江汉盆地西北部断陷带构造变形分析与古应力场演化序列

Tectonic Deformation Analysis and Paleostress Field Sequence of the Grabens in the Northwestern Jianghan Basin

江汉盆地内部发育多个断陷带,其形成与演化对盆地油气聚集至关重要。本文以远安和南漳断陷带为重点,基于详细的野外观察和断裂变形测量,分析了江汉盆地西北部断陷带的构造变形特征,建立了盆地古构造应力场演化序列。结合区域构造分析与变形叠加特征研究,将断陷带白垩纪以来的构造演化历史划分为4个阶段:①晚白垩世—古近纪,受NEE—SWW向引张作用,江汉盆地内部发生断陷;②古近纪末期,断陷盆地遭受近E—W向挤压作用而发生构造反转;③新近纪,先后受NE—SW向引张和NW—SE向引张作用,断陷带再次伸展沉降;④新近纪末期,在NE—SW向构造挤压作用下,断陷带发生右旋走滑活动。江汉盆地晚白垩世以来构造变形序列的建立,为探讨江汉盆地后期构造演化及油气成藏改造提供了构造地质学证据。

Several grabens were developed within Jianghan Basin and their formation and evolution are essential to accumulation of oil and gas in the basin. With an emphasis on the Yuan＇an Graben and Nanzhang Graben in northwestern Jianghan basin and in combination with detailed field observation and measurement of faulting deformation, this study analyzed in detail the tectonic deformation of the northwestern graben zone of Hanjiang basin and established the stress field sequences. Based on the regional structures and superimposed deformation features in this area, the evolution history of the grabens in Jianghan Basin can be divided into four main stages： 1） Late Cretaceous to Paleogence, the grabens formed in Jianghan Basin due to an NEE--SWW-trending extension; 2） late Paleogence, the grabens deformed strongly by the E-- W-striking tectonic compression; 3） Neogene, controlled by NE--SW-trending extension and NW--SE- striking extension in turn, the grabens were extended again; 4） Late Neogene, dextral-slip activation occurred in the grabens clue to NE--SW-striking compression. The establishment of the structural deformation sequence of Hanjiang basin since Late Cretaceous provides structural and geological evidence for probing into the tectonic evolution of Hanjiang basin during the late stage and reformation of oil and gas accumulation.