龙门山前缘关口断裂典型构造剖面的物理模拟实验及其变形主控因素研究  

Physical Simulation and Major Deformation-Controlling Factors of Typical Structural Sections for Guankou Fault in the Front of Longmen Mountains

作　　者：于福生[1] 张芳峰 杨长清[3] 李学良[1] 冯自成[1] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]内蒙古自治区第四地质矿产勘查开发院,内蒙古锡林浩特026000 [3]中国石化西南油气分公司勘探开发研究院,四川成都610081

出　　处：《大地构造与成矿学》2010年第2期147-158,共12页Geotectonica et Metallogenia

基　　金：中石化西南油气分公司勘探开发研究院"关口;彭县断裂带典型剖面构造形成过程物理模拟实验研究";国家自然科学基金项目(40972091)资助

摘　　要：关口断裂位于龙门山褶皱-冲断带前缘,根据构造线走向和典型地震剖面构造变形样式可划分出北、中、南三段。北段走向为北东50°,构造变形模式总体为不整合面所限制的基底卷入式前展型逆冲叠瓦式构造组合;中段走向为北东30°,构造变形模式为双滑脱层所控制的分层滑脱断层垂向叠加组合;南段走向为北东30°,变形模式为二叠系内滑脱层所控制的箱状背冲式构造组合。构造变形过程主要经历了印支晚期、燕山期、喜马拉雅期三个阶段。物理模拟实验证实北段变形的主控因素为斜向挤压(NW300°)和须家河组四段底部发育的高黏度滑脱层;中段变形的主控因素为正向挤压和双滑脱层的垂向叠置;南段变形的主控因素为正向挤压和二叠系内部低黏度厚层滑脱层的均匀分布。利用剖面模拟实验结果估算出的关口断裂不同构造段不同时期挤压构造变形强度(缩短率)不同,总缩短率表现为中段最大(39.63%),南段次之(34.93%),北段最小(32.72%)。印支期缩短率与总缩短率特征相似,中段为28.79%,南段为19.88%,北段为14.68%,而燕山期缩短率却表现为北段最大(18.04%),南段次之(15.05%),中段最小(10.84%)。The Guankou fault that locates in the front of Longmen mountains fold-thrust belt can be divided into three segments according to its structural trend and typical deformation styles. The general structural mode in the northern part which strikes in NE50° belongs to an imbricate thrust involved basement structure forward propagation restricted by unconformity interface. The general structural mode in the middle part which strikes in NE30° belongs to a superimposed decollement structure controlled by double detachment beds. The structural mode in the southern segment which strikes in NE30° belongs to a box fold-thrust structure. Tectonic evolution consists of three epoches：late Indosinian,Yanshanian and Himalayanian. Physical simulation results suggest that major factors controlling deformation in the north are oblique compression and high viscosity detachment beds which located at the fourth section of the Xujiahe Formation. Major factors controlling deformation in the middle part is contributed to the double detachment beds and vertical compression. Lower viscosity detachment bed in the Permian System and vertical compression can be responsible for the southern deformation. Deformation intensity estimated by simulation results in different segments and times is different. General shrinkage ratios of the north,middle and south are 32.72%,39.63% and 34.93%,respectively. Shrinkage ratios of the north,middle and south are 14.68%,28.79% and 19.88%,respectively in Indosinian epoch. However,shrinkage ratios of the north,middle and south in Yanshan epoch are 18.04%,10.84% and 15.05%,respectively.

关 键 词：龙门山前缘 关口断裂 彭县断裂 变形特征 物理模拟 

分 类 号：P542[天文地球—构造地质学]