Abstract:

Abstract:  The Qinling LuonanLuanchuan fault belt shows the kinematic characteristics of a sinistral oblique subduction with strike generally at 107° and dip to north at 65°. The subduction of Southern China plate strikes at 80° and dips at 42°; the motion direction of Southern China plate is 42°; and the angle between the plate motion direction and the southern boundary of the North China plate is 65°, with the convergence angle of 25°. The fold hinge line trending 290° in strong deformation zone of the northern margin of the Qinling belt is 15° oblique to the strike of the LuonanLuanchuan fault belt. The strike of reverse thrust shares basically the same direction with the fold hinge line. The majority of faults and the LuonanLuanchuan belt have the same kinematic polarity; both are the leftlateral strikeslip reverse fault. The strikes of strikeslip normal faults are mainly NESW. The nature of faults, the direction of distribution and kinematic characteristics are in accordance with the mode of stress function of plate convergence; the schistosity and gneissosity are characterized by 117°trending and an angle of 10° existing between them and the LuonanLuanchuan fault belt. The systematic observation of rock deformation characteristics, strikedip survey of foliation, finite strain measurement of rocks and noncoaxial progressive deformation analysis of rocks were completed in vertical section of the shear plane. The results show that there is a tendency that the included angle between the foliation and the strike of shear zone is increasing from south to north in the strong deformation zone of the northern margin of the Qinling belt. The shearing strains of rocks are descending in file and the deformation of the orogenic belt shows a feature of “triclinic symmetry”.

Key words: Key words: Qinling orogenic belt; oblique convergence; strain partitioning; progressive deformation; convergence factor