沁水盆地东部构造演化特征及构造物理模拟

沁水盆地东部煤层气勘探潜力巨大,构造演化特征相对独特。依据野外地质踏勘资料,对沁水盆地东部的构造特征进行系统研究。利用平衡剖面回剥方法,定量分析典型剖面的运动学参数。在研究区构造几何学、运动学特征分析基础上,基于构造物理模拟实验,再现了沁水盆地东部的构造演化过程,从而对研究区构造演化取得了新的认识。研究表明,沁水盆地东部依次经历了弱挤压-强挤压-弱伸展-强伸展的演化过程,可将其构造演化划分为板块拼合盖层沉积(J_1前)、陆内强烈挤压变形(J_2～J_3)、微弱伸展活化(K-E)和陆内伸展裂谷(N-Q)4个阶段。此构造演化对沁水盆地东部煤层气的聚集与勘探开发具有重要影响,其动力来源主要受控于区域构造应力场的重大转变。早侏罗世以前,板块碰撞拼合及印支运动的辐射将沁水盆地东部置于NNW-SSE向挤压应力场;中-晚侏罗世,研究区开始出现重要构造分异与转折,整体转向NW-SE向强挤压应力场,逆冲断裂雏形在此阶段形成;白垩纪-古近纪,区域应力场由NW-SE向挤压应力场转变为NW-SE向伸展应力场,研究区构造体制发生重大转折;21世纪以来,研究区进入陆内伸展改造,构造格局至此基本定型。

Structural characteristics and evolution of the eastern Qinshui Basin based on the tectonic physical simulation

The eastern part of Qinshui Basin has great potential for coal bed methane exploration and unique structural evolution. According to the field geological survey, the structural characteristics of the region are systematically studied. The kinematic parameters of typical sections are quantitatively analyzed by using the method of balanced section stripping. Based on the analysis of the structural geometry and kinematics characteristics of the study area, the tectonic evolution process of the eastern Qinshui Basin is reproduced by the tectonic physical simulation experiment, thus a new understanding of the tectonic evolution of the study area is obtained. The study shows that the eastern Qinshui Basin has undergone the evolution process of weak compression, strong compression, weak extension and strong extension in turn. Its tectonic evolution can be divided into four stages: plate assemblage cover deposition (before J1), intracontinental strong compression deformation (J2-J3), weak extension activation (K-E) and intracontinental extension rift (N-Q). The tectonic evolution has an important influence on coalbed methane accumulation and exploration, and the dynamic source is mainly controlled by the significant change of regional tectonic stress field. Before the early Jurassic, the region was in the NNW-SSE compressive stress field due to plate collision and assemblage, and the radiation of Indosinian movement. During the Middle-Late Jurassic, the study area turned to NW-SE compressive stress field with a strong structural differentiation and transition, and the rudiment of thrust faults formed in this stage. From Cretaceous to Paleogene, the regional stress field changed from NW-SE compressive stress field to NW-SE extensional stress field, and the tectonic system of the study area changed greatly. Since Neogene, the study area has entered the intracontinental extensional transformation and the tectonic pattern has been basically finalized.