岩石磁组构在断裂变形性状与期次研究中的应用——以广西博白-合浦断裂为例

APPLICATION OF ROCK MAGNETIC FABRIC IN THE STUDY OF FAULT ——EXAMPLIFIED BY THE BOBAI-HEPU FAULT

岩石磁化率椭球体的三个轴与应变椭球体的三个轴方向相平行 ,并具有一定的共构关系。变形岩石的磁组构参数 P、T、F、L以及磁化率椭球体主张量方向等可以用来定量地表征岩石变形的性状及期次。本文通过实测和计算 2 7个样品的磁组构参数 ,研究了博白 -合浦断裂带的变形性状与期次 ,结果表明 :博白 -合浦断裂带大致经历了三期构造变形作用 ,不同时期具不同性质的构造变形。变形性状分别表现为韧性、韧 -脆性及脆性变形 ,应变行为分别表现为平面、非平面和线性应变。

Many studies have proved that the role of magnetic ellipsoid of rocks is equal to that of tectonic strain ellipsoid. The parameters of magnetic fabric, such as P, T, F and L, can be used to describe the behaviors and periods of tectonic deformation. The features and periods of tectonic deformation of the Bobai Hepu fault are studied with rock magnetic fabric in this paper. The research shows that the anisotropy parameters (P) of the Bobai Hepu fault can be divided into three parts which stand for three types of tectonic deformation: brittle (P≤0.35),ductile brittle (0.40≤P≤0.60) and ductile (P≥1.0). The shape factor of magnetic ellipsoid (T) shows that the fault has two kinds of magnetic ellipsoids which are the compression (T<0 )and stretch (T>0). The relation between magnetic foliation (F) and lineation (L) shows that the fault has three types of strain which are plane, non plane and linear strains. The trends of the principal axes of magnetic ellipsoid show that the fault has been acted by the stresses with different direction in varied periods and has different shear trends. The final result of the present paper is that the Bobai Hepu fault suffered three period tectonic deformation with varied deformation mechanisms.