湘鄂西中生代弧形叠加扩展的变形记录

Deformation record of multi-stage overprinting and expansion of the Mesozoicarcuate structure in western Hunan and Hubei

通过对湘鄂西构造带进行大量的构造形迹测量、解析,结合研究区内构造变形年龄数据的统计分析。明确燕山中期(J;—K_(2))早期弧形构造弧顶方向为330°,并向两侧发散状分布,以大别山、黔中、黄陵隆起为约束点,湘鄂西形成了由南东侧至北东侧构造迹线由NE→NEE→EW→NWW逐渐偏转的弧形构造,最大主应力方向偏转近114°。同时早期弧形构造扩展过程中,分别会在弧形构造两翼,形成近SN向(大耳山-茶园断层、乌江-大千断层)和NW向走滑断裂(仙女山断层);燕山晚期(K_(2)末期—K_(2))晚期弧形构造弧顶方向为296°,由于受到齐岳山断裂的影响,晚期弧形构造分成两幕,K_(2)末期(燕山晚期弧形一幕形成)、K_(2)(燕山晚期弧形二幕形成时期)。以大巴山、黔中、黄陵隆起为约束点,湘鄂西形成了由南东侧至北东侧构造迹线由SN向NE逐渐偏转的弧形构造,最大主应力方向偏转近86°。并逐渐向四川盆地扩展,至到华蓥山断裂。两期弧形构造影响强度范围有一定的差异,研究区北东侧以燕山中期弧形构造主控,西南侧以燕山晚期弧形构造主控,造就湘鄂西北东侧与西南侧油气藏赋存的差异。

Based on a large number of tectonic trace measurements and analysis of the western Hunan and Hubei tectonic belt, this study is a statistical analysis of tectonic deformation age data in the study area. It is clear that the early arc structure of the mid-Yanshan(J;—K_(2)) has a top direction of 330° and diverges on both sides, with Dabie Mountain, central Guizhou and Huangling uplifts as the restraining points, and the western Hunan and Hubei formed arc structure from the southeast to the northeast whose construction trace gradually deflected from NE→NEE→EW→NWW, and the direction of the maximum principal stress deflected nearly 114°. At the same time, during the early expansion of the arc structure, near SN directions(the Daershan-Chayuan and the Wujiang-Daqian faults) and NW strike-slip fault(the Xiannvshan fault) were formed on both wings of the arc structure;the arc top direction of the late-arc structure developed in the late Yanshan(K_(2)—K_(2)) is 296°. Due to the influence of the Qiyueshan fault, the late arc-shaped structure is divided into two stages, the late K1 phase(the first period of arc structure in the late Yanshan), and K2(the second period of arc structure in the late Yanshan). Taking the Daba Mountain, Central Guizhou and Huangling uplifts as restraining points, the western Hunan and Hubei formed an arc structure from the southeast to the northeast with construction trace deflected from SN to NE, the direction of the maximum principal stress deflected nearly 86° and gradually extended to the Sichuan Basin until the Huaying Mountain fault. There is a certain difference in the impact intensity range of the two-stage arc structure. The northeast side of the study area is dominated by the mid-Yanshan arc structure, and the southwest side is dominated by the late Yanshan arc structure, resulting in differences of oil and gas reservoir between the northeast and southwest of the western Hunan and Hubei.