Thrust and Nappe Tectonics in Qinling-Dabie Orogenic Belt, Central China

The Qinling-Tongbai-Dabie orogen is a typical collision orogen, tectonically composed of collision mélange belt, subduction crust wedge, overthrusting crust wedge, foreland fold-and-thrust belt and residual paleomarine basin. Its tectonic pattern is a large-scale thrust and nappe tectonics separated by several large-scale overthrusts which detached along different depths of the crust and moved from north to south. Six large-scale overthrusts are recognized in Qinling area, named the Luanchuan, Qinling, Shanyang, Wudang, Fangxian and Shennongjia overthrusts, respectively. Five large-scale overthrusts are discovered in Tingbai-Dabie area, titled alternatively the Tongbai, Feziling-Xinyang, Main Central, Suizhou-Taihu and Xiangfan-Guangji overthrusts. These overthrusts divide the orogen into several great thrusting sheets (nappes), in which thrust faults, ductile shear zones, imbricate structures, klippes and fensters occur and are destroyed by great brittle strike-slip faults. The kinematics of the thrust system indicates it moved form north to south under pure shear deformation mechanism. Detailed analysis is also done on the mylonite types, quartz fabrics, ultramicrostructures, balanced cross-sections, structural stress value, strain velocity, thrust timing, shearing temperature, depth and temperature of the detachment planes, and partial melting. The study on QB-1 seismic reflection cross-section in Qinling area and on the seismic wave anomaly in Dabie area shows that the lithosphere of Qinling-Dabie orogenic belt has a very complex composition and diversified layering and occurs low-velocity layers, which coincides with the large-scale detachment and thrust and nappe tectonics in the upper crust. The thermal mechanical rheological model is used to analogize the tectonic dynamics of the dabie thrust system. The test demonstrates that the heat originated from shearing and the thermal rheological features in the detachment plane is the critical inner mechanism although the plate convergent force is the driving force to move the plate. The petromechanics testing on the ductile shear zone indicates tat the high temperature and high strain represented b the plastic deformation lower the resistance against the shear deformation, resulting the long-distance thrusting in the crust. The elastic-plastic fault model and mantle-drag model are used to analyse the mechanism and process of the plate subduction and intercontinental collision, which demonstrates that the subduction and collision between the North China plate and the Yangtze plate are produced under bidirectional forces.

The large-scale thrust and nappe tectonics in the Qinling-Dabie orogenic belt are systematically and comprehensively studied by the analysis of geological structures, petrology, geophysics, mathematical and physical modeling and experimental analogue, which will theoretically contributes to the establishment and development of the crust tectonic dynamics, and will practically be an important guide to the explanation of the geological evolution and to the development of mineral resources in Qinling-Dabie are. This book may be referenced by students, teachers and researchers dealing with the tectonics, geophysics, experimental structural geology, petromechanics and so on.

Contents

1. Division of Tectonic Units in Qinling-Dabie Orogenic Belt
2. Thrust and Nappe Tectonic Pattern in Qinling Orogenic Belt
3. Thrust and Nappe Tectonic Pattern in Tongbai-Dabie Orogenic Belt
4. Kinematics and Dynamics of Thrust and Nappe Tectonics in Qinling-Dabie and
Qinling orogenic belts
5. Geophysical Field in Qinling-Dabie Orogenic Belt
6. Mathematical and Physical Modelling on Large-scale Thrust and Nappe
Tectonics in Qinling-Dabie Area
7. Tectonic Evolution of Qinling-Dabie Orogenic Belt
8. Summary
9. References