湖北省郧县红岩背地区剪切褶皱构造解析

THE STRUCTURAL ANALYSIS OF THE SHEAR FOLD IN HONGYANBEI AREA,YUN COUNTY,HUBEI PROVINCE

剪切褶皱及其所赖以形成的滑动面──轴面劈理的成因是长期以来颇有争议的问题。本文在对剪切褶皱详细的宏微观观察的基础上，系统论述了滑动面所具有的挤压和剪切的双重力学性质，并首次运用递进单剪变形理论解释劈理的成因，指出劈理作为一个物质面，其初始和最终的发育均垂直于应变椭球体的最小应变主方向，而在变形过程中二者发生斜交，从而很好的解释了劈理的双重力学性质。在此基础上本文进一步探讨了剪切褶皱的形成模式，把剪切褶皱的形成分为六个主要阶段。该模式指出剪切褶皱并。是单纯的与层面斜交的剪切作用产物，而是在纵弯褶皱作用的基础上形成的。纵弯褶皱作用形成初始褶皱，在褶皱转折端部位由于压扁作用形成与褶皱轴面平行的劈理，而在褶皱翼部则发生递进单剪变形而形成与轴面斜交的劈理，这些劈理在变形后期由于挤压而逐渐转至与轴面平行。岩层沿轴面劈理发生依次错动形成剪切褶皱。因此，剪切褶皱是纵弯和剪切两种机制联合作用的产物。

The origin of shear fold and its slip pine axial plane cleavage has been being a control-versial problem for a long time. Based on the detaily macro and micro observations of the shear fold, this article discusses systematicly the double mechanical natures of both shear and compression for ship plane and firstly explains its origin with the theory of progressive simple shear deformation,points out that as a meterial plane,at the beginning and the end of the defomration,cleavage is perpendicular to the minimum principle direction of strain,but during the course of the deformation they are oblilque to each other,thus explains, well the double mechanical natures of cleavage. Based on these this article dis-cusses furtherly the formation of shear fold, divding the development of shear fold into six main stages.In this pattern shear fold is thought to be not a simple preduction of sole sliding oblique to bed plane but is formed based on buckling,An original fold is formed by buckling and at the hinge area of which cleavage parallel to the axial plane is formed by flattening, while at the limbs cleavages oblique to the axial plane are formed by progressive simple shear deformation,they are rotated by press and at last approximately parallel to the axial plane .Rock formation’s sliding along the axial plane cleavages forms shear fold eventualy. Hence,shear fold is a combined production of both buckling and shear.