GEOMETRY, KINEMATICS AND DYNAMICS OF THE HOUJIAYAO FAULT IN YANGYUAN COUNTY, HEBEI

The Houjiayao fault is a regional normal fault along the west border of the Yangyuan basin, which cuts through a part of the Quaternary and is covered by the Malan loess. It is characterized by a variety of associated and derived structural features and multi-periodical activities. Based on the geometric features and kinematic marks of the fault structures in the field and previous studies, there recognized three stages of tectonic activities. The first stage was suffered from a regional tension, the second stage from a short time regional extrusion and the third stage from a regional uplifting and depression. With regard to the dynamic mechanism, the activities of the fault were obviously droved by the uplifting of the Zhang-xuan mantle branch, the remote effect of the subduction of the Pacific plate and the deep process of rifting and-uplifting of the Fenwei rift. The evolution of the Yangyuan basin is reconstructed. It started from regional and rapid uplifting as a whole, then followed by further rifting of tectonic inversion-formed graben-mafic magmatic activities-formation of regional rifting mantle mat-gradual formation of the rift basin-a series of tectonic changes and a large circulation system for biological breeding.