利用拉分盆地和错断河流阶地定量评估康西瓦断裂晚第四纪平均左旋走滑速率  

APPLICATION OF THE PULL-APART BASIN AND OFFSET RIVER TERRACE TO STUDY THE LATE QUATERNARY LEFT-LATERAL SLIP RATE OF THE KANGXIWAR FAULT

作　　者：龚志军[1] 张志亮 祝民强 彭花明[1] 付翔 吴郴 Gong Zhijun;Zhang Zhiliang;Zhu Minqiang;Peng Huaming;Fu Xiang;Wu Chen(School of Earth Sciences, East China University of Technology, Nanchang 330013, Jiangxi;Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013 [2]中国科学院地质与地球物理研究所、中国科学院新生代地质与环境重点实验室,北京100029

出　　处：《第四纪研究》2018年第3期659-667,共9页Quaternary Sciences

基　　金：国家自然科学基金青年项目（批准号：41402162）、国家国防科技工业局科工二司（2014）1587号项目、中国科学院战略性先导科技专项项目（批准号：XDB03020500）和国家自然科学基金项目（批准号：41290251和41272203）共同资助

摘　　要：康西瓦断裂为青藏高原西北缘的一条大型左旋走滑断裂.目前,不同学者对康西瓦断裂晚第四纪的平均走滑速率仍存在较大争议.文章以青藏高原西北缘喀拉喀什河谷段一处冲洪积扇上发育的一个小型拉分盆地以及该冲洪积扇上发育的一个错断河流阶地为研究对象,基于拉分盆地演化的两种简单模式,分别利用拉分盆地的长边和斜边限定对应冲洪积扇的水平位错位量和错位量的上限值,而通过光释光定年技术约束该冲洪积扇的形成年代,结合相关数据,分别估算出康西瓦断裂晚第四纪以来的平均左旋走滑速率为小于或等于8.6±1.0 mm/a和小于约12.4 mm/a.与此同时,利用该冲洪积扇上发育的错断河流阶地的水平位错和对应阶地的放弃年龄,估算出康西瓦断裂晚第四纪以来的平均左旋走滑速率为8.4±1.0 mm/a.The Kangxiwar Fault is one of the largest left-lateral strike-slip faults at the rim of northwestern Tibetan Plateau.However,the Late Quaternary slip rate of the Kangxiwar Fault is still in debates.In this study,a small pull-apart basin and an offset river terrace across the Kangxiwar Fault were identified near the Xinjiang-Tibet highway milepost 415 km.Both the small pull-apart basin and offset river terrace were formed within an alluvial fan in the Karakax valley due to the Late Quaternary faulting along the Kangxiwar Fault.For the pull-apart basin,two models were assumed.In the first model of the pull-apart basin,the width of the pull-apart basin did not increase significantly and remained constant during its evolution.Thus,the long side of the pull-apart basin （450±45 m）can be used as the offset of the alluvial fan.An optically stimulated luminescence （OSL） sample （KXW-OSL-2） was collected at the bottom of terrace riser（T2/T1）（36°14′ 20.O″N,78°32′ 37.2″E）,and the corresponding age was used to constrain the youngest age of the alluvial fan.The OSL dating results show that the alluvial fan formed at or before 52.4±3.4 ka.Thus,the average left-lateral slip rate of the Kangxiwar Fault was estimated at less or equal to 8.6±1.0 mm/a.In the second model of the pull-apart basin,both the width and length increased during the evolution of the pull-apart basin.In this case,the hypotenuse（650±65 m）was used to estimate the maximum offset of the alluvial fan.Correspondingly,together with the OSL age of the alluvial fan,the average left-lateral slip rate of the Kangxiwar Fault was estimated at less than ca.12.4 mm/a.For the older terrace within the alluvial fan,another OSL sample（KXW-OSL-1） was collected at the terrace tread of T2,and the results show that the terrace was abandoned at 30.9±2.1 ka.If the terrace riser was used as the offset marker,the horizontal displacement of the terrace was estimated at 260±26 m.Together with the abandoned age of the river terrace within the all

关 键 词：康西瓦断裂 拉分盆地 释光定年 晚第四纪 走滑速率 

分 类 号：P546[天文地球—构造地质学] P597.3[天文地球—地质学]