The Effect of Emeishan Supper Mantle Plume on the Thermal Evolution of Hydrocarbon Source Rocks in the Sichuan Basin

Abstract

AbstractBoth the structural evolution and thermal history of the Middle ‐ Late Permian Sichuan Basin are closely related to activity of the Emeishan Supper Mantle Plume (ESMP). The ESMP played an important role in the thermal evolution of the pre‐Middle Permian hydrocarbon source rocks in the southwestern part of the Sichuan basin. On the basis of reconstructed thermal history of the Sichuan basin, based on vitrinite reflectance (Ro) from boreholes in the basin, using a paleo‐heat flow method, the effect of the ESMP on the evolution of the pre‐Middle Permian source rocks is studied. The results show that in the southwestern part of the Sichuan Basin (the intermediate zone of the ESMP) the organic matter of the Paleozoic source rocks became mature in middle Late Permian. This indicates that the thermal evolution of the Paleozoic source rocks was strongly affected by the ESMP. In more detail, in the region close to the ESMP, the source rocks of lower Permian were heated to peak maturity (maximum Ro > 3%) at around 260 Ma and later there was no secondary hydrocarbon generation. However, in the regions far away from the ESMP, secondary Mesozoic hydrocarbon generation of the source rocks existed. The thermal evolution of the Mesozoic source rocks was related with Mesozoic foreland basin evolutionburial history and subsequent regional denudation of the basin, rather than the ESMP. Therefore, except in the regions far away from the ESMP, the prospect of oil and gas from Paleozoic source rocks is unfavorable.