藏东小昌都-灯昌断裂空间展布及其构造变形特征研究

Study on Spatial Distribution and Structural Deformation Characteristics of Xiaochangdu-Dengchang Fault in Eastern Tibet

古学水电站为澜沧江上游西藏段河段水电规划推荐的第7级电站,发电效益显著。小昌都-灯昌断裂为藏东芒康古学水电站外围的一条断裂构造,因其位置特殊,分析其空间展布与构造变形特征对水电站工程建设具有重要参考意义。文章通过对断裂进行野外大比例尺调查、断裂带露头剖面构造解析等,结果显示断层表现为NW(下)盘上升、SE(上)盘下降的正断层性质;断裂空间展布上在距澜沧江约2.5km处(竹卡断裂之东约0.5km)即未见其出露而终止,表明其在地表未切割竹卡断裂而延伸至澜沧江边;断层破碎带中以挤压变形为主,结合断层泥测年结果 177.61ka±19.54ka、216.15ka±18.37ka、254.51ka±27.99ka,显示断裂最新活动时间为中更新世,但局部可见断层逆冲至上覆残坡积层之上,疑似断层具有活动性。

Guxue hydropower station is the 7th grade power station recommended by the hydropower planning of Tibet section of the upper reaches of Lancang River,and the power generation benefit is remarkable.Xiaocamdu-Dengchang fault is a fault structure outside Mangkang ancient Hydropower station in eastern Tibet.Because of its special location,spatial distribution and structural deformation characteristics are of great reference significance for hydropower station construction.In this paper,large scale field investigation of the fault and analysis of the outcrop section of the fault zone are carried out.The results show that the NW(foot)wall is rising and SE(handing)wall is falling,suggesting the normal fault.At a distance of about 2.5km from the Lancang River(about 0.5km east of the Zhuka fault),it was terminated without being seen to emerge,indicating that it extended to the Lancang River without cutting the Zhuka fault on the surface.The fault fracture zone is dominated by extrusion deformation.Combined with the fault gout dating results of 177.61ka±19.54ka,216.15ka±18.37ka,254.51ka±27.99ka,it is indicated that the latest fault activity time is the Middle Pleistocene.But the fault thrust can be seen on the upper overlying Qedl,and the fault is suspected to be active.