Palaeogeothermal response and record of the effusing of Emeishan basalts in the Sichuan basin

Abstract

Thermal history of the Sichuan basin is reconstructed based on vitrinite reflectance from boreholes in the basin using a paleo-heat flow method. The results show that the Sichuan basin experienced a relatively low heat flow period in the Early Paleozoic, and an elevated paleo-heat flow, ranging 60∼80 mW/m2 with a maximum as high as 100 mW/m2 around 259 Ma, from the beginning of the Late Paleozoic to the end of the early Permian, and a decreased paleo-heat flow from the late Permian to the late Triassic, and then maintained nearly stable to the present-day. The Late Paleozoic paleo-heat flow was quite high where there were extensive Emeishan flood basalts or concealed basalts which erupted between the early and the late Permian, such as the southwestern and northeastern areas of the Sichuan basin. According to the distribution of paleo-heat flow, it can be inferred that, the northeastern Sichuan basin was also influenced by the Emeishan magmatic activity during the Dongwu movement though there were lack of Emeishan flood basalts. In addition, the results of thermal history reconstruction of the Sichuan basin provide paleogeothermal evidence for the existence and onset of the Emaishan mantle plume.