【作者】 刘战庆；

【导师】 裴先治；

【作者基本信息】 长安大学 ， 构造地质学， 2008， 硕士

【摘要】 陕南镇巴-紫阳地区处于上扬子地块北缘与南秦岭的巴山弧形逆冲推覆系叠合部位,东西横跨扬子板块和秦岭造山带及处于两者之间的勉略缝合带三大构造单元,该区经历了长期多体制的地质构造演化,形成了复杂的构造物质组成,是研究秦岭造山带发展演化的重要场所。本文在宏观掌握扬子地块和南秦岭造山带及邻区最新研究成果和研究进展基础上,重点收集区域有关地层学、岩石学、构造地质学及其测年数据等方面的研究成果,对比分析研究区各个地层小区地层,对该区的地质构造的几何形态、结构组合、以及运动学与区域构造背景方面匹配,来解剖陕南镇巴-紫阳地区的构造特征,进而对其构造演化进行分析。在系统总结前人研究成果的基础上,通过野外调研分析及室内的整理,对于镇巴-紫阳地区构造特征及构造演化得出以下几点结论和认识。1.陕南镇巴-紫阳地区构造特征主要表现为:①断裂构造表现为高角度逆冲推覆性质,组合呈叠瓦扇式逆冲推覆构造系;②逆冲推覆构造系中的褶皱主要表现为东倾西倒的同斜倒转紧闭形态;③构造叠加特征明显,褶皱、断裂表现为斜向逆冲推覆兼右行走滑性质,米仓山地层小区内的褶皱具有明显的南北向同东西向的叠加复合特征④该区逆冲推覆构造扩展方式表现为由东向西的前展式。2.现今陕南镇巴-紫阳地区构造是经历了多期多体制的地质构造演化,形成了复杂的构造物质组成面貌。早古生代北大巴山地区处于伸展构造环境形成一系列同倾向正断层组成的大型犁式的堑-垒构造,并发育同沉积生长断层;晚古生代褚河地层小区发生伸展作用形成深海裂谷;印支期构造反转,由伸展构造环境向挤压构造环境转换,发生陆缘碰撞造山作用,形成逆冲推覆构造;燕山期整个大巴山逆冲推覆系向南西方向大规模的逆冲推覆陆内造山,形成了现今构造格局;喜玛拉雅期逆冲推覆构造又开始活跃,使前期的逆冲推覆向前陆盆地方向继续扩展。更多还原

【Abstract】 Zhenba - Ziyang area in sorth Shaanxi was an essential spot for Qinling orogenic belt study, which was located at superposition of the northwest margins of Yangtze block and obduction zone of arcuate structure of Daba mountains of south Qinling, and overlapped among three tectonic unions of Qinling orogenic belt, Mianlve tectonic belt and Yangtze block from east to west,and experienced a long-term and multistage tectonic evolution,eventually, formed the sophisticated structure of the material constitutes.Based on the new research findings and progress of the south Qinling orogen belt and the northwest margins of Yangtze block in general,especially the achievements of stratigraphy,petrology,structural geology and isotopic chronological data et al.,and analysis of each stratum of study area,together with coordination of the area in morphologic geometry,structural assemblage,movement study and regional structural background,the structural feature of Zhenba - Ziyang area in sorth Shaanxi was analyzed systematically,and its tectonic evolution was also analyzed in the paper.After concluding the research achievements of predecessors, field observations and indoor treatment systematically,some pieces of conclusions and recognitions about structural feature and tectonic evolution in Zhenba - Ziyang area were obtained as follows;1. The structural characteristics in Zhenba - Ziyang area in sorth Shaanxi were mainly featured as follows:①The representations of tectonic faults were a large-scale angle thrust and a assemblage of fan-imbricate thrust in structure system;②The axial plane of folds in the thrust-nappes tectonic system mainly displayed east-inclined and its limbs were homoclinal and were reverse closed.③The structure superimposition characteristic was obvious that the folds and faults displayed for diagonal thrust pushes and right-lateral-slip.And there was a conspicuous superimposition compound characteristic between N-S direction and W-E direction in the Micang Stratum plot.④The pattern of thrust-nappe tectonic expansion in this area was forward propagation from east to west.2. Experienced multistage and multi-mechanism tectonic evolution, the complex structure material composition appearance at present of Zhenba - Ziyang area in sorth Shaanxi had formed. Before Indo-Chinese epoch, the area mainly performed for extensional function and structural environment, and the structure in Chu-River Stratum plot on the eastward of Mianlve-belt and north Daba Mountain area was characterized by large-scale plow-like horst-graben tectonics which consisted of a series of normal faults in the same tendency, companying with synchronous deposited faults. Entered Indo-Chinese epoch, the whole north margin of Yangtze tectonic plate subducted downward to the Qinling tectonic plate from south to north, and the latter thrust upward to the former and formed structural reverse. Meanwhile, the tectonic background transformed from normal fault state under extentional condition to thrust state under compressional condition, and epicontinental collision orogenesis occurred.In Yanshan orogeny, the whole thrust system of Daba mountain obducted toward southwest in a large-scale and formed intracontinental orogenic belt, in which graded progress the major characteristics of present tectonic framework in the area had formed.The whole thrust system became reactive in Himalaya orogeny, which enabled preceding thrust to advanced toward Sichuan Basin continually.更多还原