【摘要】 沿龙门山南段冲断前锋带飞仙关断层传播褶皱剖面钻取了270个磁组构定向岩芯样品,对其进行了磁性矿物与磁组构分析。通过等温剩磁和三轴热退磁实验确定了样品中的主要载磁矿物为赤铁矿。磁组构测试结果显示27个采样点的磁组构为中间组构与构造组构两种类型。通过对各点磁组构特征及各项磁组构参数进行详细分析,再结合断层传播褶皱运动学模型,得出断层传播褶皱形成过程中岩石应变及磁组构演化:断层扩展前的平行层缩短作用把原始的沉积组构改造成为中间组构;在断层扩展过程中,两翼地层的旋转抬升产生的简单剪切作用对地层磁化率各向异性产生影响,使得校正的磁化率各向异性度Pj值局部升高,以及在剪切变形强烈的区域形成构造磁组构。更多还原

【Abstract】 Along Feixianguan fault-propagation fold cross-section in the southern Longmenshan front, 270 oriented specimens were drilled to conduct the analysis of magnetic minerals and anisotropy of magnetic susceptibility (AMS). We find that hematite is the main magnetic carrier mineral according to isothermal remanent magnetization acquisition and demagnetization of three orthogonal isothermal remanent magnetization. The AMS results show two types of magnetic fabrics: intermediate magnetic fabric and tectonic magnetic fabric. Based on the kinematic model of fault-propagation fold and distribution features of magnetic fabrics, we deduce the evolution of magnetic fabrics through the development of fault-propagation fold: primary sedimentary fabrics were transformed into intermediate fabrics by the pre-folding layer parallel shortening; during the propagation of fault, simple shear caused by limbs’ rotation and lift affects the AMS at limbs, which make Pj rise locally within limbs, and structural fabric appears in strong deformation area.更多还原