后挡形态对褶皱冲断带平面展布的影响——来自平面砂箱模拟试验的启示

Influences of the Backstop Shape on the Plane Distributions of Fold-fault Zones——Insight from Plane Sandbox Experiments

近几年的研究工作表明,边界几何条件是影响盆地构造形成最主要的因素,然而,研究主要集中在剖面构造模拟方面,平面构造模拟方面尚处于起步阶段。针对前人研究的不足,根据相似性原理,通过4组构造物理砂箱模拟试验的对比来模拟后挡形态对褶皱冲断带平面展布的影响,得出以下认识:后挡的形态不同,产生的冲断带边界会有差别;后挡的顶角越小,形成断层带的弧度越大,弯曲程度越大,总体上来说两者的平面形态具有较好的相似性;后挡的角度不同,形成的区域大断层的数量不同,后挡的角度越大,应力分布越均匀,砂层在横向上的变形程度越接近,越容易形成区域大断层;通过应力场分析也证实了利用应力场来预测褶皱冲断带的平面展布是正确的。试验属理想模型,是对实际问题的抽象研究,可为实际地质问题的分析研究提供启示。

Recent researches indicated that boundary geometric condition were the most important influential element in the formation of basin tectonics,however,the researches mainly focused on the section structural modeling,while plane structural modeling was still at the preliminary stage.Aiming at the shortcomings of our predecessors' studies and based on the analog principle,the contrasts of four groups of structural modeling experiments were used to study the influence of the backstop shape on the plane distributions of fold-fault zones.The result shows that difference of backstop shape produces different boundaries of faulting zones;the smaller the backstop angle is,the larger the radians of the fault zone is,the higher the curvature would be,totally the shape of the both is similar on the plane;different angles of backstop produce different numbers of regional faults,the larger the backstop angle is,the more even the stress distribution is,the closer the shape in lateral deformation of the sand layers is,the easier the formation of the regional faults would be.It is proven to be correct for predicting the plane distributions of fold-fault zones by the analysis of the stress field.This experiment is an ideal model and an abstraction of the real problems,also it can provide an inspiration for the analysis of geological issues.