川东南马尾状褶皱带特征与形成机制的物理模拟

Analogue Modeling of Feature and Formation Mechanism of Horsetail-Shaped Fold Belt in Southeast Sichuan Basin,South China

川东南地区是我国南方重要的天然气探区,气藏分布受与该区的褶皱带构造演化密切相关.该区褶皱带呈现马尾状平面构造样式,对于这种特殊褶皱样式的形成机制存在不同的观点.构造物理模拟是研究构造形成机制的有效手段.为此,笔者在对该区马尾状褶皱特征详细分析的基础上,设计了5组模型,分别考虑边界几何形态、地层流变学结构、韧性层粘度和基底摩擦系数等4个因素,对该褶皱带的形成机制开展系统研究.结果表明:(1)该区马尾状褶皱带的形成与川东华蓥山断裂和齐岳山边界断裂形态关系密切;(2)脆/韧性地层厚度比和脆性层的厚度差对褶皱波长和样式具有重要控制作用;(3)适当的基底摩擦力是形成马尾状褶皱带的重要条件;(4)四川盆地内部、川东地区和湘鄂西地区基底流变学强度差异对该区马尾状褶皱带也具有重要影响.

The Southeast Sichuan area is one of important natural gas exploration areas in the southern China,and the distribution of gas reservoirs is closely related with the tectonic evolution of the fold belt,which shows horsetail-shaped planar pattern,with formation mechanism still in dispute.Analogue modeling is an effective method for the study of the structural formation mechanism.Based on the detailed analysis of the structural characteristics of the horsetail-shaped fold belt in this area,we designed five sets of models,considering four factors including boundary geometry,stratigraphic rheological structure,ductile layer viscosity and base friction coefficient,to conduct a systematic study on its formation mechanism.The results show that：（1）The formation of the horsetail-shaped fold belt is closely related to the shapes of Huayingshan fault and Qiyueshan boundary fault in the East Sichuan;（2）The ratio of brittle/ductile strata and thickness difference of the brittle layers have important controls on the wavelength and pattern of the folds;（3）The appropriate base friction is an important condition for the formation of the horsetail-shaped folds;（4）The difference of the basal rheological strength between the Sichuan basin,the East Sichuan and the West Hunan-Hubei may also have an important effect on the formation of the horsetail-shaped fold belt.