镜质体反射率在重建盆地古地温中的应用──中国东部、西部中、新生代沉积盆地古地温特征

Application of Vitrinite Reflectance in Reconstruction of Paleotemperature: Evolution of Paleotemperature in the Eastern and Western Mesozoic-Cenozoic Sedimentary Basins,China

在总结前人关于镜质体反射率重建盆地古地温方法的基础上，讨论了各方法的理论基础、应用效果及其局限性。选择理论上与实际应用效果较好的EasyR0方法，重建了东部苏北盆地、辽河盆地和西部柴达木盆地、三塘湖盆地典型探井的古地温演化模式。结果表明我国东部中、新代大陆架谷型盆地，具有比酉部中、新生代前陆型盆地更高的古地温梯度。中生代末至第三纪早期，东部盆地的古地温梯度大于4．0℃／100m，而西部盆地的在3．0～2．5℃／100m。我国中、新生代沉积盆地古地温普遍具有从高到低的演化趋势，而柴达木盆地则相反，古地温梯度自早第三纪的2．5℃／100m升高到现今的3．0℃／100m。这几个盆地古地温的成功恢复，证实EasyR0方法对热演化各异的不同类型盆地古地温恢复具有广泛的适应性，而且，准确性高。过去常用的TTI－R0方法过高地计算了有机质的成熟度，使重建的古地温偏低。

Comparison and discussion were carried out with various methods,using vitrinite reflectance(VR) to reconstruct paleotemperature of sedimentary basins. It was perceived that the Easy R0 algorithm is the most accurate method for prediction of VR and then for palcotemperature throughout the range Of organic maturity normally encountered. The Easy R0 model was wsed to restore paleotemperature gradients(PG) of four sedimentary basins in the eastern and western China,respectively. It was indicated that the eastern basins characteristic of continental rift basin had higher paleotemperature gradients in the Mesozoic-Cenozoic Era than those characteristic of foreland basin in the western China. The eastern basins had more than 4. 0℃/100m of PG from the Late Mesozoic to Early Cenozoic Era,but lower than 3. 0～2. 5℃/100m in the western basins of China during the same period. Three of the four basins concerned, Liaohe Basin,subei Basin in the east and santanghu Basin in the west,had a decreasing evolution in PG in Late Mesozoic,while Qaidarn Basin underwent an increasing evolution in PG,from 2. 5℃ /100m to nowadays 3. 0℃ /100m. The success of PG reconstructions for four basins suggested that the Easy R0 algorithm is suitable to PG reconstruction of various tectonically different basins.