Abstract:

The sand veins in Yuanmou fault zone have been investigated in the work, and its tectonic implications has been defined. The result shows that the sand veins generally develop in the surface or sub-surface rock straum in the middle-north segment of Yuanmou fault, and extends parallelly along the fault with larger dip angles. In addition, the patterns and structures of the sand veins and its relationship of the host rocks show that the sand veins were filled with the stretchable fracture from the overlying strata as the result of the sand liquefaction from the main fault plane or secondary fault pane which were connected with Yuanmou fault was intensively active, or due to the strong earthquake. Moreover, the thermoluminescence (TL) and optically stimulated luminescence (OSL) dating show that the sand veins were formed about 7 kaBP, indicating a intensive activity of Yuanmou fault during the Late Quaternary.

Key words: Yuanmou fault, sand vein, fault activity, sand liquefaction, accessory

摘要：

依据元谋断裂带砂脉发育的层位、成份、形态、围岩变形特征、区域构造背景和古气候环境, 以及断裂带晚第四纪活动特征, 结合释光年代学测试结果, 讨论砂脉的成因机理及其与断裂带的关系。结果表明, 元谋断裂带地表或近地表发育的砂脉较多, 产状近直立, 延伸较长, 沿断裂中?北段构造面平行展布。综合分析砂脉形态、内部结构以及与围岩和断层的空间关系, 揭示砂脉的形成应是断裂带强烈运动或地震活动引起的断层带上、次级断裂面上以及构造面附近局部节理面砂土液化的结果, 或为伸展构造面裂隙充填物, 且可能为同一期地质事件所为, 形成时间约为7 kaBP。这些砂脉构造对断裂活动的时限具有重要指示意义, 是元谋断裂晚第四纪一次强烈活动的伴生产物。

关键词: 元谋断裂带, 砂脉, 断裂活动, 砂土液化, 伴生产物