东秦岭-大别造山带北缘逆冲推覆构造特征及油气前景

东秦岭-大别山北缘逆冲推覆构造由南、北两支逆冲断裂组成,是联系东秦岭-大别造山带和南华北盆地的构造纽带。该逆冲推覆构造在走向上具有分段性,在倾向上具有分带性;即沿倾向分为前锋带、逆冲岩席带和根带;在走向上分为豫西逆冲推覆区段、周口南缘逆冲推覆区段和淮南-合肥逆冲推覆区段。构造演化分为3个阶段:印支期碰撞造山阶段、燕山晚期陆内造山阶段和燕山末期-喜马拉雅早期走滑拉张阶段。北缘逆冲推覆构造各区带烃源岩保存条件差异较大,油气显示集中分布在前锋带附近。评价前锋逆断带及前渊区(盆地/凹陷)为油气勘探最有利区带,南、北两支逆断带之间的逆冲岩席区(盆地/凹陷)为较有利区带。

Characteristics of overthrust structures on northern edge of East Qinling- Dabie orogenic belt and hydrocarbon potentials

Overthrust structure on the northern edge of East Qinling - Dabie orogenic belt consists of the southern and the northern overthrust faults, which constitutes the structural link between the East Qinling - Dabie orogenic belt and the southern North China basin. The overthrust structure is characterized by segmentation along the strike and zonation in the dip direction, i. e. it can be divided into frontal zone, overthrust sheet zone and root zone in the dip direction, and into Yuxi, southern edge of Zhoukou and Huainan - Hefei 3 overthrust segments along the strike. The tectonic evolution can be divided into 3 stages, namely Indosinian collision orogenic stage, late Yanshanian intracontinental orogenic stage and the end of Yanshanian - early Himalayan strike slip extension stage. The preservation condition of source rocks varies greatly in different zones and segments; and oil and gas shows are concentrated around the frontal zone. Therefore, the frontal thrust fault zone and the foredeep zone (basin/depression) can be evaluated as the most favorable areas for exploration, while the overthrust sheet zone ( basin/depression) that lies between the southern and northern thrust fault zones would be relatively favorable for exploration.