lithospheric extension yielded about 20% increase of the basement heat flow, with maximum value of 60–62 mW m⁻² in the Early Triassic. Mantle plume model shows that the thermal evolution of the inner zone above the plume head was influenced greatly by plume activity. But the outer zone and its outside area where the Sichuan Basin is located were affected only slightly. The basalts that had erupted in the southwestern basin might disturb the basin temperature significantly, although shortly and locally. Generally, the thermal history of the Sichuan basin during the Early Permian-Middle Triassic was controlled by the lithospheric extension, but locally it superimposed thermal effects of basalt activities in its southwestern area.