西昆仑山北麓新生代前陆褶皱冲断带构造特征与变形机制定量研究

The West Kunlun orogenic belt and the adjacent sedimentary basin are critical for the study on the Cenozoic structural deformation. The continuous process of the uplift and expansion of the mountain, the structural deformation in the piedmont, and the migration of the forland basin is the intra-continental tectonic response of the collision between India and Euroasia plates. It is highly significant for the understanding on the mechanism and remote effect of India and Euroasia plate collision. The Cenozoic fold-and-thrust belts in the northern piedmont of western Kunlun Shan are new strctures with abundant structural features, and are well preserved. They are ideal subjects for the systematic study of the deformation patterns and deformation mechanism of fold-and-thrust belts. We propose to do a quantitative research on the Cenozoic structural features, the evolution of the deformation, and its controlling factors. And we are going to discuss the relationship between the uplift and expansion of the mountain, the structural deformation in the piedmont, and the migration of the foreland basin. Results from this project will provide geological evidence and structural insights for the research on the dynamics of the West Kunlun Shan mountain and basin system. In addition, results from this project will provide theory directions for the oil and gas exploration in the fold-and-thrust belts in the northern piedmont of Western Kunlun Shan and other similar regions.

西昆仑造山带及其相邻的沉积盆地是研究新生代构造变形的关键地区之一。本区晚新生代以来持续发生的山脉隆升扩展、山麓构造变形、山前盆地迁移是印度板块与欧亚大陆碰撞在陆内腹地的构造响应,对理解印度-欧亚板块碰撞机制及其远程效应具有深刻意义。西昆仑山北麓新生代褶皱冲断带形成时代新，构造地质现象丰富，保存完整，是开展褶皱冲断构造系统变形样式与变形机制研究的理想场所。本项目拟通过地表构造调查、地球物理资料综合解释、结合构造物理模拟实验和离散元数值模拟，精细解剖、定量研究西昆仑山北麓不同区段的新生代构造特征、变形时空分布规律及其控制因素，探讨新生代西昆仑山山体隆升扩展-山麓构造变形-山前盆地迁移的相互关系，为西昆仑山盆山体系动力学机制研究提供地质证据和构造信息，同时为本区及其他前陆褶皱冲断带的油气勘探与开发提供理论指导。

本项目针对西昆仑山山脉隆升-构造变形-山前盆地沉降，以山前褶皱冲断带为切入点，拟通过精细地表构造调查和地震资料综合解释，结合构造物理模拟实验和离散元数值模拟，开展西昆仑山北麓新生代构造特征和时空分布及区域构造剖面模拟，揭示了西昆仑山前麓新生代构造变形特征及其控制因素，为西昆仑山盆山体系动力学机制研究提供地质证据和构造信息，同时为西昆仑山及其他前陆褶皱冲断带的油气勘探与开发提供理论指导与地质模型。通过物理模拟的方法，我们模拟了塔西南柯东构造带的形成和演化过程。实验结果表明，区域挤压作用力和构造剥蚀作用是该区构造形变的主要控制因素。同时，侏罗系煤层和古近系膏盐岩是该区区域性分布的两套重要的弱性地层沉积，对柯东构造带变形具有控制影响。侏罗系至古近系滑脱层调节了上下地层之间的变形差异，下覆基底发育了大规模的逆冲推覆构造变形，逆冲断层的前缘沿侏罗系煤系地层滑脱，往北盆地方向基底变形较弱；与基底构造变形不协调的是，古近系之上地层发育的反冲滑脱构造变形。基于构造物理模拟及数值模拟结果，我们认为古近系阿尔塔什组膏岩层并非作为独立滑脱层在起作用，它与其下伏侏罗系煤系地层耦合成一复合滑脱体系。该复合滑脱体系控制了柯东构造带深浅构造脱耦与差异性演化。通过系统的构造物理模拟及离散元数值模拟实验，我们研究了岩层强度、剥蚀作用、同构造沉积等因素褶皱冲断构造形成与演化的控制作用，结果显示滑脱层的数量、分布范围、及其相对强度是影响盆山体系构造横向分带、纵向分层的关键因素，对盆山体系的构造样式、变形传播、油气成藏具有重要的影响。