中国中西部褶皱冲断带构造变形机制与结构模型

基于复杂构造解析和实验模拟研究,揭示了中西部前陆褶皱冲断构造带主要表现为受侧向挤压形成的滑脱冲断构造变形过程和结构样式;明确了单层滑脱挤压冲断构造变形存在临界增生和非临界增生两种变形机制,发育脆性拆离型、塑性滑移型和黏性流动型3种作用类型,并受滑脱层强度、地层厚度、底部边界和外动力过程等4种主要因素影响。复杂冲断构造带基本上表现为受多层单滑脱作用控制形成的垂向叠置组合结构,本文提出了复杂滑脱冲断变形结构的可分解性以及受不同性质的滑脱层组合控制形成特征结构模式,并揭示了前陆冲断带前缘多滑脱构造变形结构中由浅层向深层逐渐发育的变形时序;建立了中西部再生前陆冲断带结构模型、构造单元以及基本构造类型;并基于前陆盆地多阶段构造演化过程以及晚期的隆升剥蚀-沉降沉积过程,提出了中西部两种类型冲断带的控油气作用及其勘探领域。

Deformation mechanisms and structural models of the fold-thrust belts of central and western China

Based on complex structure interpretation and analogue modeling, we reveal that under lateral tectonic compression the fold-thrust belts of central and western China develop multi-layer detachments with varying deformation styles. For the contractional structural deformation with single basal detachment, there are two types of structural propagation mechanisms—critical and non-critical accretion, and three types of end-member deformation behaviors—brittle detachment, ductile sliding and viscous flow. And there are four main factors influencing the deformation processes and structural styles: detachment strength, strata composition, pre-existing basal structures and external dynamic processes. The fold-thrust belt developed a vertically superimposed composite structure controlled by multi-layer detachments, and we consider the complex slip-thrust regime can be disassembled vertically into various characteristic deformation layers controlled by different basal detachments. In addition, we show that the frontal foreland thrust belt forms multi-detachment structures from shallow to deep in deformation time sequence. Finally, a structural model of rejuvenated foreland thrust belts of the central and western China is constructed, along with the underlying deformation mechanisms, structural units and basic structural types. Based on the multi-stage tectonic evolutionary processes of the foreland basins and the Cenozoic basin-mountain coupling features, we present two types of hydrocarbon-rich thrust belts with different prospecting targets.