六盘山构造带南段陇县—宝鸡断裂带晚第四纪活动特征及其构造意义

As the tectonic boundary zone generated by the compression deformation between the northeastern margin of Tibetan Plateau and Ordos block, the Liupanshan tectonic zone is the most forefront area where the Tibetan Plateau uplifting and expanding. The deformation and neotectonic evolution, especially the further study on Late Quaternary characteristics of the relevant faults within the Liupanshan tectonic zone not only provides the most direct geological restraint for the setting up of regional tectonic deformation patterns, but also makes a great sense to the discussion of the growth pattern, beginning period and mechanism that Tibetan Plateau forward to the inner continent. We aim the study intertest at the Longxian-Baoji fault in the southern segment of Liupanshan tectonic zone. With the principles and methods of morphotectonics, on the basis of the interpretation of high-resolution remote sensing images and the analysis of DEM(Digital Elevation Model)data, intensive study focusing on the strike slip and normal characteristics of the Longxian-Baoji fault will be carried out.The Late Quaternary activity parameters will be obtained through detailed field investigation and mapping along the fault combining with the high precision surveying and Quaternary dating. Reveal the vital function and its tectonic significance that Longxian-Baoji fault performed in shifting and transforming of the tectonic deformation in northeastern margin of the Tibetan Plateau. Then, integrating with the regional active tectonics and geophysical material, the tectonic deformation model will be build. Growth pattern and its possible dynamic mechanism in the newest forefront area of Tibetan Plateau will be discussed also.

六盘山构造带是青藏高原东北缘和鄂尔多斯地块西南缘挤压构造的边界带，是青藏高原隆升和扩展的最前缘，其形成及新构造演化，特别是构造带相关断裂晚第四纪活动特征的深入研究，不仅能为区域构造变形模式的建立提供最基本的地质约束，也对进一步探讨青藏高原向大陆内部生长扩展的方式、时代和机理等问题具有十分重要的科学意义。本课题选择六盘山构造带南段的陇县—宝鸡断裂带为研究对象，运用构造地貌学基本原理与方法，在高分辨率遥感影像解译和DEM数据分析的基础上，沿断裂开展详细的地质地貌调查和填图，结合高精度地貌测量和第四纪测年，重点对陇县—宝鸡断裂带的走滑及正断特征进行深入研究并获取断裂晚第四纪活动性参数，揭示陇县—宝鸡断裂带在青藏高原东北缘构造变形迁移和转换过程中的重要作用及其构造意义。在以上工作的基础上，结合区域活动构造和地球物理资料，建立研究区构造变形模式，探讨青藏高原最新前缘部位的扩展方式和可能的动力学机制。

六盘山构造带是青藏高原东北缘重要的活动构造边界带，其西部为青藏高原的陇西块体，其东部为构造稳定的鄂尔多斯块体。六盘山构造带北部和南部的构造样式具有显著的差异性，主要表现在活动断裂的性质及运动学特征等方面。有关断裂晚第四纪活动特征的深入研究，不仅能为区域构造变形模式的建立提供最基本的地质约束，也对进一步探讨青藏高原向大陆内部生长扩展的方式、时代和机理等问题具有十分重要的科学意义。本课题在高分辨率遥感影像和DEM数据分析的基础上，对六盘山构造带的主要活动断裂开展了详细的地质地貌调查，并开展了典型断错地貌精细测量、古地震探槽开挖和年代学样品测试等工作。重点对陇县—宝鸡断裂带中最重要的陇县-岐山-马召断裂晚第四纪活动特征进行了研究，获得了其精细的几何展布及分段活动特征。对六盘山构造带北段和南段交接过渡部位的活动断裂进行了详细调查，发现了陇县盆地西南缘正断层存在的确切证据，建立了六盘山东麓逆断裂和陇县-宝鸡断裂带之间的构造转换关系，提出了六盘山构造带一种可能的变形模式。