摘要
柴达木盆地是青藏高原北部面积最大、地层厚度超过10 km的新生代沉积盆地。通过揭示盆地内新生代地层保存的磁组构信息,可以重建区域构造应力方向,进而探讨青藏高原北部构造变形及其动力学机制。通过对柴达木盆地北缘路乐河新生代地层样品各方向磁化率进行测量,获得了1070个样品的磁组构信息,并对磁组构形态和相关参数进行分析。结果表明:柴达木盆地北缘路乐河剖面23.7~9.9 Ma地层的磁组构表现为初始变形磁组构,磁线理指示了挤压应力的方向,9.9~5.2 Ma地层的磁组构以沉积磁组构为特征,未记录到明显构造应力方向。利用磁偏角去除构造旋转的影响后,路乐河剖面沉积地层磁组构记录的挤压应力方向在不同的时段存在差异。23.7~18.1 Ma聚集在约25°方向,揭示柴达木盆地北缘早中新世遭受近SN向挤压应力;18.1~15.2 Ma挤压应力方向发生逆时针旋转,由约25°旋转至约-20°;15.2~9.9 Ma挤压应力方向发生顺时针旋转,由约-20°旋转至约20°。这些结果揭示柴达木盆地北缘挤压应力方向在中中新世先发生逆时针旋转(18.1~15.2 Ma),后发生顺时针旋转(15.2~9.9 Ma)。综合周边的构造格架及前人构造变形分析的相关结果认为,柴达木盆地北缘中中新世以来构造应力的旋转可能与东昆仑山和祁连山双向挤压应力的叠加紧密相关。
The Qaidam Basin is the largest Cenozoic sedimentary basin on the northern part of Qinghai-Xizang Plateau,with a stratum thickness exceeding 10 km.By revealing the magnetic fabric information preserved in Cenozoic within the basin,it is possible to reconstruct the regional tectonic stress orientation,which is of great significance for exploring the tectonic deformation and dynamic mechanism in the northern part of Qinghai-Xizang Plateau.The anisotropy of magnetic susceptibility in various directions of Cenozoic strata samples from Lulehe section in the northern Qaidam Basin was measured.Subsequently,magnetic fabric information was obtained from 1070 samples,and an analysis was conducted on the morphology of the magnetic fabric and its related parameters.The results show that the magnetic fabric of strata during 23.7-9.9 Ma in Lulehe section shows an initial deformation magnetic fabric,with its magnetic lineation indicating the direction of compression stress.The magnetic fabric of strata during 9.9-5.2 Ma is characterized by sedimentary fabric,and no obvious tectonic stress direction is recorded.After removing the effects of structural rotation using magnetic declination,variations are observed in the orientation of the compressive stress recorded by the magnetic fabric in Lulehe section over different periods,respectively.During 23.7-18.1 Ma,it gathers at~25°,revealing that the northern Qaidam Basin suffers from near SN compression stress in the Early Miocene.During 18.1-15.2 Ma,the direction of compressive stress rotates counterclockwise from~25°to~-20°.During 15.2-9.9 Ma,the direction of compressive stress rotates clockwise from~-20°to~20°.These results reveal that the compression stress direction of the northern Qaidam Basin first rotates counterclockwise(18.1-15.2 Ma)and then rotates clockwise(15.2-9.9 Ma)in the Middle Miocene.Based on the surrounding tectonic framework and the previous analysis of tectonic deformation,it is considered that the rotation of tectonic stress on the northern margin of Qaida
作者
许梦强
郑文俊
段磊
张博譞
李一格
杨俯尔
XU Meng-qiang;ZHENG Wen-jun;DUAN Lei;ZHANG Bo-xuan;LI Yi-ge;YANG Fu-er(School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,Zhuhai 519082,Guangdong,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,Guangdong,China;Railway Engineering Research Institute,China Academy of Railway Sciences Corporation Limited,Beijing 100081,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)
出处
《地球科学与环境学报》
CAS
北大核心
2024年第3期364-383,共20页
Journal of Earth Sciences and Environment
基金
第二次青藏高原综合科学考察研究项目(2019QZKK0901)
国家自然科学基金项目(41872204,42030301)。
关键词
磁组构
岩石磁学
构造应力
构造转换
新生代
柴达木盆地
magnetic fabric
rock magnetism
tectonic strain
tectonic transition
Cenozoic
Qaidam Basin
