准噶尔盆地构造—热演化特征

根据镜质体反射率动力学模型结合磷灰石裂变径迹参数,对准噶尔盆地各构造单元进行热演化模拟,结果表明:该盆地随地质历史的演化地温梯度逐渐减小,且各构造单元的地温演化不同.古生代时地温梯度较高,石炭纪时地温梯度达43.3～50℃/km,二叠纪末减小为36.3℃/km;中生代地温梯度减小,到三叠纪末为33.8℃/km,侏罗纪末为28.4℃/km,白垩纪末为24.8℃/km;第三纪以后地温梯度已接近于现今状况.盆地的这种地温演化与盆地3期大的构造运动密切相关.

TECTONO-THERMAL EVOLUTION IN THE JUNGGAR BASIN

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.