Abstract:

The Chengkou-Fangxian fault zone is on the boundary of the Qinling Orogen and Yangtze Plate.The fault zone shows an arc-structure extruding towards SW, which composed the Dabashan tectonic arc. The macrostructures show that this fault zone thrusts strongly from north to south.The macrostructures and microstructures of these fault rocks reveal that the deformation mechanism of this fault zone is characterized by its brittle shallow. The finite strain measurements show that these rocks suffered a low-middle intensity deformation. Eleven quartz veins in the fault zone are dated by the Electron Spin Resonance(ESR), and their ages are distributed in the three stages (240-230 Ma,165-130 Ma,70- 60 Ma). Seven of them have ages from 165Ma to 130 Ma, indicating that the climax activity of this fault zone takes place at the Middle to Late Jurassic(165-130Ma).

Key words: Chengkou-Fangxian fault zone, the deformation characteristic, ESR dating