Fine Lithospheric Structure Beneath the Middle‐Southern Segment of the Tan‐Lu Fault Zone

Abstract

AbstractThe Tan‐Lu Fault Zone (TLFZ) is the largest active tectonic belt in East China, and it has a complicated history of formation and evolution. It is proved to have been playing an important dominant role in regional tectonics, magmatic activity, formation and distribution of mineral resources as well as current earthquake activities. To analyze the lithospheric structure of the TLFZ and blocks on both its sides, we applied deep seismic reflection exploration in the vicinity of Suqian City of Jiangsu Province in 2010, which is located at the middle‐southern segment of the TLFZ. The results show that the Moho and the bottom boundary of lithosphere are both west‐dipping, where the crustal thickness is about 31∼36 km and the lithosphere thickness is about 75∼86 km with an abrupt step around 10 km beneath the TLFZ. The TLFZ is characterized by a “flower‐like” structure consisting of many major faults on the seismic section. Inside them developed graben basin and compressive folds with tectonic traces of extension, compression and strike‐slip coexisting, which indicates that the formation and evolution of the TLFZ experienced multi‐period complicated tectonic movements. The TLFZ is a deep major fault system, cutting the near‐surface sediment layer downward to the Moho and the lithospheric mantle. The upwelling of high temperature and high pressure (HTHP) materials from the asthenosphere along the fault zone, magma under‐plating and thermal erosion lead to lithospheric extension and thinning, which probably change the lithospheric structure and material composition. This study can not only further our comprehension of the deep and shallow structures in the TLFZ, but also provide the data for analyzing the deep process and shallow structure in the eastern part of the North China Craton (NCC).