The Cenozoic Tectono-Thermal Evolution Of Depressions Along Both Sides Of Mid-Segment Of Tancheng-Lujiang Fault Zone, East China

There are many depressions along the both sides of the Tancheng-Lujiang (Tanlu) Fault zone,and their tectono-thermal evolution histories played an important role in the hydrocarbon generation and accumulation within the depressions. The thermal gradient evolution histories of 120 wells during the Cenozoic time in six depressions, which located along the middle part of Tancheng-Lujiang Fault Zone, were modeled by using the vitrinite reflectance and apatite fission track data in this paper. Based on these modeling results, the characteristics of thermal evolution of the Jiyang, Changwei, Linqing, Jizhong, Bozhong and Huanghua depression were analyzed. Generally, the thermal gradients of the different depressions decreased during the Cenozoic time. There had higher thermal gradients at Paleogene, but it only a little higher at Neogene than that of present-day' s. The modeling results of thermal history and the tectonic subsidence history reconstruction fits well with the evolution stages of rift-subsidence basin to down-warped basin. The thermal gradients are different in six depressions and decreases with the increasing distance to the Tanlu fault zone. There have higher thermal gradients in the depressions within the Tanlu Fault zone, such as Laohe basin, Bozhong and Changwei depression, with the gradient up to 57 similar to 59 degrees C/Km at the early Paleogene, and it maintained a higher level during the whole Cenozoic time in Changwei depression and Laohe basin. The relative lower gradient in the Bozhong depression was resulted from large amount of tectonic subsidence during the Neogene. However, the thermal gradients and their evolution in the Jizhong and Linqing depression, which far away from Tanlu Fault zone, was lower with 53 degrees C/km and 50 degrees C/km respectively at the early Paleogene. The above results show that the activity of Tanlu Fault zone at Cenozoic played an important role in the thermal fields of these depressions. The different thermal fields of the depressions along the both sides of mid-segment of the Tanlu Fault zone were macrocontrolled by the evolution of Tanlu Fault and partly controlled by the depression-controlling faults at the same time.