秦岭沙沟街韧性剪切带的岩石磁学、磁组构和运动学涡度分析

发布时间：2018-11-06 08:26

【摘要】：秦岭商丹构造带内发育的晚三叠世沙沟街韧性剪切带蕴含大量地质信息,很好地记录了秦岭印支期碰撞造山过程。为了探究该剪切带的运动学特征及其动力学背景,在野外观测、显微构造分析的基础上,对其中发育的糜棱岩进行了磁组构和运动学涡度研究。岩石磁学和磁组构分析结果显示:样品的平均磁化率Km值总体较高,载磁矿物主要为磁铁矿等铁磁性矿物;磁化率各向异性度PJ值较大,表明构造变形较为强烈;形态参数T值多大于0,反映磁化率椭球体以扁球体为主;磁线、面理优势产状与野外观测到的矿物线、面理较为一致。结合磁组构、边界断层以及C面理产状,认为沙沟街韧性剪切带具有左行走滑挤压的运动学特征。运动学涡度Wk值及其分布特征表明,沙沟街剪切带中纯剪切作用所占的比重总体大于简单剪切作用,并且剪切带的核部应位于北界断层附近。综合分析认为,沙沟街韧性剪切带的运动学特征反映了总体斜向汇聚背景下的局部走滑挤压,与商丹带西段发育的同期韧性剪切带具有完全反向的运动学指向,这可能与碰撞导致的侧向挤出构造有关
[Abstract]:The late Triassic Shagou Street ductile shear zone developed in the Shangdan tectonic belt of Qinling contains a great deal of geological information which records the collision orogenic process of the Qinling Indosinian epoch. In order to study the kinematic characteristics and dynamic background of the shear zone, the magnetfabric and kinematic vorticity of mylonite developed in the shear zone were studied on the basis of field observation and microstructural analysis. The results of rock magnetics and magnetic fabric analysis show that the average magnetic susceptibility (Km) of the samples is generally high, the magnetization minerals are mainly ferromagnetic minerals such as magnetite, the anisotropy of magnetic susceptibility is large, which indicates that the tectonic deformation is relatively strong. The shape parameter T value is more than 0, which reflects that the flat sphere is the main body of magnetic susceptibility ellipsoid, and the magnetic line, the dominant occurrence of the surface texture is consistent with the mineral line observed in the field. Combined with magnetic fabric, boundary fault and C plane occurrence, it is considered that the ductile shear zone in Shagou Street has the kinematic characteristics of left strike-slip extrusion. The Wk value of kinematic vorticity and its distribution characteristics show that the proportion of pure shear in Shagou Street shear zone is larger than that of simple shear, and the core of shear zone should be located near the north boundary fault. It is concluded that the kinematic characteristics of the ductile shear zone in Shagou Street reflect the local strike-slip compression in the general oblique convergent background, and have a completely opposite kinematic direction with the same time ductile shear zone developed in the western section of the Shangdan belt. This may have something to do with the lateral extrusion structure caused by the collision.
【作者单位】：西北大学大陆动力学国家重点实验室;中国科学院地质与地球物理研究所;
【基金】：国家自然科学基金创新群体项目(41421002);面上基金项目(41672200) 西北大学大陆动力学国家重点实验室科技部专项经费(201210133、207010009)联合资助
【分类号】：P318.41;P542

【相似文献】