1. Key Laboratory for Petroleum Entrapment Mechanism in the Ministry of Education, University of Petroleum, Beijing 102249; 2. Institute of Petroleum Exploration and Development, Xinjiang Oil Field Comp
The thermal evolution of the main tectonic units in the Junggar Basin was modeled based on the EASY% R o model of vitrinite reflectance and annealing model of apatite fission track. The modeling results showed that the thermal gradients decreased with the evolution of the basin and with different characteristics in the six main tectonic units. The thermal gradient could be up to 43.3～50℃/km at the Carboniferous time, decreasing to 36.3℃/km at the end of Permian, 33.8℃/km at the end of Triassic, 28.4℃/km at the end of Jurassic and 24.8℃/km at the end of Cretaceous, respectively. The thermal gradient distributed nearly the same with the present day’s since Tertiary. This thermal evolution related closely with the three tectonic movements in the basin, namely, the Late Hercynian orogeny when the volcanic activities widely occurred, the Indosinian Yanshanian orogeny in Mesozoic and the Himalayan orogeny in Cenozoic.